Remove support for binary over SSE and add transfer format to negotiation (#1564)

benchmarks/Microsoft.AspNetCore.SignalR.Microbenchmarks/BroadcastBenchmark.cs

@@ -5,7 +5,6 @@ using System.Threading.Channels;
 using System.Threading.Tasks;
 using BenchmarkDotNet.Attributes;
 using Microsoft.AspNetCore.SignalR.Internal;
-using Microsoft.AspNetCore.SignalR.Internal.Encoders;
 using Microsoft.AspNetCore.SignalR.Internal.Protocol;
 using Microsoft.AspNetCore.Sockets;
 using Microsoft.Extensions.Logging.Abstractions;
@@ -40,14 +39,12 @@ namespace Microsoft.AspNetCore.SignalR.Microbenchmarks
                 protocol = new MessagePackHubProtocol();
             }
 
-            var encoder = new PassThroughEncoder();
-
             for (var i = 0; i < Connections; ++i)
             {
                 var pair = DuplexPipe.CreateConnectionPair(PipeOptions.Default, PipeOptions.Default);
                 var connection = new DefaultConnectionContext(Guid.NewGuid().ToString(), pair.Application, pair.Transport);
                 var hubConnection = new HubConnectionContext(connection, Timeout.InfiniteTimeSpan, NullLoggerFactory.Instance);
-                hubConnection.ProtocolReaderWriter = new HubProtocolReaderWriter(protocol, encoder);
+                hubConnection.Protocol = protocol;
                 _hubLifetimeManager.OnConnectedAsync(hubConnection).Wait();
             }
 

benchmarks/Microsoft.AspNetCore.SignalR.Microbenchmarks/DefaultHubDispatcherBenchmark.cs

@@ -1,4 +1,4 @@
-// Copyright (c) .NET Foundation. All rights reserved.
+// Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
@@ -11,12 +11,11 @@ using System.Threading.Tasks;
 using BenchmarkDotNet.Attributes;
 using Microsoft.AspNetCore.Protocols;
 using Microsoft.AspNetCore.SignalR.Internal;
-using Microsoft.AspNetCore.SignalR.Internal.Encoders;
 using Microsoft.AspNetCore.SignalR.Internal.Protocol;
+using Microsoft.AspNetCore.Sockets;
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Logging;
 using Microsoft.Extensions.Logging.Abstractions;
-using Moq;
 using DefaultConnectionContext = Microsoft.AspNetCore.Sockets.DefaultConnectionContext;
 
 namespace Microsoft.AspNetCore.SignalR.Microbenchmarks
@@ -47,13 +46,13 @@ namespace Microsoft.AspNetCore.SignalR.Microbenchmarks
 
             _connectionContext = new NoErrorHubConnectionContext(connection, TimeSpan.Zero, NullLoggerFactory.Instance);
 
-            _connectionContext.ProtocolReaderWriter = new HubProtocolReaderWriter(new FakeHubProtocol(), new FakeDataEncoder());
+            _connectionContext.Protocol = new FakeHubProtocol();
         }
 
         public class FakeHubProtocol : IHubProtocol
         {
             public string Name { get; }
-            public ProtocolType Type { get; }
+            public TransferFormat TransferFormat { get; }
 
             public bool TryParseMessages(ReadOnlySpan<byte> input, IInvocationBinder binder, IList<HubMessage> messages)
             {
@@ -65,19 +64,6 @@ namespace Microsoft.AspNetCore.SignalR.Microbenchmarks
             }
         }
 
-        public class FakeDataEncoder : IDataEncoder
-        {
-            public byte[] Encode(byte[] payload)
-            {
-                return null;
-            }
-
-            public bool TryDecode(ref ReadOnlySpan<byte> buffer, out ReadOnlySpan<byte> data)
-            {
-                return false;
-            }
-        }
-
         public class NoErrorHubConnectionContext : HubConnectionContext
         {
             public NoErrorHubConnectionContext(ConnectionContext connectionContext, TimeSpan keepAliveInterval, ILoggerFactory loggerFactory) : base(connectionContext, keepAliveInterval, loggerFactory)
@@ -232,4 +218,4 @@ namespace Microsoft.AspNetCore.SignalR.Microbenchmarks
             return _dispatcher.DispatchMessageAsync(_connectionContext, new StreamInvocationMessage("123", "StreamChannelReaderValueTaskAsync", null));
         }
     }
-}
+}

benchmarks/Microsoft.AspNetCore.SignalR.Microbenchmarks/HubProtocolBenchmark.cs

@@ -2,16 +2,17 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
+using System.Collections.Generic;
+using System.IO;
 using BenchmarkDotNet.Attributes;
 using Microsoft.AspNetCore.SignalR.Internal;
-using Microsoft.AspNetCore.SignalR.Internal.Encoders;
 using Microsoft.AspNetCore.SignalR.Internal.Protocol;
 
 namespace Microsoft.AspNetCore.SignalR.Microbenchmarks
 {
     public class HubProtocolBenchmark
     {
-        private HubProtocolReaderWriter _hubProtocolReaderWriter;
+        private IHubProtocol _hubProtocol;
         private byte[] _binaryInput;
         private TestBinder _binder;
         private HubMessage _hubMessage;
@@ -28,10 +29,10 @@ namespace Microsoft.AspNetCore.SignalR.Microbenchmarks
             switch (HubProtocol)
             {
                 case Protocol.MsgPack:
-                    _hubProtocolReaderWriter = new HubProtocolReaderWriter(new MessagePackHubProtocol(), new PassThroughEncoder());
+                    _hubProtocol = new MessagePackHubProtocol();
                     break;
                 case Protocol.Json:
-                    _hubProtocolReaderWriter = new HubProtocolReaderWriter(new JsonHubProtocol(), new PassThroughEncoder());
+                    _hubProtocol = new JsonHubProtocol();
                     break;
             }
 
@@ -51,14 +52,15 @@ namespace Microsoft.AspNetCore.SignalR.Microbenchmarks
                     break;
             }
 
-            _binaryInput = GetBytes(_hubMessage);
+            _binaryInput = _hubProtocol.WriteToArray(_hubMessage);
             _binder = new TestBinder(_hubMessage);
         }
 
         [Benchmark]
         public void ReadSingleMessage()
         {
-            if (!_hubProtocolReaderWriter.ReadMessages(_binaryInput, _binder, out var _))
+            var messages = new List<HubMessage>();
+            if (!_hubProtocol.TryParseMessages(_binaryInput, _binder, messages))
             {
                 throw new InvalidOperationException("Failed to read message");
             }
@@ -67,7 +69,8 @@ namespace Microsoft.AspNetCore.SignalR.Microbenchmarks
         [Benchmark]
         public void WriteSingleMessage()
         {
-            if (_hubProtocolReaderWriter.WriteMessage(_hubMessage).Length != _binaryInput.Length)
+            var bytes = _hubProtocol.WriteToArray(_hubMessage);
+            if (bytes.Length != _binaryInput.Length)
             {
                 throw new InvalidOperationException("Failed to write message");
             }
@@ -86,10 +89,5 @@ namespace Microsoft.AspNetCore.SignalR.Microbenchmarks
             ManyArguments = 2,
             LargeArguments = 3
         }
-
-        private byte[] GetBytes(HubMessage hubMessage)
-        {
-            return _hubProtocolReaderWriter.WriteMessage(_hubMessage);
-        }
     }
 }

client-ts/FunctionalTests/ts/HubConnectionTests.ts

@@ -521,6 +521,42 @@ describe("hubConnection", () => {
         });
     });
 
+    if (typeof EventSource !== "undefined") {
+        it("allows Server-Sent Events when negotiating for JSON protocol", async (done) => {
+            const hubConnection = new HubConnection(TESTHUB_NOWEBSOCKETS_ENDPOINT_URL, {
+                logger: LogLevel.Trace,
+                protocol: new JsonHubProtocol(),
+            });
+
+            try {
+                await hubConnection.start();
+
+                // Check what transport was used by asking the server to tell us.
+                expect(await hubConnection.invoke("GetActiveTransportName")).toEqual("ServerSentEvents");
+                done();
+            } catch (e) {
+                fail(e);
+            }
+        });
+    }
+
+    it("skips Server-Sent Events when negotiating for MsgPack protocol", async (done) => {
+        const hubConnection = new HubConnection(TESTHUB_NOWEBSOCKETS_ENDPOINT_URL, {
+            logger: LogLevel.Trace,
+            protocol: new MessagePackHubProtocol(),
+        });
+
+        try {
+            await hubConnection.start();
+
+            // Check what transport was used by asking the server to tell us.
+            expect(await hubConnection.invoke("GetActiveTransportName")).toEqual("LongPolling");
+            done();
+        } catch (e) {
+            fail(e);
+        }
+    });
+
     function getJwtToken(url): Promise<string> {
         return new Promise((resolve, reject) => {
             const xhr = new XMLHttpRequest();

client-ts/FunctionalTests/web.config

@@ -1,14 +1,12 @@
 <?xml version="1.0" encoding="utf-8"?>
 <configuration>
-
   <!--
     Configure your application settings in appsettings.json. Learn more at http://go.microsoft.com/fwlink/?LinkId=786380
   -->
-
   <system.webServer>
     <handlers>
-      <add name="aspNetCore" path="*" verb="*" modules="AspNetCoreModule" resourceType="Unspecified"/>
+      <add name="aspNetCore" path="*" verb="*" modules="AspNetCoreModule" resourceType="Unspecified" />
     </handlers>
-    <aspNetCore processPath="%LAUNCHER_PATH%" arguments="%LAUNCHER_ARGS%" stdoutLogEnabled="false" stdoutLogFile=".\logs\stdout" forwardWindowsAuthToken="false"/>
+    <aspNetCore processPath="%LAUNCHER_PATH%" arguments="%LAUNCHER_ARGS%" stdoutLogEnabled="false" stdoutLogFile=".\logs\stdout" forwardWindowsAuthToken="false" startupTimeLimit="3600" requestTimeout="23:00:00" />
   </system.webServer>
-</configuration>
+</configuration>

client-ts/signalr-protocol-msgpack/package-lock.json

@@ -1,9 +1,18 @@
 {
   "name": "@aspnet/signalr-protocol-msgpack",
-  "version": "1.0.0-preview2-t000",
+  "version": "1.0.0-preview1-t000",
   "lockfileVersion": 1,
   "requires": true,
   "dependencies": {
+    "@aspnet/signalr": {
+      "version": "file:../signalr",
+      "dependencies": {
+        "es6-promise": {
+          "version": "4.2.2",
+          "bundled": true
+        }
+      }
+    },
     "@types/bl": {
       "version": "0.8.31",
       "resolved": "https://registry.npmjs.org/@types/bl/-/bl-0.8.31.tgz",

client-ts/signalr-protocol-msgpack/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@aspnet/signalr-protocol-msgpack",
-  "version": "1.0.0-preview1-t000",
+  "version": "1.0.0-preview2-t000",
   "description": "MsgPack Protocol support for ASP.NET Core SignalR",
   "main": "./dist/cjs/index.js",
   "browser": "./dist/browser/signalr-protocol-msgpack.js",
@@ -18,8 +18,8 @@
     "build:cjs": "node ../node_modules/typescript/bin/tsc --project ./tsconfig.json --module commonjs --outDir ./dist/cjs --target ES5",
     "build:browser": "node ../node_modules/rollup/bin/rollup -c",
     "build:uglify": "node ../node_modules/uglify-js/bin/uglifyjs --source-map \"url='signalr-protocol-msgpack.min.js.map',content='./dist/browser/signalr-protocol-msgpack.js.map'\" --comments -o ./dist/browser/signalr-protocol-msgpack.min.js ./dist/browser/signalr-protocol-msgpack.js",
-    "pretest": "node ../node_modules/rimraf/bin.js ./spec/obj && node ../node_modules/typescript/bin/tsc --project ./spec/tsconfig.json",
+    "pretest": "node ../node_modules/rimraf/bin.js ./spec/obj && node ../node_modules/typescript/bin/tsc --project ./spec/tsconfig.json && cd ./spec/obj/src && npm init -y && npm install ../../../../signalr",
-    "test": "node ../node_modules/jasmine/bin/jasmine.js ./spec/obj/signalr-protocol-msgpack/spec/**/*.spec.js"
+    "test": "node ../node_modules/jasmine/bin/jasmine.js ./spec/obj/spec/**/*.spec.js"
   },
   "keywords": [
     "signalr",

client-ts/signalr-protocol-msgpack/spec/tsconfig.json

@@ -8,7 +8,7 @@
         "lib": [ "es2015", "dom" ],
         "baseUrl": ".",
         "paths": {
-            "@aspnet/signalr": [ "../../signalr/src/index" ]
+            "@aspnet/*": [ "../../*" ]
         }
     },
     "include": [

client-ts/signalr-protocol-msgpack/src/MessagePackHubProtocol.ts

@@ -1,7 +1,7 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
-import { CompletionMessage, HubMessage, IHubProtocol, InvocationMessage, MessageHeaders, MessageType, ProtocolType, StreamInvocationMessage, StreamItemMessage } from "@aspnet/signalr";
+import { CompletionMessage, HubMessage, IHubProtocol, InvocationMessage, MessageHeaders, MessageType, StreamInvocationMessage, StreamItemMessage, TransferFormat } from "@aspnet/signalr";
 import { Buffer } from "buffer";
 import * as msgpack5 from "msgpack5";
 import { BinaryMessageFormat } from "./BinaryMessageFormat";
@@ -10,7 +10,7 @@ export class MessagePackHubProtocol implements IHubProtocol {
 
     public readonly name: string = "messagepack";
 
-    public readonly type: ProtocolType = ProtocolType.Binary;
+    public readonly transferFormat: TransferFormat = TransferFormat.Binary;
 
     public parseMessages(input: ArrayBuffer): HubMessage[] {
         return BinaryMessageFormat.parse(input).map((m) => this.parseMessage(m));

client-ts/signalr/package-lock.json

@@ -1,6 +1,6 @@
 {
   "name": "@aspnet/signalr",
-  "version": "1.0.0-preview2-t000",
+  "version": "1.0.0-preview1-t000",
   "lockfileVersion": 1,
   "requires": true,
   "dependencies": {

client-ts/signalr/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@aspnet/signalr",
-  "version": "1.0.0-preview1-t000",
+  "version": "1.0.0-preview2-t000",
   "description": "ASP.NET Core SignalR Client",
   "main": "./dist/cjs/index.js",
   "browser": "./dist/browser/signalr.js",

client-ts/signalr/spec/Base64EncodedHubProtocol.spec.ts

@@ -1,74 +0,0 @@
-// Copyright (c) .NET Foundation. All rights reserved.
-// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
-
-import { Base64EncodedHubProtocol } from "../src/Base64EncodedHubProtocol";
-import { HubMessage, IHubProtocol, ProtocolType } from "../src/IHubProtocol";
-
-class FakeHubProtocol implements IHubProtocol {
-    public name: "fakehubprotocol";
-    public type: ProtocolType;
-
-    public parseMessages(input: any): HubMessage[] {
-        let s = "";
-
-        new Uint8Array(input).forEach((item: any) => {
-            s += String.fromCharCode(item);
-        });
-
-        return JSON.parse(s);
-    }
-
-    public writeMessage(message: HubMessage): any {
-        const s = JSON.stringify(message);
-        const payload = new Uint8Array(s.length);
-        for (let i = 0; i < payload.length; i++) {
-            payload[i] = s.charCodeAt(i);
-        }
-        return payload;
-    }
-}
-
-describe("Base64EncodedHubProtocol", () => {
-    ([
-        ["ABC", new Error("Invalid payload.")],
-        ["3:ABC", new Error("Invalid payload.")],
-        [":;", new Error("Invalid length: ''")],
-        ["1.0:A;", new Error("Invalid length: '1.0'")],
-        ["2:A;", new Error("Invalid message size.")],
-        ["2:ABC;", new Error("Invalid message size.")],
-    ] as Array<[string, Error]>).forEach(([payload, expectedError]) => {
-        it(`should fail to parse '${payload}'`, () => {
-            expect(() => new Base64EncodedHubProtocol(new FakeHubProtocol()).parseMessages(payload)).toThrow(expectedError);
-        });
-    });
-
-    ([
-        ["2:{};", {}],
-    ] as [[string, any]]).forEach(([payload, message]) => {
-        it(`should be able to parse '${payload}'`, () => {
-
-            const globalAny: any = global;
-            globalAny.atob = (input: any) => input;
-
-            const result = new Base64EncodedHubProtocol(new FakeHubProtocol()).parseMessages(payload);
-            expect(result).toEqual(message);
-
-            delete globalAny.atob;
-        });
-    });
-
-    ([
-        [{}, "2:{};"],
-    ] as Array<[any, string]>).forEach(([message, payload]) => {
-        it(`should be able to write '${JSON.stringify(message)}'`, () => {
-
-            const globalAny: any = global;
-            globalAny.btoa = (input: any) => input;
-
-            const result = new Base64EncodedHubProtocol(new FakeHubProtocol()).writeMessage(message);
-            expect(result).toEqual(payload);
-
-            delete globalAny.btoa;
-        });
-    });
-});

client-ts/signalr/spec/HttpConnection.spec.ts

@@ -5,7 +5,7 @@ import { DataReceived, TransportClosed } from "../src/Common";
 import { HttpConnection } from "../src/HttpConnection";
 import { IHttpConnectionOptions } from "../src/HttpConnection";
 import { HttpResponse } from "../src/index";
-import { ITransport, TransferMode, TransportType } from "../src/Transports";
+import { ITransport, TransferFormat, TransportType } from "../src/Transports";
 import { eachEndpointUrl, eachTransport } from "./Common";
 import { TestHttpClient } from "./TestHttpClient";
 
@@ -15,13 +15,13 @@ const commonOptions: IHttpConnectionOptions = {
 
 describe("HttpConnection", () => {
     it("cannot be created with relative url if document object is not present", () => {
-        expect(() => new HttpConnection("/test", commonOptions))
+        expect(() => new HttpConnection("/test", TransferFormat.Text, commonOptions))
             .toThrow(new Error("Cannot resolve '/test'."));
     });
 
     it("cannot be created with relative url if window object is not present", () => {
         (global as any).window = {};
-        expect(() => new HttpConnection("/test", commonOptions))
+        expect(() => new HttpConnection("/test", TransferFormat.Text, commonOptions))
             .toThrow(new Error("Cannot resolve '/test'."));
         delete (global as any).window;
     });
@@ -34,7 +34,7 @@ describe("HttpConnection", () => {
                 .on("GET", (r) => ""),
         } as IHttpConnectionOptions;
 
-        const connection = new HttpConnection("http://tempuri.org", options);
+        const connection = new HttpConnection("http://tempuri.org", TransferFormat.Text, options);
 
         try {
             await connection.start();
@@ -64,7 +64,7 @@ describe("HttpConnection", () => {
                 }),
         } as IHttpConnectionOptions;
 
-        const connection = new HttpConnection("http://tempuri.org", options);
+        const connection = new HttpConnection("http://tempuri.org", TransferFormat.Text, options);
 
         try {
             await connection.start();
@@ -86,7 +86,7 @@ describe("HttpConnection", () => {
                 .on("GET", (r) => ""),
         } as IHttpConnectionOptions;
 
-        const connection = new HttpConnection("http://tempuri.org", options);
+        const connection = new HttpConnection("http://tempuri.org", TransferFormat.Text, options);
 
         try {
             await connection.start();
@@ -117,7 +117,7 @@ describe("HttpConnection", () => {
                 }),
         } as IHttpConnectionOptions;
 
-        const connection = new HttpConnection("http://tempuri.org", options);
+        const connection = new HttpConnection("http://tempuri.org", TransferFormat.Text, options);
 
         try {
             await connection.start();
@@ -129,17 +129,17 @@ describe("HttpConnection", () => {
     });
 
     it("can stop a non-started connection", async (done) => {
-        const connection = new HttpConnection("http://tempuri.org", commonOptions);
+        const connection = new HttpConnection("http://tempuri.org", TransferFormat.Text, commonOptions);
         await connection.stop();
         done();
     });
 
-    it("preserves users connection string", async (done) => {
+    it("preserves user's query string", async (done) => {
         let connectUrl: string;
         const fakeTransport: ITransport = {
-            connect(url: string): Promise<TransferMode> {
+            connect(url: string): Promise<void> {
                 connectUrl = url;
-                return Promise.reject(TransferMode.Text);
+                return Promise.reject("");
             },
             send(data: any): Promise<void> {
                 return Promise.reject("");
@@ -159,7 +159,7 @@ describe("HttpConnection", () => {
             transport: fakeTransport,
         } as IHttpConnectionOptions;
 
-        const connection = new HttpConnection("http://tempuri.org?q=myData", options);
+        const connection = new HttpConnection("http://tempuri.org?q=myData", TransferFormat.Text, options);
 
         try {
             await connection.start();
@@ -190,7 +190,7 @@ describe("HttpConnection", () => {
                     }),
             } as IHttpConnectionOptions;
 
-            connection = new HttpConnection(givenUrl, options);
+            connection = new HttpConnection(givenUrl, TransferFormat.Text, options);
 
             try {
                 await connection.start();
@@ -213,18 +213,18 @@ describe("HttpConnection", () => {
             const options: IHttpConnectionOptions = {
                 ...commonOptions,
                 httpClient: new TestHttpClient()
-                    .on("POST", (r) => "{ \"connectionId\": \"42\", \"availableTransports\": [] }")
+                    .on("POST", (r) => ({ connectionId: "42", availableTransports: [] }))
                     .on("GET", (r) => ""),
                 transport: requestedTransport,
             } as IHttpConnectionOptions;
 
-            const connection = new HttpConnection("http://tempuri.org", options);
+            const connection = new HttpConnection("http://tempuri.org", TransferFormat.Text, options);
             try {
                 await connection.start();
                 fail();
                 done();
             } catch (e) {
-                expect(e.message).toBe("No available transports found.");
+                expect(e.message).toBe("Unable to initialize any of the available transports.");
                 done();
             }
         });
@@ -234,17 +234,17 @@ describe("HttpConnection", () => {
         const options: IHttpConnectionOptions = {
             ...commonOptions,
             httpClient: new TestHttpClient()
-                .on("POST", (r) => "{ \"connectionId\": \"42\", \"availableTransports\": [] }")
+                .on("POST", (r) => ({ connectionId: "42", availableTransports: [] }))
                 .on("GET", (r) => ""),
         } as IHttpConnectionOptions;
 
-        const connection = new HttpConnection("http://tempuri.org", options);
+        const connection = new HttpConnection("http://tempuri.org", TransferFormat.Text, options);
         try {
             await connection.start();
             fail();
             done();
         } catch (e) {
-            expect(e.message).toBe("No available transports found.");
+            expect(e.message).toBe("Unable to initialize any of the available transports.");
             done();
         }
     });
@@ -256,7 +256,7 @@ describe("HttpConnection", () => {
             transport: TransportType.WebSockets,
         } as IHttpConnectionOptions;
 
-        const connection = new HttpConnection("http://tempuri.org", options);
+        const connection = new HttpConnection("http://tempuri.org", TransferFormat.Text, options);
         try {
             await connection.start();
             fail();
@@ -264,42 +264,24 @@ describe("HttpConnection", () => {
         } catch (e) {
             // WebSocket is created when the transport is connecting which happens after
             // negotiate request would be sent. No better/easier way to test this.
-            expect(e.message).toBe("WebSocket is not defined");
+            expect(e.message).toBe("'WebSocket' is not supported in your environment.");
             done();
         }
     });
 
-    [
+    describe(".constructor", () => {
-        [TransferMode.Text, TransferMode.Text],
+        it("throws if no Url is provided", async () => {
-        [TransferMode.Text, TransferMode.Binary],
+            // Force TypeScript to let us call the constructor incorrectly :)
-        [TransferMode.Binary, TransferMode.Text],
+            expect(() => new (HttpConnection as any)()).toThrowError("The 'url' argument is required.");
-        [TransferMode.Binary, TransferMode.Binary],
+        });
-    ].forEach(([requestedTransferMode, transportTransferMode]) => {
-        it(`connection returns ${transportTransferMode} transfer mode when ${requestedTransferMode} transfer mode is requested`, async () => {
-            const fakeTransport = {
-                // mode: TransferMode : TransferMode.Text
-                connect(url: string, requestedTransferMode: TransferMode): Promise<TransferMode> { return Promise.resolve(transportTransferMode); },
-                mode: transportTransferMode,
-                onclose: null,
-                onreceive: null,
-                send(data: any): Promise<void> { return Promise.resolve(); },
-                stop(): Promise<void> { return Promise.resolve(); },
-            } as ITransport;
 
-            const options: IHttpConnectionOptions = {
+        it("throws if no TransferFormat is provided", async () => {
-                ...commonOptions,
+            // Force TypeScript to let us call the constructor incorrectly :)
-                httpClient: new TestHttpClient()
+            expect(() => new (HttpConnection as any)("http://tempuri.org")).toThrowError("The 'transferFormat' argument is required.");
-                    .on("POST", (r) => "{ \"connectionId\": \"42\", \"availableTransports\": [] }")
+        });
-                    .on("GET", (r) => ""),
-                transport: fakeTransport,
-            } as IHttpConnectionOptions;
 
-            const connection = new HttpConnection("https://tempuri.org", options);
+        it("throws if an unsupported TransferFormat is provided", async () => {
-            connection.features.transferMode = requestedTransferMode;
+            expect(() => new HttpConnection("http://tempuri.org", 42)).toThrowError("Unknown transferFormat value: 42.");
-            await connection.start();
-            const actualTransferMode = connection.features.transferMode;
-
-            expect(actualTransferMode).toBe(transportTransferMode);
         });
     });
 });

client-ts/signalr/spec/HubConnection.spec.ts

@@ -8,7 +8,7 @@ import { MessageType } from "../src/IHubProtocol";
 import { ILogger, LogLevel } from "../src/ILogger";
 import { Observer } from "../src/Observable";
 import { TextMessageFormat } from "../src/TextMessageFormat";
-import { ITransport, TransferMode, TransportType } from "../src/Transports";
+import { ITransport, TransferFormat, TransportType } from "../src/Transports";
 
 import { IHubConnectionOptions } from "../src/HubConnection";
 import { asyncit as it, captureException, delay, PromiseSource } from "./Utils";

client-ts/signalr/spec/TestHttpClient.ts

@@ -3,7 +3,7 @@
 
 import { HttpClient, HttpRequest, HttpResponse } from "../src/HttpClient";
 
-type TestHttpHandlerResult = HttpResponse | string;
+type TestHttpHandlerResult = any;
 export type TestHttpHandler = (request: HttpRequest, next?: (request: HttpRequest) => Promise<HttpResponse>) => Promise<TestHttpHandlerResult> | TestHttpHandlerResult;
 
 export class TestHttpClient extends HttpClient {
@@ -57,9 +57,14 @@ export class TestHttpClient extends HttpClient {
                 }
 
                 if (typeof val === "string") {
+                    // string payload
                     return new HttpResponse(200, "OK", val);
+                } else if(typeof val === "object" && val.statusCode) {
+                    // HttpResponse payload
+                    return val as HttpResponse;
                 } else {
-                    return val;
+                    // JSON payload
+                    return new HttpResponse(200, "OK", JSON.stringify(val));
                 }
             } else {
                 return await oldHandler(request);

client-ts/signalr/spec/Utils.ts

@@ -56,4 +56,4 @@ export class PromiseSource<T> {
     public reject(reason?: any) {
         this.rejecter(reason);
     }
-}
+}

client-ts/signalr/src/Base64EncodedHubProtocol.ts

@@ -1,60 +0,0 @@
-// Copyright (c) .NET Foundation. All rights reserved.
-// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
-
-import { HubMessage, IHubProtocol, ProtocolType } from "./IHubProtocol";
-
-export class Base64EncodedHubProtocol implements IHubProtocol {
-    private wrappedProtocol: IHubProtocol;
-
-    constructor(protocol: IHubProtocol) {
-        this.wrappedProtocol = protocol;
-        this.name = this.wrappedProtocol.name;
-        this.type = ProtocolType.Text;
-    }
-
-    public readonly name: string;
-    public readonly type: ProtocolType;
-
-    public parseMessages(input: any): HubMessage[] {
-        // The format of the message is `size:message;`
-        const pos = input.indexOf(":");
-        if (pos === -1 || input[input.length - 1] !== ";") {
-            throw new Error("Invalid payload.");
-        }
-
-        const lenStr = input.substring(0, pos);
-        if (!/^[0-9]+$/.test(lenStr)) {
-            throw new Error(`Invalid length: '${lenStr}'`);
-        }
-
-        const messageSize = parseInt(lenStr, 10);
-        // 2 accounts for ':' after message size and trailing ';'
-        if (messageSize !== input.length - pos - 2) {
-            throw new Error("Invalid message size.");
-        }
-
-        const encodedMessage = input.substring(pos + 1, input.length - 1);
-
-        // atob/btoa are browsers APIs but they can be polyfilled. If this becomes problematic we can use
-        // base64-js module
-        const s = atob(encodedMessage);
-        const payload = new Uint8Array(s.length);
-        for (let i = 0; i < payload.length; i++) {
-            payload[i] = s.charCodeAt(i);
-        }
-        return this.wrappedProtocol.parseMessages(payload.buffer);
-    }
-
-    public writeMessage(message: HubMessage): any {
-        const payload = new Uint8Array(this.wrappedProtocol.writeMessage(message));
-        let s = "";
-        for (let i = 0; i < payload.byteLength; i++) {
-            s += String.fromCharCode(payload[i]);
-        }
-        // atob/btoa are browsers APIs but they can be polyfilled. If this becomes problematic we can use
-        // base64-js module
-        const encodedMessage = btoa(s);
-
-        return `${encodedMessage.length.toString()}:${encodedMessage};`;
-    }
-}

client-ts/signalr/src/HttpConnection.ts

@@ -6,7 +6,8 @@ import { DefaultHttpClient, HttpClient } from "./HttpClient";
 import { IConnection } from "./IConnection";
 import { ILogger, LogLevel } from "./ILogger";
 import { LoggerFactory } from "./Loggers";
-import { ITransport, LongPollingTransport, ServerSentEventsTransport, TransferMode, TransportType, WebSocketTransport } from "./Transports";
+import { ITransport, LongPollingTransport, ServerSentEventsTransport, TransferFormat, TransportType, WebSocketTransport } from "./Transports";
+import { Arg } from "./Utils";
 
 export interface IHttpConnectionOptions {
     httpClient?: HttpClient;
@@ -23,7 +24,12 @@ const enum ConnectionState {
 
 interface INegotiateResponse {
     connectionId: string;
-    availableTransports: string[];
+    availableTransports: IAvailableTransport[];
+}
+
+interface IAvailableTransport {
+    transport: keyof typeof TransportType;
+    transferFormats: Array<keyof typeof TransferFormat>;
 }
 
 export class HttpConnection implements IConnection {
@@ -33,13 +39,19 @@ export class HttpConnection implements IConnection {
     private readonly httpClient: HttpClient;
     private readonly logger: ILogger;
     private readonly options: IHttpConnectionOptions;
+    private readonly transferFormat: TransferFormat;
     private transport: ITransport;
     private connectionId: string;
     private startPromise: Promise<void>;
 
     public readonly features: any = {};
 
-    constructor(url: string, options: IHttpConnectionOptions = {}) {
+    constructor(url: string, transferFormat: TransferFormat, options: IHttpConnectionOptions = {}) {
+        Arg.isRequired(url, "url");
+        Arg.isRequired(transferFormat, "transferFormat");
+        Arg.isIn(transferFormat, TransferFormat, "transferFormat");
+
+        this.transferFormat = transferFormat;
         this.logger = LoggerFactory.createLogger(options.logger);
         this.baseUrl = this.resolveUrl(url);
 
@@ -67,7 +79,7 @@ export class HttpConnection implements IConnection {
             if (this.options.transport === TransportType.WebSockets) {
                 // No need to add a connection ID in this case
                 this.url = this.baseUrl;
-                this.transport = this.createTransport(this.options.transport, [TransportType[TransportType.WebSockets]]);
+                this.transport = this.constructTransport(TransportType.WebSockets);
             } else {
                 let headers;
                 const token = this.options.accessTokenFactory();
@@ -91,50 +103,73 @@ export class HttpConnection implements IConnection {
 
                 if (this.connectionId) {
                     this.url = this.baseUrl + (this.baseUrl.indexOf("?") === -1 ? "?" : "&") + `id=${this.connectionId}`;
-                    this.transport = this.createTransport(this.options.transport, negotiateResponse.availableTransports);
+                    this.transport = this.createTransport(this.options.transport, negotiateResponse.availableTransports, this.transferFormat);
                 }
             }
 
             this.transport.onreceive = this.onreceive;
             this.transport.onclose = (e) => this.stopConnection(true, e);
 
-            const requestedTransferMode =
+            await this.transport.connect(this.url, this.transferFormat, this);
-                this.features.transferMode === TransferMode.Binary
-                    ? TransferMode.Binary
-                    : TransferMode.Text;
-
-            this.features.transferMode = await this.transport.connect(this.url, requestedTransferMode, this);
 
             // only change the state if we were connecting to not overwrite
             // the state if the connection is already marked as Disconnected
             this.changeState(ConnectionState.Connecting, ConnectionState.Connected);
         } catch (e) {
-            this.logger.log(LogLevel.Error, "Failed to start the connection. " + e);
+            this.logger.log(LogLevel.Error, "Failed to start the connection: " + e);
             this.connectionState = ConnectionState.Disconnected;
             this.transport = null;
             throw e;
         }
     }
 
-    private createTransport(transport: TransportType | ITransport, availableTransports: string[]): ITransport {
+    private createTransport(requestedTransport: TransportType | ITransport, availableTransports: IAvailableTransport[], requestedTransferFormat: TransferFormat): ITransport {
-        if ((transport === null || transport === undefined) && availableTransports.length > 0) {
+        if (this.isITransport(requestedTransport)) {
-            transport = TransportType[availableTransports[0]];
+            this.logger.log(LogLevel.Trace, "Connection was provided an instance of ITransport, using that directly.");
-        }
+            return requestedTransport;
-        if (transport === TransportType.WebSockets && availableTransports.indexOf(TransportType[transport]) >= 0) {
-            return new WebSocketTransport(this.options.accessTokenFactory, this.logger);
-        }
-        if (transport === TransportType.ServerSentEvents && availableTransports.indexOf(TransportType[transport]) >= 0) {
-            return new ServerSentEventsTransport(this.httpClient, this.options.accessTokenFactory, this.logger);
-        }
-        if (transport === TransportType.LongPolling && availableTransports.indexOf(TransportType[transport]) >= 0) {
-            return new LongPollingTransport(this.httpClient, this.options.accessTokenFactory, this.logger);
         }
 
-        if (this.isITransport(transport)) {
+        for (const endpoint of availableTransports) {
-            return transport;
+            const transport = this.resolveTransport(endpoint, requestedTransport, requestedTransferFormat);
+            if (transport) {
+                return this.constructTransport(transport);
+            }
         }
 
-        throw new Error("No available transports found.");
+        throw new Error("Unable to initialize any of the available transports.");
+    }
+
+    private constructTransport(transport: TransportType) {
+        switch (transport) {
+            case TransportType.WebSockets:
+                return new WebSocketTransport(this.options.accessTokenFactory, this.logger);
+            case TransportType.ServerSentEvents:
+                return new ServerSentEventsTransport(this.httpClient, this.options.accessTokenFactory, this.logger);
+            case TransportType.LongPolling:
+                return new LongPollingTransport(this.httpClient, this.options.accessTokenFactory, this.logger);
+            default:
+                throw new Error(`Unknown transport: ${transport}.`);
+        }
+    }
+
+    private resolveTransport(endpoint: IAvailableTransport, requestedTransport: TransportType, requestedTransferFormat: TransferFormat): TransportType | null {
+        const transport = TransportType[endpoint.transport];
+        if (!transport) {
+            this.logger.log(LogLevel.Trace, `Skipping transport '${endpoint.transport}' because it is not supported by this client.`);
+        } else {
+            const transferFormats = endpoint.transferFormats.map((s) => TransferFormat[s]);
+            if (!requestedTransport || transport === requestedTransport) {
+                if (transferFormats.indexOf(requestedTransferFormat) >= 0) {
+                    this.logger.log(LogLevel.Trace, `Selecting transport '${transport}'`);
+                    return transport;
+                } else {
+                    this.logger.log(LogLevel.Trace, `Skipping transport '${transport}' because it does not support the requested transfer format '${requestedTransferFormat}'.`);
+                }
+            } else {
+                this.logger.log(LogLevel.Trace, `Skipping transport '${transport}' because it was disabled by the client.`);
+            }
+        }
+        return null;
     }
 
     private isITransport(transport: any): transport is ITransport {
@@ -151,7 +186,7 @@ export class HttpConnection implements IConnection {
 
     public send(data: any): Promise<void> {
         if (this.connectionState !== ConnectionState.Connected) {
-            throw new Error("Cannot send data if the connection is not in the 'Connected' State");
+            throw new Error("Cannot send data if the connection is not in the 'Connected' State.");
         }
 
         return this.transport.send(data);
@@ -210,7 +245,7 @@ export class HttpConnection implements IConnection {
         }
 
         const normalizedUrl = baseUrl + url;
-        this.logger.log(LogLevel.Information, `Normalizing '${url}' to '${normalizedUrl}'`);
+        this.logger.log(LogLevel.Information, `Normalizing '${url}' to '${normalizedUrl}'.`);
         return normalizedUrl;
     }
 

client-ts/signalr/src/HubConnection.ts

@@ -1,17 +1,16 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
-import { Base64EncodedHubProtocol } from "./Base64EncodedHubProtocol";
 import { ConnectionClosed } from "./Common";
 import { HttpConnection, IHttpConnectionOptions } from "./HttpConnection";
 import { IConnection } from "./IConnection";
-import { CancelInvocationMessage, CompletionMessage, HubMessage, IHubProtocol, InvocationMessage, MessageType, NegotiationMessage, ProtocolType, StreamInvocationMessage, StreamItemMessage } from "./IHubProtocol";
+import { CancelInvocationMessage, CompletionMessage, HubMessage, IHubProtocol, InvocationMessage, MessageType, NegotiationMessage, StreamInvocationMessage, StreamItemMessage } from "./IHubProtocol";
 import { ILogger, LogLevel } from "./ILogger";
 import { JsonHubProtocol } from "./JsonHubProtocol";
 import { ConsoleLogger, LoggerFactory, NullLogger } from "./Loggers";
 import { Observable, Subject } from "./Observable";
 import { TextMessageFormat } from "./TextMessageFormat";
-import { TransferMode, TransportType } from "./Transports";
+import { TransferFormat, TransportType } from "./Transports";
 
 export { JsonHubProtocol };
 
@@ -40,15 +39,16 @@ export class HubConnection {
 
         this.timeoutInMilliseconds = options.timeoutInMilliseconds || DEFAULT_TIMEOUT_IN_MS;
 
+        this.protocol = options.protocol || new JsonHubProtocol();
+
         if (typeof urlOrConnection === "string") {
-            this.connection = new HttpConnection(urlOrConnection, options);
+            this.connection = new HttpConnection(urlOrConnection, this.protocol.transferFormat, options);
         } else {
             this.connection = urlOrConnection;
         }
 
         this.logger = LoggerFactory.createLogger(options.logger);
 
-        this.protocol = options.protocol || new JsonHubProtocol();
         this.connection.onreceive = (data: any) => this.processIncomingData(data);
         this.connection.onclose = (error?: Error) => this.connectionClosed(error);
 
@@ -133,14 +133,7 @@ export class HubConnection {
     }
 
     public async start(): Promise<void> {
-        const requestedTransferMode =
-            (this.protocol.type === ProtocolType.Binary)
-                ? TransferMode.Binary
-                : TransferMode.Text;
-
-        this.connection.features.transferMode = requestedTransferMode;
         await this.connection.start();
-        const actualTransferMode = this.connection.features.transferMode;
 
         await this.connection.send(
             TextMessageFormat.write(
@@ -148,10 +141,6 @@ export class HubConnection {
 
         this.logger.log(LogLevel.Information, `Using HubProtocol '${this.protocol.name}'.`);
 
-        if (requestedTransferMode === TransferMode.Binary && actualTransferMode === TransferMode.Text) {
-            this.protocol = new Base64EncodedHubProtocol(this.protocol);
-        }
-
         this.configureTimeout();
     }
 

client-ts/signalr/src/IConnection.ts

@@ -2,7 +2,7 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 import { ConnectionClosed, DataReceived } from "./Common";
-import { ITransport, TransferMode, TransportType } from "./Transports";
+import { ITransport, TransportType } from "./Transports";
 
 export interface IConnection {
     readonly features: any;

client-ts/signalr/src/IHubProtocol.ts

@@ -1,4 +1,6 @@
-// Copyright (c) .NET Foundation. All rights reserved.
+import { TransferFormat } from "./Transports";
+
+// Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 export const enum MessageType {
@@ -58,14 +60,9 @@ export interface CancelInvocationMessage extends HubInvocationMessage {
     readonly type: MessageType.CancelInvocation;
 }
 
-export const enum ProtocolType {
-    Text = 1,
-    Binary,
-}
-
 export interface IHubProtocol {
     readonly name: string;
-    readonly type: ProtocolType;
+    readonly transferFormat: TransferFormat;
     parseMessages(input: any): HubMessage[];
     writeMessage(message: HubMessage): any;
 }

client-ts/signalr/src/JsonHubProtocol.ts

@@ -1,8 +1,9 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
-import { HubMessage, IHubProtocol, ProtocolType } from "./IHubProtocol";
+import { HubMessage, IHubProtocol } from "./IHubProtocol";
 import { TextMessageFormat } from "./TextMessageFormat";
+import { TransferFormat } from "./Transports";
 
 export const JSON_HUB_PROTOCOL_NAME: string = "json";
 
@@ -10,7 +11,7 @@ export class JsonHubProtocol implements IHubProtocol {
 
     public readonly name: string = JSON_HUB_PROTOCOL_NAME;
 
-    public readonly type: ProtocolType = ProtocolType.Text;
+    public readonly transferFormat: TransferFormat = TransferFormat.Text;
 
     public parseMessages(input: string): HubMessage[] {
         if (!input) {

client-ts/signalr/src/Transports.ts

@@ -7,6 +7,7 @@ import { HttpError, TimeoutError } from "./Errors";
 import { HttpClient, HttpRequest } from "./HttpClient";
 import { IConnection } from "./IConnection";
 import { ILogger, LogLevel } from "./ILogger";
+import { Arg } from "./Utils";
 
 export enum TransportType {
     WebSockets,
@@ -14,13 +15,13 @@ export enum TransportType {
     LongPolling,
 }
 
-export const enum TransferMode {
+export enum TransferFormat {
     Text = 1,
     Binary,
 }
 
 export interface ITransport {
-    connect(url: string, requestedTransferMode: TransferMode, connection: IConnection): Promise<TransferMode>;
+    connect(url: string, transferFormat: TransferFormat, connection: IConnection): Promise<void>;
     send(data: any): Promise<void>;
     stop(): Promise<void>;
     onreceive: DataReceived;
@@ -37,9 +38,17 @@ export class WebSocketTransport implements ITransport {
         this.accessTokenFactory = accessTokenFactory || (() => null);
     }
 
-    public connect(url: string, requestedTransferMode: TransferMode, connection: IConnection): Promise<TransferMode> {
+    public connect(url: string, transferFormat: TransferFormat, connection: IConnection): Promise<void> {
+        Arg.isRequired(url, "url");
+        Arg.isRequired(transferFormat, "transferFormat");
+        Arg.isIn(transferFormat, TransferFormat, "transferFormat");
+        Arg.isRequired(connection, "connection");
 
-        return new Promise<TransferMode>((resolve, reject) => {
+        if (typeof (WebSocket) === "undefined") {
+            throw new Error("'WebSocket' is not supported in your environment.");
+        }
+
+        return new Promise<void>((resolve, reject) => {
             url = url.replace(/^http/, "ws");
             const token = this.accessTokenFactory();
             if (token) {
@@ -47,18 +56,18 @@ export class WebSocketTransport implements ITransport {
             }
 
             const webSocket = new WebSocket(url);
-            if (requestedTransferMode === TransferMode.Binary) {
+            if (transferFormat === TransferFormat.Binary) {
                 webSocket.binaryType = "arraybuffer";
             }
 
             webSocket.onopen = (event: Event) => {
                 this.logger.log(LogLevel.Information, `WebSocket connected to ${url}`);
                 this.webSocket = webSocket;
-                resolve(requestedTransferMode);
+                resolve();
             };
 
-            webSocket.onerror = (event: Event) => {
+            webSocket.onerror = (event: ErrorEvent) => {
-                reject();
+                reject(event.error);
             };
 
             webSocket.onmessage = (message: MessageEvent) => {
@@ -115,13 +124,22 @@ export class ServerSentEventsTransport implements ITransport {
         this.logger = logger;
     }
 
-    public connect(url: string, requestedTransferMode: TransferMode, connection: IConnection): Promise<TransferMode> {
+    public connect(url: string, transferFormat: TransferFormat, connection: IConnection): Promise<void> {
+        Arg.isRequired(url, "url");
+        Arg.isRequired(transferFormat, "transferFormat");
+        Arg.isIn(transferFormat, TransferFormat, "transferFormat");
+        Arg.isRequired(connection, "connection");
+
         if (typeof (EventSource) === "undefined") {
-            Promise.reject("EventSource not supported by the browser.");
+            throw new Error("'EventSource' is not supported in your environment.");
         }
 
         this.url = url;
-        return new Promise<TransferMode>((resolve, reject) => {
+        return new Promise<void>((resolve, reject) => {
+            if (transferFormat !== TransferFormat.Text) {
+                reject(new Error("The Server-Sent Events transport only supports the 'Text' transfer format"));
+            }
+
             const token = this.accessTokenFactory();
             if (token) {
                 url += (url.indexOf("?") < 0 ? "?" : "&") + `access_token=${encodeURIComponent(token)}`;
@@ -145,7 +163,7 @@ export class ServerSentEventsTransport implements ITransport {
                 };
 
                 eventSource.onerror = (e: any) => {
-                    reject();
+                    reject(new Error(e.message || "Error occurred"));
 
                     // don't report an error if the transport did not start successfully
                     if (this.eventSource && this.onclose) {
@@ -157,7 +175,7 @@ export class ServerSentEventsTransport implements ITransport {
                     this.logger.log(LogLevel.Information, `SSE connected to ${this.url}`);
                     this.eventSource = eventSource;
                     // SSE is a text protocol
-                    resolve(TransferMode.Text);
+                    resolve();
                 };
             } catch (e) {
                 return Promise.reject(e);
@@ -197,29 +215,34 @@ export class LongPollingTransport implements ITransport {
         this.pollAbort = new AbortController();
     }
 
-    public connect(url: string, requestedTransferMode: TransferMode, connection: IConnection): Promise<TransferMode> {
+    public connect(url: string, transferFormat: TransferFormat, connection: IConnection): Promise<void> {
+        Arg.isRequired(url, "url");
+        Arg.isRequired(transferFormat, "transferFormat");
+        Arg.isIn(transferFormat, TransferFormat, "transferFormat");
+        Arg.isRequired(connection, "connection");
+
         this.url = url;
 
         // Set a flag indicating we have inherent keep-alive in this transport.
         connection.features.inherentKeepAlive = true;
 
-        if (requestedTransferMode === TransferMode.Binary && (typeof new XMLHttpRequest().responseType !== "string")) {
+        if (transferFormat === TransferFormat.Binary && (typeof new XMLHttpRequest().responseType !== "string")) {
             // This will work if we fix: https://github.com/aspnet/SignalR/issues/742
             throw new Error("Binary protocols over XmlHttpRequest not implementing advanced features are not supported.");
         }
 
-        this.poll(this.url, requestedTransferMode);
+        this.poll(this.url, transferFormat);
-        return Promise.resolve(requestedTransferMode);
+        return Promise.resolve();
     }
 
-    private async poll(url: string, transferMode: TransferMode): Promise<void> {
+    private async poll(url: string, transferFormat: TransferFormat): Promise<void> {
         const pollOptions: HttpRequest = {
             abortSignal: this.pollAbort.signal,
             headers: new Map<string, string>(),
             timeout: 90000,
         };
 
-        if (transferMode === TransferMode.Binary) {
+        if (transferFormat === TransferFormat.Binary) {
             pollOptions.responseType = "arraybuffer";
         }
 

client-ts/signalr/src/Utils.ts

@@ -0,0 +1,17 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+export class Arg {
+    public static isRequired(val: any, name: string): void {
+        if (val === null || val === undefined) {
+            throw new Error(`The '${name}' argument is required.`);
+        }
+    }
+
+    public static isIn(val: any, values: any, name: string): void {
+        // TypeScript enums have keys for **both** the name and the value of each enum member on the type itself.
+        if (!(val in values)) {
+            throw new Error(`Unknown ${name} value: ${val}.`);
+        }
+    }
+}

samples/ClientSample/RawSample.cs

@@ -1,4 +1,4 @@
-// Copyright (c) .NET Foundation. All rights reserved.
+// Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
@@ -8,6 +8,7 @@ using System.Net.Http;
 using System.Text;
 using System.Threading;
 using System.Threading.Tasks;
+using Microsoft.AspNetCore.Sockets;
 using Microsoft.AspNetCore.Sockets.Client;
 using Microsoft.Extensions.CommandLineUtils;
 using Microsoft.Extensions.Logging;
@@ -42,7 +43,7 @@ namespace ClientSample
                 var closeTcs = new TaskCompletionSource<object>();
                 connection.Closed += e => closeTcs.SetResult(null);
                 connection.OnReceived(data => Console.Out.WriteLineAsync($"{Encoding.UTF8.GetString(data)}"));
-                await connection.StartAsync();
+                await connection.StartAsync(TransferFormat.Text);
 
                 Console.WriteLine($"Connected to {baseUrl}");
                 var cts = new CancellationTokenSource();

samples/SocialWeather/PersistentConnectionLifeTimeManager.cs

@@ -29,10 +29,10 @@ namespace SocialWeather
             connection.Features.Get<IConnectionMetadataFeature>().Metadata["format"] = format;
             if (string.Equals(format, "protobuf", StringComparison.OrdinalIgnoreCase))
             {
-                var transferModeFeature = connection.Features.Get<ITransferModeFeature>();
+                var transferFormatFeature = connection.Features.Get<ITransferFormatFeature>();
-                if (transferModeFeature != null)
+                if (transferFormatFeature != null)
                 {
-                    transferModeFeature.TransferMode = TransferMode.Binary;
+                    transferFormatFeature.ActiveFormat = TransferFormat.Binary;
                 }
             }
             _connectionList.Add(connection);

samples/SocketsSample/Startup.cs

@@ -4,6 +4,7 @@
 using System;
 using Microsoft.AspNetCore.Builder;
 using Microsoft.AspNetCore.Hosting;
+using Microsoft.AspNetCore.Sockets;
 using Microsoft.Extensions.DependencyInjection;
 using MsgPack.Serialization;
 using SocketsSample.EndPoints;

samples/SocketsSample/web.config

@@ -1,14 +1,12 @@
 <?xml version="1.0" encoding="utf-8"?>
 <configuration>
-
   <!--
     Configure your application settings in appsettings.json. Learn more at http://go.microsoft.com/fwlink/?LinkId=786380
   -->
-
   <system.webServer>
     <handlers>
-      <add name="aspNetCore" path="*" verb="*" modules="AspNetCoreModule" resourceType="Unspecified"/>
+      <add name="aspNetCore" path="*" verb="*" modules="AspNetCoreModule" resourceType="Unspecified" />
     </handlers>
-    <aspNetCore processPath="%LAUNCHER_PATH%" arguments="%LAUNCHER_ARGS%" stdoutLogEnabled="false" stdoutLogFile=".\logs\stdout" forwardWindowsAuthToken="false"/>
+    <aspNetCore processPath="%LAUNCHER_PATH%" arguments="%LAUNCHER_ARGS%" stdoutLogEnabled="false" stdoutLogFile=".\logs\stdout" forwardWindowsAuthToken="false" startupTimeLimit="3600" requestTimeout="23:00:00" />
   </system.webServer>
-</configuration>
+</configuration>

samples/SocketsSample/wwwroot/hubs.html

@@ -15,7 +15,8 @@
         </select>
 
         <select id="transport">
-            <option value="WebSockets" selected>WebSockets</option>
+            <option value="Automatic" selected>Automatic</option>
+            <option value="WebSockets">WebSockets</option>
             <option value="ServerSentEvents">ServerSentEvents</option>
             <option value="LongPolling">LongPolling</option>
         </select>
@@ -135,14 +136,19 @@
     var connection;
 
     click('connect', function (event) {
-        let transportType = signalR.TransportType[transportDropdown.value] || signalR.TransportType.WebSockets;
         let hubRoute = hubTypeDropdown.value || "default";
         let protocol = protocolDropdown.value === "msgpack" ?
             new signalR.protocols.msgpack.MessagePackHubProtocol() :
             new signalR.JsonHubProtocol();
 
+        let options = { logger: logger, protocol: protocol };
+
+        if (transportDropdown.value !== "Automatic") {
+            options.transport = signalR.TransportType[transportDropdown.value];
+        }
+
         console.log('http://' + document.location.host + '/' + hubRoute);
-        connection = new signalR.HubConnection(hubRoute, { transport: transportType, logger: logger, protocol: protocol });
+        connection = new signalR.HubConnection(hubRoute, options);
         connection.on('Send', function (msg) {
             addLine('message-list', msg);
         });

specs/TransportProtocols.md

@@ -23,10 +23,34 @@ The `POST [endpoint-base]/negotiate` request is used to establish connection bet
 ```
 {
   "connectionId":"807809a5-31bf-470d-9e23-afaee35d8a0d",
-  "availableTransports":["WebSockets","ServerSentEvents","LongPolling"]
+  "availableTransports":[
+    {
+      "transport": "WebSockets",
+      "transferFormats": [ "Text", "Binary" ]
+    },
+    {
+      "transport": "ServerSentEvents",
+      "transferFormats": [ "Text" ]
+    },
+    {
+      "transport": "LongPolling",
+      "transferFormats": [ "Text", "Binary" ]
+    }
+  ]
 }
 ```
 
+The payload returned from this endpoint provides the following data:
+
+* The `connectionId` which is **required** by the Long Polling and Server-Sent Events transports (in order to correlate sends and receives).
+* The `availableTransports` list which describes the transports the server supports. For each transport, the name of the transport (`transport`) is listed, as is a list of "transfer formats" supported by the transport (`transferFormats`)
+
+## Transfer Formats
+
+ASP.NET Endpoints support two different transfer formats: `Text` and `Binary`. `Text` refers to UTF-8 text, and `Binary` refers to any arbitrary binary data. The transfer format serves two purposes. First, in the WebSockets transport, it is used to determine if `Text` or `Binary` WebSocket frames should be used to carry data. This is useful in debugging as most browser Dev Tools only show the content of `Text` frames. When using a text-based protocol like JSON, it is preferable for the WebSockets transport to use `Text` frames. How a client/server indicate the transfer format currently being used is implementation-defined.
+
+Some transports are limited to supporting only `Text` data (specifically, Server-Sent Events). These transports cannot carry arbitrary binary data (without additional encoding, such as Base-64) due to limitations in their protocol. The transfer formats supported by each transport are described as part of the `POST [endpoint-base]/negotiate` response to allow clients to ignore transports that cannot support arbitrary binary data when they have a need to send/receive that data. How the client indicates the transfer format it wishes to use is also implementation-defined.
+
 ## WebSockets (Full Duplex)
 
 The WebSockets transport is unique in that it is full duplex, and a persistent connection that can be established in a single operation. As a result, the client is not required to use the `POST [endpoint-base]/negotiate` request to establish a connection in advance. It also includes all the necessary metadata in it's own frame metadata.
@@ -53,7 +77,6 @@ If the relevant connection has been terminated, a `404 Not Found` status code is
 
 Server-Sent Events (SSE) is a protocol specified by WHATWG at [https://html.spec.whatwg.org/multipage/comms.html#server-sent-events](https://html.spec.whatwg.org/multipage/comms.html#server-sent-events). It is capable of sending data from server to client only, so it must be paired with the HTTP Post transport. It also requires a connection already be established using the `POST [endpoint-base]/negotiate` request.
 
-
 The protocol is similar to Long Polling in that the client opens a request to an endpoint and leaves it open. The server transmits frames as "events" using the SSE protocol. The protocol encodes a single event as a sequence of key-value pair lines, separated by `:` and using any of `\r\n`, `\n` or `\r` as line-terminators, followed by a final blank line. Keys can be duplicated and their values are concatenated with `\n`. So the following represents two events:
 
 ```
@@ -71,6 +94,8 @@ In the first event, the value of `baz` would be `boz\nbiz\nflarg`, due to the co
 
 In this transport, the client establishes an SSE connection to `[endpoint-base]` with an `Accept` header of `text/event-stream`, and the server responds with an HTTP response with a `Content-Type` of `text/event-stream`. The **mandatory** `connectionId` query string value is used to identify the connection to send to. If there is no `connectionId` query string value, a `400 Bad Request` response is returned, if there is no connection with the specified ID, a `404 Not Found` response is returned. Each SSE event represents a single frame from client to server. The transport uses unnamed events, which means only the `data` field is available. Thus we use the first line of the `data` field for frame metadata.
 
+The Server-Sent Events transport only supports text data, because it is a text-based protocol. As a result, it is reported by the server as supporting only the `Text` transfer format. If a client wishes to send arbitrary binary data, it should skip the Server-Sent Events transport when selecting an appropriate transport.
+
 ## Long Polling (Server-to-Client only)
 
 Long Polling is a server-to-client half-transport, so it is always paired with HTTP Post. It requires a connection already be established using the `POST [endpoint-base]/negotiate` request.

src/Microsoft.AspNetCore.SignalR.Client.Core/HubConnection.Log.cs

@@ -1,4 +1,4 @@
-// Copyright (c) .NET Foundation. All rights reserved.
+// Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;

src/Microsoft.AspNetCore.SignalR.Client.Core/HubConnection.cs

@@ -4,13 +4,11 @@
 using System;
 using System.Collections.Concurrent;
 using System.Collections.Generic;
-using System.Diagnostics;
 using System.IO;
 using System.Threading;
-using System.Threading.Tasks;
 using System.Threading.Channels;
+using System.Threading.Tasks;
 using Microsoft.AspNetCore.SignalR.Internal;
-using Microsoft.AspNetCore.SignalR.Internal.Encoders;
 using Microsoft.AspNetCore.SignalR.Internal.Protocol;
 using Microsoft.AspNetCore.Sockets;
 using Microsoft.AspNetCore.Sockets.Client;
@@ -30,7 +28,6 @@ namespace Microsoft.AspNetCore.SignalR.Client
         private readonly IConnection _connection;
         private readonly IHubProtocol _protocol;
         private readonly HubBinder _binder;
-        private HubProtocolReaderWriter _protocolReaderWriter;
 
         private readonly object _pendingCallsLock = new object();
         private readonly Dictionary<string, InvocationRequest> _pendingCalls = new Dictionary<string, InvocationRequest>();
@@ -113,26 +110,9 @@ namespace Microsoft.AspNetCore.SignalR.Client
 
         private async Task StartAsyncCore()
         {
-            var transferModeFeature = _connection.Features.Get<ITransferModeFeature>();
+            await _connection.StartAsync(_protocol.TransferFormat);
-            if (transferModeFeature == null)
-            {
-                transferModeFeature = new TransferModeFeature();
-                _connection.Features.Set(transferModeFeature);
-            }
-
-            var requestedTransferMode =
-                _protocol.Type == ProtocolType.Binary
-                    ? TransferMode.Binary
-                    : TransferMode.Text;
-
-            transferModeFeature.TransferMode = requestedTransferMode;
-            await _connection.StartAsync();
             _needKeepAlive = _connection.Features.Get<IConnectionInherentKeepAliveFeature>() == null;
 
-            var actualTransferMode = transferModeFeature.TransferMode;
-
-            _protocolReaderWriter = new HubProtocolReaderWriter(_protocol, GetDataEncoder(requestedTransferMode, actualTransferMode));
-
             Log.HubProtocol(_logger, _protocol.Name);
 
             _connectionActive = new CancellationTokenSource();
@@ -146,20 +126,6 @@ namespace Microsoft.AspNetCore.SignalR.Client
             ResetTimeoutTimer();
         }
 
-        private IDataEncoder GetDataEncoder(TransferMode requestedTransferMode, TransferMode actualTransferMode)
-        {
-            if (requestedTransferMode == TransferMode.Binary && actualTransferMode == TransferMode.Text)
-            {
-                // This is for instance for SSE which is a Text protocol and the user wants to use a binary
-                // protocol so we need to encode messages.
-                return new Base64Encoder();
-            }
-
-            Debug.Assert(requestedTransferMode == actualTransferMode, "All transports besides SSE are expected to support binary mode.");
-
-            return new PassThroughEncoder();
-        }
-
         public async Task StopAsync() => await StopAsyncCore().ForceAsync();
 
         private Task StopAsyncCore() => _connection.StopAsync();
@@ -295,7 +261,7 @@ namespace Microsoft.AspNetCore.SignalR.Client
         {
             try
             {
-                var payload = _protocolReaderWriter.WriteMessage(hubMessage);
+                var payload = _protocol.WriteToArray(hubMessage);
                 Log.SendInvocation(_logger, hubMessage.InvocationId);
 
                 await _connection.SendAsync(payload, irq.CancellationToken);
@@ -328,7 +294,7 @@ namespace Microsoft.AspNetCore.SignalR.Client
             {
                 Log.PreparingNonBlockingInvocation(_logger, methodName, args.Length);
 
-                var payload = _protocolReaderWriter.WriteMessage(invocationMessage);
+                var payload = _protocol.WriteToArray(invocationMessage);
                 Log.SendInvocation(_logger, invocationMessage.InvocationId);
 
                 await _connection.SendAsync(payload, cancellationToken);
@@ -345,7 +311,8 @@ namespace Microsoft.AspNetCore.SignalR.Client
         {
             ResetTimeoutTimer();
             Log.ParsingMessages(_logger, data.Length);
-            if (_protocolReaderWriter.ReadMessages(data, _binder, out var messages))
+            var messages = new List<HubMessage>();
+            if (_protocol.TryParseMessages(data, _binder, messages))
             {
                 Log.ReceivingMessages(_logger, messages.Count);
                 foreach (var message in messages)
@@ -621,10 +588,5 @@ namespace Microsoft.AspNetCore.SignalR.Client
                 return _callback(parameters, _state);
             }
         }
-
-        private class TransferModeFeature : ITransferModeFeature
-        {
-            public TransferMode TransferMode { get; set; }
-        }
     }
 }

src/Microsoft.AspNetCore.SignalR.Common/Internal/Encoders/Base64Encoder.cs

@@ -1,59 +0,0 @@
-// Copyright (c) .NET Foundation. All rights reserved.
-// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
-
-using System;
-using System.Buffers;
-using System.Buffers.Text;
-using System.Diagnostics;
-
-namespace Microsoft.AspNetCore.SignalR.Internal.Encoders
-{
-    public class Base64Encoder : IDataEncoder
-    {
-        public bool TryDecode(ref ReadOnlySpan<byte> buffer, out ReadOnlySpan<byte> data)
-        {
-            if (LengthPrefixedTextMessageParser.TryParseMessage(ref buffer, out var message))
-            {
-                Span<byte> decoded = new byte[Base64.GetMaxDecodedFromUtf8Length(message.Length)];
-                var status = Base64.DecodeFromUtf8(message, decoded, out _, out var written);
-                Debug.Assert(status == OperationStatus.Done);
-                data = decoded.Slice(0, written);
-                return true;
-            }
-            return false;
-        }
-
-        private const int Int32OverflowLength = 10;
-
-        public byte[] Encode(byte[] payload)
-        {
-            var maxEncodedLength = Base64.GetMaxEncodedToUtf8Length(payload.Length);
-
-            // Int32OverflowLength + length of separator (':') + length of terminator (';')
-            if (int.MaxValue - maxEncodedLength < Int32OverflowLength + 2)
-            {
-                throw new FormatException("The encoded message exceeds the maximum supported size.");
-            }
-
-            //The format is: [{length}:{message};] so allocate enough to be able to write the entire message
-            Span<byte> buffer = new byte[Int32OverflowLength + 1 + maxEncodedLength + 1];
-
-            buffer[Int32OverflowLength] = (byte)':';
-            var status = Base64.EncodeToUtf8(payload, buffer.Slice(Int32OverflowLength + 1), out _, out var written);
-            Debug.Assert(status == OperationStatus.Done);
-
-            buffer[Int32OverflowLength + 1 + written] = (byte)';';
-            var prefixLength = 0;
-            var prefix = written;
-            do
-            {
-                buffer[Int32OverflowLength - 1 - prefixLength] = (byte)('0' + prefix % 10);
-                prefix /= 10;
-                prefixLength++;
-            }
-            while (prefix > 0);
-
-            return buffer.Slice(Int32OverflowLength - prefixLength, prefixLength + 1 + written + 1).ToArray();
-        }
-    }
-}

src/Microsoft.AspNetCore.SignalR.Common/Internal/Encoders/IDataEncoder.cs

@@ -1,13 +0,0 @@
-// Copyright (c) .NET Foundation. All rights reserved.
-// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
-
-using System;
-
-namespace Microsoft.AspNetCore.SignalR.Internal.Encoders
-{
-    public interface IDataEncoder
-    {
-        byte[] Encode(byte[] payload);
-        bool TryDecode(ref ReadOnlySpan<byte> buffer, out ReadOnlySpan<byte> data);
-    }
-}

src/Microsoft.AspNetCore.SignalR.Common/Internal/Encoders/LengthPrefixedTextMessageParser.cs

@@ -1,94 +0,0 @@
-// Copyright (c) .NET Foundation. All rights reserved.
-// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
-
-using System;
-using System.Buffers.Text;
-using System.Text;
-
-namespace Microsoft.AspNetCore.SignalR.Internal.Encoders
-{
-    public static class LengthPrefixedTextMessageParser
-    {
-        private const char FieldDelimiter = ':';
-        private const char MessageDelimiter = ';';
-
-        /// <summary>
-        /// Attempts to parse a message from the buffer. Returns 'false' if there is not enough data to complete a message. Throws an
-        /// exception if there is a format error in the provided data.
-        /// </summary>
-        public static bool TryParseMessage(ref ReadOnlySpan<byte> buffer, out ReadOnlySpan<byte> payload)
-        {
-            payload = default;
-
-            if (!TryReadLength(buffer, out var index, out var length))
-            {
-                return false;
-            }
-
-            var remaining = buffer.Slice(index);
-
-            if (!TryReadDelimiter(remaining, FieldDelimiter, "length"))
-            {
-                return false;
-            }
-
-            // Skip the delimeter
-            remaining = remaining.Slice(1);
-
-            if (remaining.Length < length + 1)
-            {
-                return false;
-            }
-
-            payload = remaining.Slice(0, length);
-
-            remaining = remaining.Slice(length);
-
-            if (!TryReadDelimiter(remaining, MessageDelimiter, "payload"))
-            {
-                return false;
-            }
-
-            // Skip the delimeter
-            buffer = remaining.Slice(1);
-            return true;
-        }
-
-        private static bool TryReadLength(ReadOnlySpan<byte> buffer, out int index, out int length)
-        {
-            length = 0;
-            // Read until the first ':' to find the length
-            index = buffer.IndexOf((byte)FieldDelimiter);
-
-            if (index == -1)
-            {
-                // Insufficient data
-                return false;
-            }
-
-            var lengthSpan = buffer.Slice(0, index);
-
-            if (!Utf8Parser.TryParse(buffer, out length, out var bytesConsumed) || bytesConsumed < lengthSpan.Length)
-            {
-                throw new FormatException($"Invalid length: '{Encoding.UTF8.GetString(lengthSpan.ToArray())}'");
-            }
-
-            return true;
-        }
-
-        private static bool TryReadDelimiter(ReadOnlySpan<byte> buffer, char delimiter, string field)
-        {
-            if (buffer.Length == 0)
-            {
-                return false;
-            }
-
-            if (buffer[0] != delimiter)
-            {
-                throw new FormatException($"Missing delimiter '{delimiter}' after {field}");
-            }
-
-            return true;
-        }
-    }
-}

src/Microsoft.AspNetCore.SignalR.Common/Internal/Encoders/PassThroughEncoder.cs

@@ -1,22 +0,0 @@
-// Copyright (c) .NET Foundation. All rights reserved.
-// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
-
-using System;
-
-namespace Microsoft.AspNetCore.SignalR.Internal.Encoders
-{
-    public class PassThroughEncoder : IDataEncoder
-    {
-        public bool TryDecode(ref ReadOnlySpan<byte> buffer, out ReadOnlySpan<byte> data)
-        {
-            data = buffer;
-            buffer = Array.Empty<byte>();
-            return true;
-        }
-
-        public byte[] Encode(byte[] payload)
-        {
-            return payload;
-        }
-    }
-}

src/Microsoft.AspNetCore.SignalR.Common/Internal/HubProtocolReaderWriter.cs

@@ -1,74 +0,0 @@
-// Copyright (c) .NET Foundation. All rights reserved.
-// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
-
-using System;
-using System.Buffers;
-using System.Collections;
-using System.Collections.Generic;
-using System.IO;
-using Microsoft.AspNetCore.SignalR.Internal.Encoders;
-using Microsoft.AspNetCore.SignalR.Internal.Protocol;
-
-namespace Microsoft.AspNetCore.SignalR.Internal
-{
-    public class HubProtocolReaderWriter
-    {
-        private readonly IHubProtocol _hubProtocol;
-        private readonly IDataEncoder _dataEncoder;
-
-        public HubProtocolReaderWriter(IHubProtocol hubProtocol, IDataEncoder dataEncoder)
-        {
-            _hubProtocol = hubProtocol;
-            _dataEncoder = dataEncoder;
-        }
-
-        public bool ReadMessages(ReadOnlySequence<byte> buffer, IInvocationBinder binder, out IList<HubMessage> messages, out SequencePosition consumed, out SequencePosition examined)
-        {
-            // TODO: Fix this implementation to be incremental
-            consumed = buffer.End;
-            examined = consumed;
-
-            return ReadMessages(buffer.ToArray(), binder, out messages);
-        }
-
-        public bool ReadMessages(byte[] input, IInvocationBinder binder, out IList<HubMessage> messages)
-        {
-            messages = new List<HubMessage>();
-            ReadOnlySpan<byte> span = input;
-            while (span.Length > 0 && _dataEncoder.TryDecode(ref span, out var data))
-            {
-                _hubProtocol.TryParseMessages(data, binder, messages);
-            }
-            return messages.Count > 0;
-        }
-
-        public byte[] WriteMessage(HubMessage hubMessage)
-        {
-            using (var ms = new MemoryStream())
-            {
-                _hubProtocol.WriteMessage(hubMessage, ms);
-                return _dataEncoder.Encode(ms.ToArray());
-            }
-        }
-
-        public override bool Equals(object obj)
-        {
-            var readerWriter = obj as HubProtocolReaderWriter;
-            if (readerWriter == null)
-            {
-                return false;
-            }
-
-            // Note: ReferenceEquals on HubProtocol works for our implementation of IHubProtocolResolver because we use Singletons from DI
-            // However if someone replaces the implementation and returns a new ProtocolResolver for every connection they wont get the perf benefits
-            // Memory growth is mitigated by capping the cache size
-            return ReferenceEquals(_dataEncoder, readerWriter._dataEncoder) && ReferenceEquals(_hubProtocol, readerWriter._hubProtocol);
-        }
-
-        // This should never be used, needed because you can't override Equals without it
-        public override int GetHashCode()
-        {
-            return base.GetHashCode();
-        }
-    }
-}

src/Microsoft.AspNetCore.SignalR.Common/Internal/Protocol/HubMessage.cs

@@ -2,6 +2,7 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System.Collections.Generic;
+using System.IO;
 
 namespace Microsoft.AspNetCore.SignalR.Internal.Protocol
 {
@@ -11,39 +12,48 @@ namespace Microsoft.AspNetCore.SignalR.Internal.Protocol
         {
         }
 
-        // Initialize with capacity 4 for the 2 built in protocols and 2 data encoders
+        // Initialize with capacity 2 for the 2 built in protocols
-        private readonly List<SerializedMessage> _serializedMessages = new List<SerializedMessage>(4);
+        private object _lock = new object();
+        private readonly List<SerializedMessage> _serializedMessages = new List<SerializedMessage>(2);
 
-        public byte[] WriteMessage(HubProtocolReaderWriter protocolReaderWriter)
+        public byte[] WriteMessage(IHubProtocol protocol)
         {
-            for (var i = 0; i < _serializedMessages.Count; i++)
+            // REVIEW: Revisit lock
+            // Could use a reader/writer lock to allow the loop to take place in "unlocked" code
+            // Or, could use a fixed size array and Interlocked to manage it.
+            // Or, Immutable *ducks*
+
+            lock (_lock)
             {
-                if (_serializedMessages[i].ProtocolReaderWriter.Equals(protocolReaderWriter))
+                for (var i = 0; i < _serializedMessages.Count; i++)
                 {
-                    return _serializedMessages[i].Message;
+                    if (_serializedMessages[i].Protocol.Equals(protocol))
+                    {
+                        return _serializedMessages[i].Message;
+                    }
                 }
+
+                var bytes = protocol.WriteToArray(this);
+
+                // We don't want to balloon memory if someone writes a poor IHubProtocolResolver
+                // So we cap how many caches we store and worst case just serialize the message for every connection
+                if (_serializedMessages.Count < 10)
+                {
+                    _serializedMessages.Add(new SerializedMessage(protocol, bytes));
+                }
+
+                return bytes;
             }
-
-            var bytes = protocolReaderWriter.WriteMessage(this);
-
-            // We don't want to balloon memory if someone writes a poor IHubProtocolResolver
-            // So we cap how many caches we store and worst case just serialize the message for every connection
-            if (_serializedMessages.Count < 10)
-            {
-                _serializedMessages.Add(new SerializedMessage(protocolReaderWriter, bytes));
-            }
-
-            return bytes;
         }
 
         private readonly struct SerializedMessage
         {
-            public readonly HubProtocolReaderWriter ProtocolReaderWriter;
+            public readonly IHubProtocol Protocol;
             public readonly byte[] Message;
 
-            public SerializedMessage(HubProtocolReaderWriter protocolReaderWriter, byte[] message)
+            public SerializedMessage(IHubProtocol protocol, byte[] message)
             {
-                ProtocolReaderWriter = protocolReaderWriter;
+                Protocol = protocol;
                 Message = message;
             }
         }

src/Microsoft.AspNetCore.SignalR.Common/Internal/Protocol/HubProtocolExtensions.cs

@@ -0,0 +1,19 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System.IO;
+
+namespace Microsoft.AspNetCore.SignalR.Internal.Protocol
+{
+    public static class HubProtocolExtensions
+    {
+        public static byte[] WriteToArray(this IHubProtocol hubProtocol, HubMessage message)
+        {
+            using (var ms = new MemoryStream())
+            {
+                hubProtocol.WriteMessage(message, ms);
+                return ms.ToArray();
+            }
+        }
+    }
+}

src/Microsoft.AspNetCore.SignalR.Common/Internal/Protocol/IHubProtocol.cs

@@ -4,6 +4,7 @@
 using System;
 using System.Collections.Generic;
 using System.IO;
+using Microsoft.AspNetCore.Sockets;
 
 namespace Microsoft.AspNetCore.SignalR.Internal.Protocol
 {
@@ -11,7 +12,7 @@ namespace Microsoft.AspNetCore.SignalR.Internal.Protocol
     {
         string Name { get; }
 
-        ProtocolType Type { get; }
+        TransferFormat TransferFormat { get; }
 
         bool TryParseMessages(ReadOnlySpan<byte> input, IInvocationBinder binder, IList<HubMessage> messages);
 

src/Microsoft.AspNetCore.SignalR.Common/Internal/Protocol/JsonHubProtocol.cs

@@ -7,6 +7,7 @@ using System.IO;
 using System.Runtime.ExceptionServices;
 using System.Text;
 using Microsoft.AspNetCore.SignalR.Internal.Formatters;
+using Microsoft.AspNetCore.Sockets;
 using Microsoft.Extensions.Options;
 using Newtonsoft.Json;
 using Newtonsoft.Json.Linq;
@@ -44,7 +45,7 @@ namespace Microsoft.AspNetCore.SignalR.Internal.Protocol
 
         public string Name => ProtocolName;
 
-        public ProtocolType Type => ProtocolType.Text;
+        public TransferFormat TransferFormat => TransferFormat.Text;
 
         public bool TryParseMessages(ReadOnlySpan<byte> input, IInvocationBinder binder, IList<HubMessage> messages)
         {

src/Microsoft.AspNetCore.SignalR.Common/Internal/Protocol/ProtocolType.cs

@@ -1,11 +0,0 @@
-// Copyright (c) .NET Foundation. All rights reserved.
-// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
-
-namespace Microsoft.AspNetCore.SignalR.Internal.Protocol
-{
-    public enum ProtocolType
-    {
-        Binary,
-        Text
-    }
-}

src/Microsoft.AspNetCore.SignalR.Common/Microsoft.AspNetCore.SignalR.Common.csproj

@@ -15,4 +15,8 @@
     <PackageReference Include="Microsoft.Extensions.Options" Version="$(MicrosoftExtensionsOptionsPackageVersion)" />
   </ItemGroup>
 
+  <ItemGroup>
+    <ProjectReference Include="..\Microsoft.AspNetCore.Sockets.Abstractions\Microsoft.AspNetCore.Sockets.Abstractions.csproj" />
+  </ItemGroup>
+
 </Project>

src/Microsoft.AspNetCore.SignalR.Core/HubConnectionContext.cs

@@ -16,9 +16,7 @@ using Microsoft.AspNetCore.Http.Features;
 using Microsoft.AspNetCore.Protocols;
 using Microsoft.AspNetCore.SignalR.Core;
 using Microsoft.AspNetCore.SignalR.Internal;
-using Microsoft.AspNetCore.SignalR.Internal.Encoders;
 using Microsoft.AspNetCore.SignalR.Internal.Protocol;
-using Microsoft.AspNetCore.Sockets;
 using Microsoft.AspNetCore.Sockets.Features;
 using Microsoft.Extensions.Logging;
 
@@ -27,8 +25,6 @@ namespace Microsoft.AspNetCore.SignalR
     public class HubConnectionContext
     {
         private static Action<object> _abortedCallback = AbortConnection;
-        private static readonly Base64Encoder Base64Encoder = new Base64Encoder();
-        private static readonly PassThroughEncoder PassThroughEncoder = new PassThroughEncoder();
 
         private readonly ConnectionContext _connectionContext;
         private readonly ILogger _logger;
@@ -62,7 +58,7 @@ namespace Microsoft.AspNetCore.SignalR
 
         public string UserIdentifier { get; private set; }
 
-        internal virtual HubProtocolReaderWriter ProtocolReaderWriter { get; set; }
+        internal virtual IHubProtocol Protocol { get; set; }
 
         internal ExceptionDispatchInfo AbortException { get; private set; }
 
@@ -85,7 +81,7 @@ namespace Microsoft.AspNetCore.SignalR
             {
                 // This will internally cache the buffer for each unique HubProtocol/DataEncoder combination
                 // So that we don't serialize the HubMessage for every single connection
-                var buffer = message.WriteMessage(ProtocolReaderWriter);
+                var buffer = message.WriteMessage(Protocol);
                 _connectionContext.Transport.Output.Write(buffer);
 
                 Interlocked.Exchange(ref _lastSendTimestamp, Stopwatch.GetTimestamp());
@@ -156,27 +152,25 @@ namespace Microsoft.AspNetCore.SignalR
                             {
                                 if (NegotiationProtocol.TryParseMessage(buffer, out var negotiationMessage, out consumed, out examined))
                                 {
-                                    var protocol = protocolResolver.GetProtocol(negotiationMessage.Protocol, supportedProtocols, this);
+                                    Protocol = protocolResolver.GetProtocol(negotiationMessage.Protocol, supportedProtocols, this);
 
-                                    var transportCapabilities = Features.Get<IConnectionTransportFeature>()?.TransportCapabilities
+                                    // If there's a transfer format feature, we need to check if we're compatible and set the active format.
-                                        ?? throw new InvalidOperationException("Unable to read transport capabilities.");
+                                    // If there isn't a feature, it means that the transport supports binary data and doesn't need us to tell them
+                                    // what format we're writing.
+                                    var transferFormatFeature = Features.Get<ITransferFormatFeature>();
+                                    if (transferFormatFeature != null)
+                                    {
+                                        if ((transferFormatFeature.SupportedFormats & Protocol.TransferFormat) == 0)
+                                        {
+                                            throw new InvalidOperationException($"Cannot use the '{Protocol.Name}' protocol on the current transport. The transport does not support the '{Protocol.TransferFormat}' transfer mode.");
+                                        }
 
-                                    var dataEncoder = (protocol.Type == ProtocolType.Binary && (transportCapabilities & TransferMode.Binary) == 0)
+                                        transferFormatFeature.ActiveFormat = Protocol.TransferFormat;
-                                        ? (IDataEncoder)Base64Encoder
+                                    }
-                                        : PassThroughEncoder;
 
-                                    var transferModeFeature = Features.Get<ITransferModeFeature>() ??
+                                    _cachedPingMessage = Protocol.WriteToArray(PingMessage.Instance);
-                                        throw new InvalidOperationException("Unable to read transfer mode.");
 
-                                    transferModeFeature.TransferMode =
+                                    Log.UsingHubProtocol(_logger, Protocol.Name);
-                                        (protocol.Type == ProtocolType.Binary && (transportCapabilities & TransferMode.Binary) != 0)
-                                            ? TransferMode.Binary
-                                            : TransferMode.Text;
-
-                                    ProtocolReaderWriter = new HubProtocolReaderWriter(protocol, dataEncoder);
-                                    _cachedPingMessage = ProtocolReaderWriter.WriteMessage(PingMessage.Instance);
-
-                                    Log.UsingHubProtocol(_logger, protocol.Name);
 
                                     UserIdentifier = userIdProvider.GetUserId(this);
 

src/Microsoft.AspNetCore.SignalR.Core/HubEndPoint.cs

@@ -2,10 +2,13 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
+using System.Buffers;
+using System.Collections.Generic;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Protocols;
 using Microsoft.AspNetCore.SignalR.Core;
 using Microsoft.AspNetCore.SignalR.Internal;
+using Microsoft.AspNetCore.SignalR.Internal.Protocol;
 using Microsoft.Extensions.Logging;
 using Microsoft.Extensions.Options;
 
@@ -141,7 +144,10 @@ namespace Microsoft.AspNetCore.SignalR
                     {
                         if (!buffer.IsEmpty)
                         {
-                            if (connection.ProtocolReaderWriter.ReadMessages(buffer, _dispatcher, out var hubMessages, out consumed, out examined))
+                            var hubMessages = new List<HubMessage>();
+
+                            // TODO: Make this incremental
+                            if (connection.Protocol.TryParseMessages(buffer.ToArray(), _dispatcher, hubMessages))
                             {
                                 foreach (var hubMessage in hubMessages)
                                 {

src/Microsoft.AspNetCore.SignalR.Protocols.MsgPack/Internal/Protocol/MessagePackHubProtocol.cs

@@ -6,6 +6,7 @@ using System.Collections.Generic;
 using System.IO;
 using System.Runtime.ExceptionServices;
 using Microsoft.AspNetCore.SignalR.Internal.Formatters;
+using Microsoft.AspNetCore.Sockets;
 using Microsoft.Extensions.Options;
 using MsgPack;
 using MsgPack.Serialization;
@@ -24,7 +25,7 @@ namespace Microsoft.AspNetCore.SignalR.Internal.Protocol
 
         public string Name => ProtocolName;
 
-        public ProtocolType Type => ProtocolType.Binary;
+        public TransferFormat TransferFormat => TransferFormat.Binary;
 
         public MessagePackHubProtocol()
             : this(Options.Create(new MessagePackHubProtocolOptions()))

src/Microsoft.AspNetCore.Sockets.Abstractions/Features/IConnectionTransportFeature.cs

@@ -1,4 +1,4 @@
-// Copyright (c) .NET Foundation. All rights reserved.
+// Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System.IO.Pipelines;
@@ -8,7 +8,5 @@ namespace Microsoft.AspNetCore.Sockets.Features
     public interface IConnectionTransportFeature
     {
         IDuplexPipe Transport { get; set; }
-
-        TransferMode TransportCapabilities { get; set; }
     }
 }

src/Microsoft.AspNetCore.Sockets.Abstractions/Features/ITransferFormatFeature.cs

@@ -0,0 +1,11 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+namespace Microsoft.AspNetCore.Sockets.Features
+{
+    public interface ITransferFormatFeature
+    {
+        TransferFormat SupportedFormats { get; }
+        TransferFormat ActiveFormat { get; set; }
+    }
+}

src/Microsoft.AspNetCore.Sockets.Abstractions/Features/ITransferModeFeature.cs

@@ -1,10 +0,0 @@
-// Copyright (c) .NET Foundation. All rights reserved.
-// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
-
-namespace Microsoft.AspNetCore.Sockets.Features
-{
-    public interface ITransferModeFeature
-    {
-        TransferMode TransferMode { get; set; }
-    }
-}

src/Microsoft.AspNetCore.Sockets.Abstractions/IConnection.cs

@@ -10,7 +10,7 @@ namespace Microsoft.AspNetCore.Sockets.Client
 {
     public interface IConnection
     {
-        Task StartAsync();
+        Task StartAsync(TransferFormat transferFormat);
         Task SendAsync(byte[] data, CancellationToken cancellationToken);
         Task StopAsync();
         Task DisposeAsync();

src/Microsoft.AspNetCore.Sockets.Abstractions/TransferFormat.cs

@@ -1,4 +1,4 @@
-// Copyright (c) .NET Foundation. All rights reserved.
+// Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
@@ -6,7 +6,7 @@ using System;
 namespace Microsoft.AspNetCore.Sockets
 {
     [Flags]
-    public enum TransferMode
+    public enum TransferFormat
     {
         Binary = 0x01,
         Text = 0x02

src/Microsoft.AspNetCore.Sockets.Client.Http/HttpConnection.Log.cs

@@ -1,4 +1,4 @@
-// Copyright (c) .NET Foundation. All rights reserved.
+// Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
@@ -85,6 +85,18 @@ namespace Microsoft.AspNetCore.Sockets.Client
             private static readonly Action<ILogger, string, string, Exception> _connectionStateChanged =
                 LoggerMessage.Define<string, string>(LogLevel.Debug, new EventId(25, "ConnectionStateChanged"), "Connection state changed from {previousState} to {newState}.");
 
+            private static readonly Action<ILogger, string, Exception> _transportNotSupported =
+                LoggerMessage.Define<string>(LogLevel.Debug, new EventId(26, "TransportNotSupported"), "Skipping transport {transportName} because it is not supported by this client.");
+
+            private static readonly Action<ILogger, string, string, Exception> _transportDoesNotSupportTransferFormat =
+                LoggerMessage.Define<string, string>(LogLevel.Debug, new EventId(27, "TransportDoesNotSupportTransferFormat"), "Skipping transport {transportName} because it does not support the requested transfer format '{transferFormat}'.");
+
+            private static readonly Action<ILogger, string, Exception> _transportDisabledByClient =
+                LoggerMessage.Define<string>(LogLevel.Debug, new EventId(28, "TransportDisabledByClient"), "Skipping transport {transportName} because it was disabled by the client.");
+
+            private static readonly Action<ILogger, string, Exception> _transportFailed =
+                LoggerMessage.Define<string>(LogLevel.Debug, new EventId(29, "TransportFailed"), "Skipping transport {transportName} because it failed to initialize.");
+
             public static void HttpConnectionStarting(ILogger logger)
             {
                 _httpConnectionStarting(logger, null);
@@ -218,6 +230,35 @@ namespace Microsoft.AspNetCore.Sockets.Client
             {
                 _errorDuringClosedEvent(logger, exception);
             }
+
+            public static void TransportNotSupported(ILogger logger, string transport)
+            {
+                _transportNotSupported(logger, transport, null);
+            }
+
+            public static void TransportDoesNotSupportTransferFormat(ILogger logger, TransportType transport, TransferFormat transferFormat)
+            {
+                if (logger.IsEnabled(LogLevel.Debug))
+                {
+                    _transportDoesNotSupportTransferFormat(logger, transport.ToString(), transferFormat.ToString(), null);
+                }
+            }
+
+            public static void TransportDisabledByClient(ILogger logger, TransportType transport)
+            {
+                if (logger.IsEnabled(LogLevel.Debug))
+                {
+                    _transportDisabledByClient(logger, transport.ToString(), null);
+                }
+            }
+
+            public static void TransportFailed(ILogger logger, TransportType transport, Exception ex)
+            {
+                if (logger.IsEnabled(LogLevel.Debug))
+                {
+                    _transportFailed(logger, transport.ToString(), ex);
+                }
+            }
         }
     }
 }

src/Microsoft.AspNetCore.Sockets.Client.Http/HttpConnection.cs

@@ -6,13 +6,13 @@ using System.Buffers;
 using System.Collections.Generic;
 using System.IO;
 using System.IO.Pipelines;
+using System.Linq;
 using System.Net.Http;
 using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Http.Features;
 using Microsoft.AspNetCore.Sockets.Client.Http;
 using Microsoft.AspNetCore.Sockets.Client.Internal;
-using Microsoft.AspNetCore.Sockets.Features;
 using Microsoft.AspNetCore.Sockets.Http.Internal;
 using Microsoft.AspNetCore.Sockets.Internal;
 using Microsoft.Extensions.Logging;
@@ -47,9 +47,6 @@ namespace Microsoft.AspNetCore.Sockets.Client
         private PipeWriter Output => _transportChannel.Output;
         private readonly List<ReceiveCallback> _callbacks = new List<ReceiveCallback>();
         private readonly TransportType _requestedTransportType = TransportType.All;
-        private TransportType _serverTransports = TransportType.All;
-        // The order of the transports here is the order determines the fallback order.
-        private static readonly TransportType[] AllTransports = new[]{ TransportType.WebSockets, TransportType.ServerSentEvents, TransportType.LongPolling };
         private readonly ConnectionLogScope _logScope;
         private readonly IDisposable _scopeDisposable;
 
@@ -153,9 +150,10 @@ namespace Microsoft.AspNetCore.Sockets.Client
             _scopeDisposable = _logger.BeginScope(_logScope);
         }
 
-        public async Task StartAsync() => await StartAsyncCore().ForceAsync();
+        public Task StartAsync() => StartAsync(TransferFormat.Binary);
+        public async Task StartAsync(TransferFormat transferFormat) => await StartAsyncCore(transferFormat).ForceAsync();
 
-        private Task StartAsyncCore()
+        private Task StartAsyncCore(TransferFormat transferFormat)
         {
             if (ChangeState(from: ConnectionState.Disconnected, to: ConnectionState.Connecting) != ConnectionState.Disconnected)
             {
@@ -166,7 +164,7 @@ namespace Microsoft.AspNetCore.Sockets.Client
             _startTcs = new TaskCompletionSource<object>(TaskCreationOptions.RunContinuationsAsynchronously);
             _eventQueue = new TaskQueue();
 
-            StartAsyncInternal()
+            StartAsyncInternal(transferFormat)
                 .ContinueWith(t =>
                 {
                     var abortException = _abortException;
@@ -195,7 +193,7 @@ namespace Microsoft.AspNetCore.Sockets.Client
             return negotiationResponse;
         }
 
-        private async Task StartAsyncInternal()
+        private async Task StartAsyncInternal(TransferFormat transferFormat)
         {
             Log.HttpConnectionStarting(_logger);
 
@@ -205,7 +203,7 @@ namespace Microsoft.AspNetCore.Sockets.Client
                 if (_requestedTransportType == TransportType.WebSockets)
                 {
                     Log.StartingTransport(_logger, _requestedTransportType, connectUrl);
-                    await StartTransport(connectUrl, _requestedTransportType);
+                    await StartTransport(connectUrl, _requestedTransportType, transferFormat);
                 }
                 else
                 {
@@ -219,14 +217,32 @@ namespace Microsoft.AspNetCore.Sockets.Client
                     }
 
                     // This should only need to happen once
-                    _serverTransports = GetAvailableServerTransports(negotiationResponse);
                     connectUrl = CreateConnectUrl(Url, negotiationResponse.ConnectionId);
 
-                    foreach (var transport in AllTransports)
+                    // We're going to search for the transfer format as a string because we don't want to parse
+                    // all the transfer formats in the negotiation response, and we want to allow transfer formats
+                    // we don't understand in the negotiate response.
+                    var transferFormatString = transferFormat.ToString();
+
+                    foreach (var transport in negotiationResponse.AvailableTransports)
                     {
+                        if (!Enum.TryParse<TransportType>(transport.Transport, out var transportType))
+                        {
+                            Log.TransportNotSupported(_logger, transport.Transport);
+                            continue;
+                        }
+
                         try
                         {
-                            if ((transport & _serverTransports & _requestedTransportType) != 0)
+                            if ((transportType & _requestedTransportType) == 0)
+                            {
+                                Log.TransportDisabledByClient(_logger, transportType);
+                            }
+                            else if (!transport.TransferFormats.Contains(transferFormatString, StringComparer.Ordinal))
+                            {
+                                Log.TransportDoesNotSupportTransferFormat(_logger, transportType, transferFormat);
+                            }
+                            else
                             {
                                 // The negotiation response gets cleared in the fallback scenario.
                                 if (negotiationResponse == null)
@@ -235,13 +251,14 @@ namespace Microsoft.AspNetCore.Sockets.Client
                                     connectUrl = CreateConnectUrl(Url, negotiationResponse.ConnectionId);
                                 }
 
-                                Log.StartingTransport(_logger, transport, connectUrl);
+                                Log.StartingTransport(_logger, transportType, connectUrl);
-                                await StartTransport(connectUrl, transport);
+                                await StartTransport(connectUrl, transportType, transferFormat);
                                 break;
                             }
                         }
-                        catch (Exception)
+                        catch (Exception ex)
                         {
+                            Log.TransportFailed(_logger, transportType, ex);
                             // Try the next transport
                             // Clear the negotiation response so we know to re-negotiate.
                             negotiationResponse = null;
@@ -382,22 +399,6 @@ namespace Microsoft.AspNetCore.Sockets.Client
             return negotiationResponse;
         }
 
-        private TransportType GetAvailableServerTransports(NegotiationResponse negotiationResponse)
-        {
-            if (negotiationResponse.AvailableTransports == null)
-            {
-                throw new FormatException("No transports returned in negotiation response.");
-            }
-
-            var availableServerTransports = (TransportType)0;
-            foreach (var t in negotiationResponse.AvailableTransports)
-            {
-                availableServerTransports |= t;
-            }
-
-            return availableServerTransports;
-        }
-
         private static Uri CreateConnectUrl(Uri url, string connectionId)
         {
             if (string.IsNullOrWhiteSpace(connectionId))
@@ -408,9 +409,8 @@ namespace Microsoft.AspNetCore.Sockets.Client
             return Utils.AppendQueryString(url, "id=" + connectionId);
         }
 
-        private async Task StartTransport(Uri connectUrl, TransportType transportType)
+        private async Task StartTransport(Uri connectUrl, TransportType transportType, TransferFormat transferFormat)
         {
-
             var options = new PipeOptions(writerScheduler: PipeScheduler.Inline, readerScheduler: PipeScheduler.ThreadPool, useSynchronizationContext: false);
             var pair = DuplexPipe.CreateConnectionPair(options, options);
             _transportChannel = pair.Transport;
@@ -419,15 +419,7 @@ namespace Microsoft.AspNetCore.Sockets.Client
             // Start the transport, giving it one end of the pipeline
             try
             {
-                await _transport.StartAsync(connectUrl, pair.Application, GetTransferMode(), this);
+                await _transport.StartAsync(connectUrl, pair.Application, transferFormat, this);
-
-                // actual transfer mode can differ from the one that was requested so set it on the feature
-                if (!_transport.Mode.HasValue)
-                {
-                    // This can happen with custom transports so it should be an exception, not an assert.
-                    throw new InvalidOperationException("Transport was expected to set the Mode property after StartAsync, but it has not been set.");
-                }
-                SetTransferMode(_transport.Mode.Value);
             }
             catch (Exception ex)
             {
@@ -437,29 +429,6 @@ namespace Microsoft.AspNetCore.Sockets.Client
             }
         }
 
-        private TransferMode GetTransferMode()
-        {
-            var transferModeFeature = Features.Get<ITransferModeFeature>();
-            if (transferModeFeature == null)
-            {
-                return TransferMode.Text;
-            }
-
-            return transferModeFeature.TransferMode;
-        }
-
-        private void SetTransferMode(TransferMode transferMode)
-        {
-            var transferModeFeature = Features.Get<ITransferModeFeature>();
-            if (transferModeFeature == null)
-            {
-                transferModeFeature = new TransferModeFeature();
-                Features.Set(transferModeFeature);
-            }
-
-            transferModeFeature.TransferMode = transferMode;
-        }
-
         private async Task ReceiveAsync()
         {
             try
@@ -753,7 +722,13 @@ namespace Microsoft.AspNetCore.Sockets.Client
         private class NegotiationResponse
         {
             public string ConnectionId { get; set; }
-            public TransportType[] AvailableTransports { get; set; }
+            public AvailableTransport[] AvailableTransports { get; set; }
+        }
+
+        private class AvailableTransport
+        {
+            public string Transport { get; set; }
+            public string[] TransferFormats { get; set; }
         }
     }
 }

src/Microsoft.AspNetCore.Sockets.Client.Http/ITransport.cs

@@ -9,8 +9,7 @@ namespace Microsoft.AspNetCore.Sockets.Client
 {
     public interface ITransport
     {
-        Task StartAsync(Uri url, IDuplexPipe application, TransferMode requestedTransferMode, IConnection connection);
+        Task StartAsync(Uri url, IDuplexPipe application, TransferFormat transferFormat, IConnection connection);
         Task StopAsync();
-        TransferMode? Mode { get; }
     }
 }

src/Microsoft.AspNetCore.Sockets.Client.Http/LongPollingTransport.Log.cs

@@ -10,8 +10,8 @@ namespace Microsoft.AspNetCore.Sockets.Client
     {
         private static class Log
         {
-            private static readonly Action<ILogger, TransferMode, Exception> _startTransport =
+            private static readonly Action<ILogger, TransferFormat, Exception> _startTransport =
-                LoggerMessage.Define<TransferMode>(LogLevel.Information, new EventId(1, "StartTransport"), "Starting transport. Transfer mode: {transferMode}.");
+                LoggerMessage.Define<TransferFormat>(LogLevel.Information, new EventId(1, "StartTransport"), "Starting transport. Transfer mode: {transferFormat}.");
 
             private static readonly Action<ILogger, Exception> _transportStopped =
                 LoggerMessage.Define(LogLevel.Debug, new EventId(2, "TransportStopped"), "Transport stopped.");
@@ -39,9 +39,9 @@ namespace Microsoft.AspNetCore.Sockets.Client
 
             // EventIds 100 - 106 used in SendUtils
 
-            public static void StartTransport(ILogger logger, TransferMode transferMode)
+            public static void StartTransport(ILogger logger, TransferFormat transferFormat)
             {
-                _startTransport(logger, transferMode, null);
+                _startTransport(logger, transferFormat, null);
             }
 
             public static void TransportStopped(ILogger logger, Exception exception)

src/Microsoft.AspNetCore.Sockets.Client.Http/LongPollingTransport.cs

@@ -27,8 +27,6 @@ namespace Microsoft.AspNetCore.Sockets.Client
 
         public Task Running { get; private set; } = Task.CompletedTask;
 
-        public TransferMode? Mode { get; private set; }
-
         public LongPollingTransport(HttpClient httpClient)
             : this(httpClient, null, null)
         { }
@@ -40,19 +38,18 @@ namespace Microsoft.AspNetCore.Sockets.Client
             _logger = (loggerFactory ?? NullLoggerFactory.Instance).CreateLogger<LongPollingTransport>();
         }
 
-        public Task StartAsync(Uri url, IDuplexPipe application, TransferMode requestedTransferMode, IConnection connection)
+        public Task StartAsync(Uri url, IDuplexPipe application, TransferFormat transferFormat, IConnection connection)
         {
-            if (requestedTransferMode != TransferMode.Binary && requestedTransferMode != TransferMode.Text)
+            if (transferFormat != TransferFormat.Binary && transferFormat != TransferFormat.Text)
             {
-                throw new ArgumentException("Invalid transfer mode.", nameof(requestedTransferMode));
+                throw new ArgumentException($"The '{transferFormat}' transfer format is not supported by this transport.", nameof(transferFormat));
             }
 
             connection.Features.Set<IConnectionInherentKeepAliveFeature>(new ConnectionInherentKeepAliveFeature(_httpClient.Timeout));
 
             _application = application;
-            Mode = requestedTransferMode;
 
-            Log.StartTransport(_logger, Mode.Value);
+            Log.StartTransport(_logger, transferFormat);
 
             // Start sending and polling (ask for binary if the server supports it)
             _poller = Poll(url, _transportCts.Token);

src/Microsoft.AspNetCore.Sockets.Client.Http/ServerSentEventsTransport.Log.cs

@@ -10,8 +10,8 @@ namespace Microsoft.AspNetCore.Sockets.Client
     {
         private static class Log
         {
-            private static readonly Action<ILogger, TransferMode, Exception> _startTransport =
+            private static readonly Action<ILogger, TransferFormat, Exception> _startTransport =
-                LoggerMessage.Define<TransferMode>(LogLevel.Information, new EventId(1, "StartTransport"), "Starting transport. Transfer mode: {transferMode}.");
+                LoggerMessage.Define<TransferFormat>(LogLevel.Information, new EventId(1, "StartTransport"), "Starting transport. Transfer mode: {transferFormat}.");
 
             private static readonly Action<ILogger, Exception> _transportStopped =
                 LoggerMessage.Define(LogLevel.Debug, new EventId(2, "TransportStopped"), "Transport stopped.");
@@ -39,9 +39,9 @@ namespace Microsoft.AspNetCore.Sockets.Client
 
             // EventIds 100 - 106 used in SendUtils
 
-            public static void StartTransport(ILogger logger, TransferMode transferMode)
+            public static void StartTransport(ILogger logger, TransferFormat transferFormat)
             {
-                _startTransport(logger, transferMode, null);
+                _startTransport(logger, transferFormat, null);
             }
 
             public static void TransportStopped(ILogger logger, Exception exception)

src/Microsoft.AspNetCore.Sockets.Client.Http/ServerSentEventsTransport.cs

@@ -26,8 +26,6 @@ namespace Microsoft.AspNetCore.Sockets.Client
 
         public Task Running { get; private set; } = Task.CompletedTask;
 
-        public TransferMode? Mode { get; private set; }
-
         public ServerSentEventsTransport(HttpClient httpClient)
             : this(httpClient, null, null)
         { }
@@ -44,17 +42,16 @@ namespace Microsoft.AspNetCore.Sockets.Client
             _logger = (loggerFactory ?? NullLoggerFactory.Instance).CreateLogger<ServerSentEventsTransport>();
         }
 
-        public Task StartAsync(Uri url, IDuplexPipe application, TransferMode requestedTransferMode, IConnection connection)
+        public Task StartAsync(Uri url, IDuplexPipe application, TransferFormat transferFormat, IConnection connection)
         {
-            if (requestedTransferMode != TransferMode.Binary && requestedTransferMode != TransferMode.Text)
+            if (transferFormat != TransferFormat.Text)
             {
-                throw new ArgumentException("Invalid transfer mode.", nameof(requestedTransferMode));
+                throw new ArgumentException($"The '{transferFormat}' transfer format is not supported by this transport.", nameof(transferFormat));
             }
 
             _application = application;
-            Mode = TransferMode.Text; // Server Sent Events is a text only transport
 
-            Log.StartTransport(_logger, Mode.Value);
+            Log.StartTransport(_logger, transferFormat);
 
             var sendTask = SendUtils.SendMessages(url, _application, _httpClient, _httpOptions, _transportCts, _logger);
             var receiveTask = OpenConnection(_application, url, _transportCts.Token);

src/Microsoft.AspNetCore.Sockets.Client.Http/TransferModeFeature.cs

@@ -1,12 +0,0 @@
-// Copyright (c) .NET Foundation. All rights reserved.
-// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
-
-using Microsoft.AspNetCore.Sockets.Features;
-
-namespace Microsoft.AspNetCore.Sockets.Client
-{
-    public class TransferModeFeature : ITransferModeFeature
-    {
-        public TransferMode TransferMode { get; set; }
-    }
-}

src/Microsoft.AspNetCore.Sockets.Client.Http/WebSocketsTransport.Log.cs

@@ -1,4 +1,4 @@
-// Copyright (c) .NET Foundation. All rights reserved.
+// Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
@@ -11,8 +11,8 @@ namespace Microsoft.AspNetCore.Sockets.Client
     {
         private static class Log
         {
-            private static readonly Action<ILogger, TransferMode, Exception> _startTransport =
+            private static readonly Action<ILogger, TransferFormat, Exception> _startTransport =
-                LoggerMessage.Define<TransferMode>(LogLevel.Information, new EventId(1, "StartTransport"), "Starting transport. Transfer mode: {transferMode}.");
+                LoggerMessage.Define<TransferFormat>(LogLevel.Information, new EventId(1, "StartTransport"), "Starting transport. Transfer mode: {transferFormat}.");
 
             private static readonly Action<ILogger, Exception> _transportStopped =
                 LoggerMessage.Define(LogLevel.Debug, new EventId(2, "TransportStopped"), "Transport stopped.");
@@ -65,9 +65,9 @@ namespace Microsoft.AspNetCore.Sockets.Client
             private static readonly Action<ILogger, Exception> _cancelMessage =
                 LoggerMessage.Define(LogLevel.Debug, new EventId(18, "CancelMessage"), "Canceled passing message to application.");
 
-            public static void StartTransport(ILogger logger, TransferMode transferMode)
+            public static void StartTransport(ILogger logger, TransferFormat transferFormat)
             {
-                _startTransport(logger, transferMode, null);
+                _startTransport(logger, transferFormat, null);
             }
 
             public static void TransportStopped(ILogger logger, Exception exception)

src/Microsoft.AspNetCore.Sockets.Client.Http/WebSocketsTransport.cs

@@ -19,14 +19,13 @@ namespace Microsoft.AspNetCore.Sockets.Client
     {
         private readonly ClientWebSocket _webSocket;
         private IDuplexPipe _application;
+        private WebSocketMessageType _webSocketMessageType;
         private readonly ILogger _logger;
         private readonly TimeSpan _closeTimeout;
         private volatile bool _aborted;
 
         public Task Running { get; private set; } = Task.CompletedTask;
 
-        public TransferMode? Mode { get; private set; }
-
         public WebSocketsTransport()
             : this(null, null)
         {
@@ -87,7 +86,7 @@ namespace Microsoft.AspNetCore.Sockets.Client
             _logger = (loggerFactory ?? NullLoggerFactory.Instance).CreateLogger<WebSocketsTransport>();
         }
 
-        public async Task StartAsync(Uri url, IDuplexPipe application, TransferMode requestedTransferMode, IConnection connection)
+        public async Task StartAsync(Uri url, IDuplexPipe application, TransferFormat transferFormat, IConnection connection)
         {
             if (url == null)
             {
@@ -99,15 +98,18 @@ namespace Microsoft.AspNetCore.Sockets.Client
                 throw new ArgumentNullException(nameof(application));
             }
 
-            if (requestedTransferMode != TransferMode.Binary && requestedTransferMode != TransferMode.Text)
+            if (transferFormat != TransferFormat.Binary && transferFormat != TransferFormat.Text)
             {
-                throw new ArgumentException("Invalid transfer mode.", nameof(requestedTransferMode));
+                throw new ArgumentException($"The '{transferFormat}' transfer format is not supported by this transport.", nameof(transferFormat));
             }
 
             _application = application;
-            Mode = requestedTransferMode;
+            _webSocketMessageType = transferFormat == TransferFormat.Binary
+                ? WebSocketMessageType.Binary
+                : WebSocketMessageType.Text;
 
-            Log.StartTransport(_logger, Mode.Value);
+
+            Log.StartTransport(_logger, transferFormat);
 
             await Connect(url);
 
@@ -243,11 +245,6 @@ namespace Microsoft.AspNetCore.Sockets.Client
 
         private async Task StartSending(WebSocket socket)
         {
-            var webSocketMessageType =
-                Mode == TransferMode.Binary
-                    ? WebSocketMessageType.Binary
-                    : WebSocketMessageType.Text;
-
             Exception error = null;
 
             try
@@ -274,7 +271,7 @@ namespace Microsoft.AspNetCore.Sockets.Client
 
                                 if (WebSocketCanSend(socket))
                                 {
-                                    await socket.SendAsync(buffer, webSocketMessageType);
+                                    await socket.SendAsync(buffer, _webSocketMessageType);
                                 }
                                 else
                                 {

src/Microsoft.AspNetCore.Sockets.Http/HttpConnectionDispatcher.cs

@@ -115,7 +115,7 @@ namespace Microsoft.AspNetCore.Sockets
                 Log.EstablishedConnection(_logger);
 
                 // ServerSentEvents is a text protocol only
-                connection.TransportCapabilities = TransferMode.Text;
+                connection.SupportedFormats = TransferFormat.Text;
 
                 // We only need to provide the Input channel since writing to the application is handled through /send.
                 var sse = new ServerSentEventsTransport(connection.Application.Input, connection.ConnectionId, _loggerFactory);
@@ -389,15 +389,15 @@ namespace Microsoft.AspNetCore.Sockets
                 jsonWriter.WriteStartArray();
                 if ((options.Transports & TransportType.WebSockets) != 0)
                 {
-                    jsonWriter.WriteValue(nameof(TransportType.WebSockets));
+                    WriteTransport(jsonWriter, nameof(TransportType.WebSockets), TransferFormat.Text | TransferFormat.Binary);
                 }
                 if ((options.Transports & TransportType.ServerSentEvents) != 0)
                 {
-                    jsonWriter.WriteValue(nameof(TransportType.ServerSentEvents));
+                    WriteTransport(jsonWriter, nameof(TransportType.ServerSentEvents), TransferFormat.Text);
                 }
                 if ((options.Transports & TransportType.LongPolling) != 0)
                 {
-                    jsonWriter.WriteValue(nameof(TransportType.LongPolling));
+                    WriteTransport(jsonWriter, nameof(TransportType.LongPolling), TransferFormat.Text | TransferFormat.Binary);
                 }
                 jsonWriter.WriteEndArray();
                 jsonWriter.WriteEndObject();
@@ -406,6 +406,27 @@ namespace Microsoft.AspNetCore.Sockets
             return sb.ToString();
         }
 
+        private static void WriteTransport(JsonWriter writer, string transportName, TransferFormat supportedTransferFormats)
+        {
+            writer.WriteStartObject();
+            writer.WritePropertyName("transport");
+            writer.WriteValue(transportName);
+            writer.WritePropertyName("transferFormats");
+            writer.WriteStartArray();
+            if ((supportedTransferFormats & TransferFormat.Binary) != 0)
+            {
+                writer.WriteValue(nameof(TransferFormat.Binary));
+            }
+
+            if ((supportedTransferFormats & TransferFormat.Text) != 0)
+            {
+                writer.WriteValue(nameof(TransferFormat.Text));
+            }
+
+            writer.WriteEndArray();
+            writer.WriteEndObject();
+        }
+
         private static string GetConnectionId(HttpContext context) => context.Request.Query["id"];
 
         private async Task ProcessSend(HttpContext context)
@@ -477,9 +498,6 @@ namespace Microsoft.AspNetCore.Sockets
             connection.User = context.User;
             connection.SetHttpContext(context);
 
-            // this is the default setting which should be overwritten by transports that have different capabilities (e.g. SSE)
-            connection.TransportCapabilities = TransferMode.Binary | TransferMode.Text;
-
             // Set the Connection ID on the logging scope so that logs from now on will have the
             // Connection ID metadata set.
             logScope.ConnectionId = connection.ConnectionId;

src/Microsoft.AspNetCore.Sockets.Http/Internal/Transports/WebSocketsTransport.cs

@@ -220,7 +220,7 @@ namespace Microsoft.AspNetCore.Sockets.Internal.Transports
                             {
                                 Log.SendPayload(_logger, buffer.Length);
 
-                                var webSocketMessageType = (_connection.TransferMode == TransferMode.Binary
+                                var webSocketMessageType = (_connection.ActiveFormat == TransferFormat.Binary
                                     ? WebSocketMessageType.Binary
                                     : WebSocketMessageType.Text);
 

src/Microsoft.AspNetCore.Sockets/DefaultConnectionContext.cs

@@ -2,7 +2,6 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
-using System.Buffers;
 using System.Collections.Generic;
 using System.IO.Pipelines;
 using System.Security.Claims;
@@ -21,7 +20,7 @@ namespace Microsoft.AspNetCore.Sockets
                                             IConnectionTransportFeature,
                                             IConnectionUserFeature,
                                             IConnectionHeartbeatFeature,
-                                            ITransferModeFeature
+                                            ITransferFormatFeature
     {
         private List<(Action<object> handler, object state)> _heartbeatHandlers = new List<(Action<object> handler, object state)>();
 
@@ -37,14 +36,18 @@ namespace Microsoft.AspNetCore.Sockets
             ConnectionId = id;
             LastSeenUtc = DateTime.UtcNow;
 
+            // The default behavior is that both formats are supported.
+            SupportedFormats = TransferFormat.Binary | TransferFormat.Text;
+            ActiveFormat = TransferFormat.Text;
+
             // PERF: This type could just implement IFeatureCollection
             Features = new FeatureCollection();
             Features.Set<IConnectionUserFeature>(this);
             Features.Set<IConnectionMetadataFeature>(this);
             Features.Set<IConnectionIdFeature>(this);
             Features.Set<IConnectionTransportFeature>(this);
-            Features.Set<ITransferModeFeature>(this);
             Features.Set<IConnectionHeartbeatFeature>(this);
+            Features.Set<ITransferFormatFeature>(this);
         }
 
         public CancellationTokenSource Cancellation { get; set; }
@@ -71,9 +74,9 @@ namespace Microsoft.AspNetCore.Sockets
 
         public override IDuplexPipe Transport { get; set; }
 
-        public TransferMode TransportCapabilities { get; set; }
+        public TransferFormat SupportedFormats { get; set; }
 
-        public TransferMode TransferMode { get; set; }
+        public TransferFormat ActiveFormat { get; set; }
 
         public void OnHeartbeat(Action<object> action, object state)
         {

test/Microsoft.AspNetCore.SignalR.Client.FunctionalTests/HubConnectionTests.cs

@@ -58,7 +58,7 @@ namespace Microsoft.AspNetCore.SignalR.Client.FunctionalTests
                 {
                     await connection.StartAsync().OrTimeout();
 
-                    var result = await connection.InvokeAsync<string>("HelloWorld").OrTimeout();
+                    var result = await connection.InvokeAsync<string>(nameof(TestHub.HelloWorld)).OrTimeout();
 
                     Assert.Equal("Hello World!", result);
                 }
@@ -87,7 +87,7 @@ namespace Microsoft.AspNetCore.SignalR.Client.FunctionalTests
                 {
                     await connection.StartAsync().OrTimeout();
 
-                    var result = await connection.InvokeAsync<string>("Echo", originalMessage).OrTimeout();
+                    var result = await connection.InvokeAsync<string>(nameof(TestHub.Echo), originalMessage).OrTimeout();
 
                     Assert.Equal(originalMessage, result);
                 }
@@ -115,11 +115,11 @@ namespace Microsoft.AspNetCore.SignalR.Client.FunctionalTests
                 try
                 {
                     await connection.StartAsync().OrTimeout();
-                    var result = await connection.InvokeAsync<string>("Echo", originalMessage).OrTimeout();
+                    var result = await connection.InvokeAsync<string>(nameof(TestHub.Echo), originalMessage).OrTimeout();
                     Assert.Equal(originalMessage, result);
                     await connection.StopAsync().OrTimeout();
                     await connection.StartAsync().OrTimeout();
-                    result = await connection.InvokeAsync<string>("Echo", originalMessage).OrTimeout();
+                    result = await connection.InvokeAsync<string>(nameof(TestHub.Echo), originalMessage).OrTimeout();
                     Assert.Equal(originalMessage, result);
                 }
                 catch (Exception ex)
@@ -159,7 +159,7 @@ namespace Microsoft.AspNetCore.SignalR.Client.FunctionalTests
                 try
                 {
                     await connection.StartAsync().OrTimeout();
-                    var result = await connection.InvokeAsync<string>("Echo", originalMessage).OrTimeout();
+                    var result = await connection.InvokeAsync<string>(nameof(TestHub.Echo), originalMessage).OrTimeout();
                     Assert.Equal(originalMessage, result);
 
                     logger.LogInformation("Stopping connection");
@@ -169,7 +169,7 @@ namespace Microsoft.AspNetCore.SignalR.Client.FunctionalTests
                     await restartTcs.Task.OrTimeout();
                     logger.LogInformation("Reconnection complete");
 
-                    result = await connection.InvokeAsync<string>("Echo", originalMessage).OrTimeout();
+                    result = await connection.InvokeAsync<string>(nameof(TestHub.Echo), originalMessage).OrTimeout();
                     Assert.Equal(originalMessage, result);
 
                 }
@@ -199,7 +199,7 @@ namespace Microsoft.AspNetCore.SignalR.Client.FunctionalTests
                 {
                     await connection.StartAsync().OrTimeout();
 
-                    var result = await connection.InvokeAsync<string>("echo", originalMessage).OrTimeout();
+                    var result = await connection.InvokeAsync<string>(nameof(TestHub.Echo).ToLowerInvariant(), originalMessage).OrTimeout();
 
                     Assert.Equal(originalMessage, result);
                 }
@@ -677,7 +677,7 @@ namespace Microsoft.AspNetCore.SignalR.Client.FunctionalTests
                 try
                 {
                     await hubConnection.StartAsync().OrTimeout();
-                    var message = await hubConnection.InvokeAsync<string>("Echo", "Hello, World!").OrTimeout();
+                    var message = await hubConnection.InvokeAsync<string>(nameof(TestHub.Echo), "Hello, World!").OrTimeout();
                     Assert.Equal("Hello, World!", message);
                 }
                 catch (Exception ex)
@@ -708,7 +708,7 @@ namespace Microsoft.AspNetCore.SignalR.Client.FunctionalTests
                 try
                 {
                     await hubConnection.StartAsync().OrTimeout();
-                    var headerValues = await hubConnection.InvokeAsync<string[]>("GetHeaderValues", new object[] { new[] { "X-test", "X-42" } }).OrTimeout();
+                    var headerValues = await hubConnection.InvokeAsync<string[]>(nameof(TestHub.GetHeaderValues), new object[] { new[] { "X-test", "X-42" } }).OrTimeout();
                     Assert.Equal(new[] { "42", "test" }, headerValues);
                 }
                 catch (Exception ex)
@@ -742,7 +742,7 @@ namespace Microsoft.AspNetCore.SignalR.Client.FunctionalTests
                 try
                 {
                     await hubConnection.StartAsync().OrTimeout();
-                    var cookieValue = await hubConnection.InvokeAsync<string>("GetCookieValue", new object[] { "Foo" }).OrTimeout();
+                    var cookieValue = await hubConnection.InvokeAsync<string>(nameof(TestHub.GetCookieValue), new object[] { "Foo" }).OrTimeout();
                     Assert.Equal("Bar", cookieValue);
                 }
                 catch (Exception ex)
@@ -772,7 +772,7 @@ namespace Microsoft.AspNetCore.SignalR.Client.FunctionalTests
                 {
                     await hubConnection.StartAsync().OrTimeout();
 
-                    var features = await hubConnection.InvokeAsync<object[]>("GetIHttpConnectionFeatureProperties").OrTimeout();
+                    var features = await hubConnection.InvokeAsync<object[]>(nameof(TestHub.GetIHttpConnectionFeatureProperties)).OrTimeout();
                     var localPort = (Int64)features[0];
                     var remotePort = (Int64)features[1];
                     var localIP = (string)features[2];
@@ -795,23 +795,56 @@ namespace Microsoft.AspNetCore.SignalR.Client.FunctionalTests
             }
         }
 
+        [Fact]
+        public async Task NegotiationSkipsServerSentEventsWhenUsingBinaryProtocol()
+        {
+            using (StartLog(out var loggerFactory))
+            {
+                var hubConnection = new HubConnectionBuilder()
+                    .WithUrl(_serverFixture.Url + "/default-nowebsockets")
+                    .WithHubProtocol(new MessagePackHubProtocol())
+                    .WithLoggerFactory(loggerFactory)
+                    .Build();
+                try
+                {
+                    await hubConnection.StartAsync().OrTimeout();
+
+                    var transport = await hubConnection.InvokeAsync<TransportType>(nameof(TestHub.GetActiveTransportName)).OrTimeout();
+                    Assert.Equal(TransportType.LongPolling, transport);
+                }
+                catch (Exception ex)
+                {
+                    loggerFactory.CreateLogger<HubConnectionTests>().LogError(ex, "Exception from test");
+                    throw;
+                }
+                finally
+                {
+                    await hubConnection.DisposeAsync().OrTimeout();
+                }
+            }
+        }
+
         public static IEnumerable<object[]> HubProtocolsAndTransportsAndHubPaths
         {
             get
             {
                 foreach (var protocol in HubProtocols)
                 {
-                    foreach (var transport in TransportTypes().SelectMany(t => t))
+                    foreach (var transport in TransportTypes().SelectMany(t => t).Cast<TransportType>())
                     {
                         foreach (var hubPath in HubPaths)
                         {
-                            yield return new object[] { protocol, transport, hubPath };
+                            if (!(protocol is MessagePackHubProtocol) || transport != TransportType.ServerSentEvents)
+                            {
+                                yield return new object[] { protocol, transport, hubPath };
+                            }
                         }
                     }
                 }
             }
         }
 
+        // This list excludes "special" hub paths like "default-nowebsockets" which exist for specific tests.
         public static string[] HubPaths = new[] { "/default", "/dynamic", "/hubT" };
 
         public static IEnumerable<IHubProtocol> HubProtocols =>

test/Microsoft.AspNetCore.SignalR.Client.FunctionalTests/Hubs.cs

@@ -9,6 +9,7 @@ using System.Threading.Channels;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Authentication.JwtBearer;
 using Microsoft.AspNetCore.Authorization;
+using Microsoft.AspNetCore.Sockets;
 
 namespace Microsoft.AspNetCore.SignalR.Client.FunctionalTests
 {
@@ -57,6 +58,11 @@ namespace Microsoft.AspNetCore.SignalR.Client.FunctionalTests
 
             return result;
         }
+
+        public string GetActiveTransportName()
+        {
+            return Context.Connection.Metadata[ConnectionMetadataNames.Transport].ToString();
+        }
     }
 
     public class DynamicTestHub : DynamicHub

test/Microsoft.AspNetCore.SignalR.Client.FunctionalTests/Startup.cs

@@ -7,6 +7,7 @@ using System.Security.Claims;
 using Microsoft.AspNetCore.Authentication.JwtBearer;
 using Microsoft.AspNetCore.Builder;
 using Microsoft.AspNetCore.Http;
+using Microsoft.AspNetCore.Sockets;
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.IdentityModel.Tokens;
 
@@ -54,6 +55,7 @@ namespace Microsoft.AspNetCore.SignalR.Client.FunctionalTests
                 routes.MapHub<DynamicTestHub>("/dynamic");
                 routes.MapHub<TestHubT>("/hubT");
                 routes.MapHub<HubWithAuthorization>("/authorizedhub");
+                routes.MapHub<TestHub>("/default-nowebsockets", options => options.Transports = TransportType.LongPolling | TransportType.ServerSentEvents);
             });
 
             app.Run(async (context) =>

test/Microsoft.AspNetCore.SignalR.Client.Tests/HttpConnectionTests.AbortAsync.cs

@@ -3,6 +3,7 @@
 
 using System;
 using System.Threading.Tasks;
+using Microsoft.AspNetCore.Sockets;
 using Xunit;
 
 namespace Microsoft.AspNetCore.SignalR.Client.Tests
@@ -18,7 +19,7 @@ namespace Microsoft.AspNetCore.SignalR.Client.Tests
                 return WithConnectionAsync(CreateConnection(), async (connection, closed) =>
                 {
                     // Start the connection
-                    await connection.StartAsync().OrTimeout();
+                    await connection.StartAsync(TransferFormat.Text).OrTimeout();
 
                     // Abort with an error
                     var expected = new Exception("Ruh roh!");
@@ -36,7 +37,7 @@ namespace Microsoft.AspNetCore.SignalR.Client.Tests
                 return WithConnectionAsync(CreateConnection(transport: new TestTransport(onTransportStop: SyncPoint.Create(2, out var syncPoints))), async (connection, closed) =>
                 {
                     // Start the connection
-                    await connection.StartAsync().OrTimeout();
+                    await connection.StartAsync(TransferFormat.Text).OrTimeout();
 
                     // Stop normally
                     var stopTask = connection.StopAsync().OrTimeout();
@@ -70,7 +71,7 @@ namespace Microsoft.AspNetCore.SignalR.Client.Tests
                 return WithConnectionAsync(CreateConnection(transport: new TestTransport(onTransportStop: SyncPoint.Create(2, out var syncPoints))), async (connection, closed) =>
                 {
                     // Start the connection
-                    await connection.StartAsync().OrTimeout();
+                    await connection.StartAsync(TransferFormat.Text).OrTimeout();
 
                     // Abort with an error
                     var expected = new Exception("Ruh roh!");
@@ -97,7 +98,7 @@ namespace Microsoft.AspNetCore.SignalR.Client.Tests
                 return WithConnectionAsync(CreateConnection(transport: new TestTransport(onTransportStop: SyncPoint.Create(out var syncPoint))), async (connection, closed) =>
                 {
                     // Start the connection
-                    await connection.StartAsync().OrTimeout();
+                    await connection.StartAsync(TransferFormat.Text).OrTimeout();
 
                     // Abort with an error
                     var expected = new Exception("Ruh roh!");
@@ -106,7 +107,7 @@ namespace Microsoft.AspNetCore.SignalR.Client.Tests
                     // Wait to reach the first sync point
                     await syncPoint.WaitForSyncPoint().OrTimeout();
 
-                    var ex = await Assert.ThrowsAsync<InvalidOperationException>(() => connection.StartAsync().OrTimeout());
+                    var ex = await Assert.ThrowsAsync<InvalidOperationException>(() => connection.StartAsync(TransferFormat.Text).OrTimeout());
                     Assert.Equal("Cannot start a connection that is not in the Disconnected state.", ex.Message);
 
                     // Release the sync point and wait for close to complete
@@ -117,7 +118,7 @@ namespace Microsoft.AspNetCore.SignalR.Client.Tests
                     Assert.Same(expected, actual);
 
                     // We can start now
-                    await connection.StartAsync().OrTimeout();
+                    await connection.StartAsync(TransferFormat.Text).OrTimeout();
 
                     // And we can stop without getting the abort exception.
                     await connection.StopAsync().OrTimeout();

test/Microsoft.AspNetCore.SignalR.Client.Tests/HttpConnectionTests.ConnectionLifecycle.cs

@@ -6,6 +6,7 @@ using System.Net;
 using System.Net.Http;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Client.Tests;
+using Microsoft.AspNetCore.Sockets;
 using Microsoft.AspNetCore.Sockets.Client;
 using Microsoft.Extensions.Logging.Testing;
 using Xunit;
@@ -28,10 +29,10 @@ namespace Microsoft.AspNetCore.SignalR.Client.Tests
                 {
                     await WithConnectionAsync(CreateConnection(loggerFactory: loggerFactory), async (connection, closed) =>
                     {
-                        await connection.StartAsync().OrTimeout();
+                        await connection.StartAsync(TransferFormat.Text).OrTimeout();
                         var exception =
                             await Assert.ThrowsAsync<InvalidOperationException>(
-                                async () => await connection.StartAsync().OrTimeout());
+                                async () => await connection.StartAsync(TransferFormat.Text).OrTimeout());
                         Assert.Equal("Cannot start a connection that is not in the Disconnected state.", exception.Message);
                     });
                 }
@@ -47,11 +48,11 @@ namespace Microsoft.AspNetCore.SignalR.Client.Tests
                         CreateConnection(loggerFactory: loggerFactory),
                         async (connection, closed) =>
                         {
-                            await connection.StartAsync().OrTimeout();
+                            await connection.StartAsync(TransferFormat.Text).OrTimeout();
                             await connection.DisposeAsync();
                             var exception =
                                 await Assert.ThrowsAsync<InvalidOperationException>(
-                                    async () => await connection.StartAsync().OrTimeout());
+                                    async () => await connection.StartAsync(TransferFormat.Text).OrTimeout());
 
                             Assert.Equal("Cannot start a connection that is not in the Disconnected state.", exception.Message);
                         });
@@ -70,7 +71,7 @@ namespace Microsoft.AspNetCore.SignalR.Client.Tests
                             await connection.DisposeAsync();
                             var exception =
                                 await Assert.ThrowsAsync<InvalidOperationException>(
-                                    async () => await connection.StartAsync().OrTimeout());
+                                    async () => await connection.StartAsync(TransferFormat.Text).OrTimeout());
 
                             Assert.Equal("Cannot start a connection that is not in the Disconnected state.", exception.Message);
                         });
@@ -91,7 +92,7 @@ namespace Microsoft.AspNetCore.SignalR.Client.Tests
                         async (connection, closed) =>
                     {
                         // Start the connection and wait for the transport to start up.
-                        var startTask = connection.StartAsync();
+                        var startTask = connection.StartAsync(TransferFormat.Text);
                         await transportStart.WaitForSyncPoint().OrTimeout();
 
                         // While the transport is starting, dispose the connection
@@ -139,7 +140,7 @@ namespace Microsoft.AspNetCore.SignalR.Client.Tests
                         async (connection, closed) =>
                     {
                         Assert.Equal(0, startCounter);
-                        await connection.StartAsync();
+                        await connection.StartAsync(TransferFormat.Text);
                         Assert.Equal(passThreshold, startCounter);
                     });
                 }
@@ -164,7 +165,7 @@ namespace Microsoft.AspNetCore.SignalR.Client.Tests
                             transport: new TestTransport(onTransportStart: OnTransportStart)),
                         async (connection, closed) =>
                         {
-                            var ex = await Assert.ThrowsAsync<InvalidOperationException>(() => connection.StartAsync());
+                            var ex = await Assert.ThrowsAsync<InvalidOperationException>(() => connection.StartAsync(TransferFormat.Text));
                             Assert.Equal("Unable to connect to the server with any of the available transports.", ex.Message);
                             Assert.Equal(3, startCounter);
                         });
@@ -180,9 +181,9 @@ namespace Microsoft.AspNetCore.SignalR.Client.Tests
                         CreateConnection(loggerFactory: loggerFactory),
                         async (connection, closed) =>
                     {
-                        await connection.StartAsync().OrTimeout();
+                        await connection.StartAsync(TransferFormat.Text).OrTimeout();
                         await connection.StopAsync().OrTimeout();
-                        await connection.StartAsync().OrTimeout();
+                        await connection.StartAsync(TransferFormat.Text).OrTimeout();
                     });
                 }
             }
@@ -199,7 +200,7 @@ namespace Microsoft.AspNetCore.SignalR.Client.Tests
                         async (connection, closed) =>
                     {
                         // Start and wait for the transport to start up.
-                        var startTask = connection.StartAsync();
+                        var startTask = connection.StartAsync(TransferFormat.Text);
                         await transportStart.WaitForSyncPoint().OrTimeout();
 
                         // Stop the connection while it's starting
@@ -223,7 +224,7 @@ namespace Microsoft.AspNetCore.SignalR.Client.Tests
                         CreateConnection(loggerFactory: loggerFactory),
                         async (connection, closed) =>
                     {
-                        await connection.StartAsync().OrTimeout();
+                        await connection.StartAsync(TransferFormat.Text).OrTimeout();
                         await Task.WhenAll(connection.StopAsync(), connection.StopAsync()).OrTimeout();
                         await closed.OrTimeout();
                     });
@@ -257,14 +258,14 @@ namespace Microsoft.AspNetCore.SignalR.Client.Tests
                         CreateConnection(httpHandler, loggerFactory),
                         async (connection, closed) =>
                     {
-                        await connection.StartAsync().OrTimeout();
+                        await connection.StartAsync(TransferFormat.Text).OrTimeout();
                         await connection.SendAsync(new byte[] { 0x42 }).OrTimeout();
 
                         // Wait for the connection to close, because the send failed.
                         await Assert.ThrowsAsync<HttpRequestException>(() => closed.OrTimeout());
 
                         // Start it up again
-                        await connection.StartAsync().OrTimeout();
+                        await connection.StartAsync(TransferFormat.Text).OrTimeout();
                     });
                 }
             }
@@ -281,7 +282,7 @@ namespace Microsoft.AspNetCore.SignalR.Client.Tests
                         async (connection, closed) =>
                     {
                         // Start the connection
-                        await connection.StartAsync().OrTimeout();
+                        await connection.StartAsync(TransferFormat.Text).OrTimeout();
 
                         // Stop the connection
                         var stopTask = connection.StopAsync().OrTimeout();
@@ -299,7 +300,7 @@ namespace Microsoft.AspNetCore.SignalR.Client.Tests
                         await disposeTask.OrTimeout();
 
                         // We should be disposed and thus unable to restart.
-                        var exception = await Assert.ThrowsAsync<InvalidOperationException>(() => connection.StartAsync().OrTimeout());
+                        var exception = await Assert.ThrowsAsync<InvalidOperationException>(() => connection.StartAsync(TransferFormat.Text).OrTimeout());
                         Assert.Equal("Cannot start a connection that is not in the Disconnected state.", exception.Message);
                     });
                 }
@@ -314,7 +315,7 @@ namespace Microsoft.AspNetCore.SignalR.Client.Tests
                         CreateConnection(loggerFactory: loggerFactory),
                         async (connection, closed) =>
                         {
-                            await connection.StartAsync().OrTimeout();
+                            await connection.StartAsync(TransferFormat.Text).OrTimeout();
                             await connection.StopAsync().OrTimeout();
                             await closed.OrTimeout();
                             await connection.DisposeAsync().OrTimeout();
@@ -329,7 +330,7 @@ namespace Microsoft.AspNetCore.SignalR.Client.Tests
                     CreateConnection(),
                     async (connection, closed) =>
                     {
-                        await connection.StartAsync().OrTimeout();
+                        await connection.StartAsync(TransferFormat.Text).OrTimeout();
                         await connection.DisposeAsync().OrTimeout();
                         await closed.OrTimeout();
                     });
@@ -346,7 +347,7 @@ namespace Microsoft.AspNetCore.SignalR.Client.Tests
                     CreateConnection(transport: testTransport),
                 async (connection, closed) =>
                 {
-                    await connection.StartAsync().OrTimeout();
+                    await connection.StartAsync(TransferFormat.Text).OrTimeout();
                     testTransport.Application.Output.Complete(expected);
                     var actual = await Assert.ThrowsAsync<Exception>(() => closed.OrTimeout());
                     Assert.Same(expected, actual);
@@ -384,7 +385,7 @@ namespace Microsoft.AspNetCore.SignalR.Client.Tests
                         async (connection, closed) =>
                         {
                             // Start the transport
-                            await connection.StartAsync().OrTimeout();
+                            await connection.StartAsync(TransferFormat.Text).OrTimeout();
                             Assert.False(longPollingTransport.Running.IsCompleted, "Expected that the transport would still be running");
 
                             // Stop the connection, and we should stop the transport

test/Microsoft.AspNetCore.SignalR.Client.Tests/HttpConnectionTests.Helpers.cs

@@ -14,26 +14,33 @@ namespace Microsoft.AspNetCore.SignalR.Client.Tests
 {
     public partial class HttpConnectionTests
     {
-        private static HttpConnection CreateConnection(HttpMessageHandler httpHandler = null, ILoggerFactory loggerFactory = null, string url = null, ITransport transport = null)
+        private static HttpConnection CreateConnection(HttpMessageHandler httpHandler = null, ILoggerFactory loggerFactory = null, string url = null, ITransport transport = null, ITransportFactory transportFactory = null)
         {
             var httpOptions = new HttpOptions()
             {
                 HttpMessageHandler = (httpMessageHandler) => httpHandler ?? TestHttpMessageHandler.CreateDefault(),
             };
 
-            return CreateConnection(httpOptions, loggerFactory, url, transport);
+            return CreateConnection(httpOptions, loggerFactory, url, transport, transportFactory);
         }
 
-        private static HttpConnection CreateConnection(HttpOptions httpOptions, ILoggerFactory loggerFactory = null, string url = null, ITransport transport = null)
+        private static HttpConnection CreateConnection(HttpOptions httpOptions, ILoggerFactory loggerFactory = null, string url = null, ITransport transport = null, ITransportFactory transportFactory = null)
         {
             loggerFactory = loggerFactory ?? NullLoggerFactory.Instance;
             var uri = new Uri(url ?? "http://fakeuri.org/");
 
-            var connection = (transport != null) ?
+            if (transportFactory != null)
-                new HttpConnection(uri, new TestTransportFactory(transport), loggerFactory, httpOptions) :
+            {
-                new HttpConnection(uri, TransportType.LongPolling, loggerFactory, httpOptions);
+                return new HttpConnection(uri, transportFactory, loggerFactory, httpOptions);
-
+            }
-            return connection;
+            else if (transport != null)
+            {
+                return new HttpConnection(uri, new TestTransportFactory(transport), loggerFactory, httpOptions);
+            }
+            else
+            {
+                return new HttpConnection(uri, TransportType.LongPolling, loggerFactory, httpOptions);
+            }
         }
 
         private static async Task WithConnectionAsync(HttpConnection connection, Func<HttpConnection, Task, Task> body)

test/Microsoft.AspNetCore.SignalR.Client.Tests/HttpConnectionTests.Negotiate.cs

@@ -5,6 +5,10 @@ using System;
 using System.Net;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Client.Tests;
+using Microsoft.AspNetCore.Sockets;
+using Microsoft.AspNetCore.Sockets.Client;
+using Moq;
+using Newtonsoft.Json;
 using Xunit;
 
 using TransportType = Microsoft.AspNetCore.Sockets.TransportType;
@@ -32,7 +36,7 @@ namespace Microsoft.AspNetCore.SignalR.Client.Tests
             [Fact]
             public Task StartThrowsFormatExceptionIfNegotiationResponseHasNoTransports()
             {
-                return RunInvalidNegotiateResponseTest<FormatException>(ResponseUtils.CreateNegotiationContent(transportTypes: null), "No transports returned in negotiation response.");
+                return RunInvalidNegotiateResponseTest<InvalidOperationException>(ResponseUtils.CreateNegotiationContent(transportTypes: 0), "Unable to connect to the server with any of the available transports.");
             }
 
             [Theory]
@@ -67,12 +71,104 @@ namespace Microsoft.AspNetCore.SignalR.Client.Tests
                     CreateConnection(testHttpHandler, url: requestedUrl),
                     async (connection, closed) =>
                     {
-                        await connection.StartAsync().OrTimeout();
+                        await connection.StartAsync(TransferFormat.Text).OrTimeout();
                     });
 
                 Assert.Equal(expectedNegotiate, await negotiateUrlTcs.Task.OrTimeout());
             }
 
+            [Fact]
+            public async Task StartSkipsOverTransportsThatTheClientDoesNotUnderstand()
+            {
+                var testHttpHandler = new TestHttpMessageHandler(autoNegotiate: false);
+
+                testHttpHandler.OnLongPoll(cancellationToken => ResponseUtils.CreateResponse(HttpStatusCode.NoContent));
+                testHttpHandler.OnNegotiate((request, cancellationToken) =>
+                {
+                    return ResponseUtils.CreateResponse(HttpStatusCode.OK,
+                        JsonConvert.SerializeObject(new
+                        {
+                            connectionId = "00000000-0000-0000-0000-000000000000",
+                            availableTransports = new object[]
+                            {
+                                new
+                                {
+                                    transport = "QuantumEntanglement",
+                                    transferFormats = new string[] { "Qbits" },
+                                },
+                                new
+                                {
+                                    transport = "CarrierPigeon",
+                                    transferFormats = new string[] { "Text" },
+                                },
+                                new
+                                {
+                                    transport = "LongPolling",
+                                    transferFormats = new string[] { "Text", "Binary" }
+                                },
+                            }
+                        }));
+                });
+
+                var transportFactory = new Mock<ITransportFactory>(MockBehavior.Strict);
+
+                transportFactory.Setup(t => t.CreateTransport(TransportType.LongPolling))
+                    .Returns(new TestTransport(transferFormat: TransferFormat.Text | TransferFormat.Binary));
+
+                await WithConnectionAsync(
+                    CreateConnection(testHttpHandler, transportFactory: transportFactory.Object),
+                    async (connection, closed) =>
+                    {
+                        await connection.StartAsync(TransferFormat.Binary).OrTimeout();
+                    });
+            }
+
+            [Fact]
+            public async Task StartSkipsOverTransportsThatDoNotSupportTheRequredTransferFormat()
+            {
+                var testHttpHandler = new TestHttpMessageHandler(autoNegotiate: false);
+
+                testHttpHandler.OnLongPoll(cancellationToken => ResponseUtils.CreateResponse(HttpStatusCode.NoContent));
+                testHttpHandler.OnNegotiate((request, cancellationToken) =>
+                {
+                    return ResponseUtils.CreateResponse(HttpStatusCode.OK,
+                        JsonConvert.SerializeObject(new
+                        {
+                            connectionId = "00000000-0000-0000-0000-000000000000",
+                            availableTransports = new object[]
+                            {
+                                new
+                                {
+                                    transport = "WebSockets",
+                                    transferFormats = new string[] { "Qbits" },
+                                },
+                                new
+                                {
+                                    transport = "ServerSentEvents",
+                                    transferFormats = new string[] { "Text" },
+                                },
+                                new
+                                {
+                                    transport = "LongPolling",
+                                    transferFormats = new string[] { "Text", "Binary" }
+                                },
+                            }
+                        }));
+                });
+
+                var transportFactory = new Mock<ITransportFactory>(MockBehavior.Strict);
+
+                transportFactory.Setup(t => t.CreateTransport(TransportType.LongPolling))
+                    .Returns(new TestTransport(transferFormat: TransferFormat.Text | TransferFormat.Binary));
+
+                await WithConnectionAsync(
+                    CreateConnection(testHttpHandler, transportFactory: transportFactory.Object),
+                    async (connection, closed) =>
+                    {
+                        await connection.StartAsync(TransferFormat.Binary).OrTimeout();
+                    });
+            }
+
             private async Task RunInvalidNegotiateResponseTest<TException>(string negotiatePayload, string expectedExceptionMessage) where TException : Exception
             {
                 var testHttpHandler = new TestHttpMessageHandler(autoNegotiate: false);
@@ -84,7 +180,7 @@ namespace Microsoft.AspNetCore.SignalR.Client.Tests
                     async (connection, closed) =>
                     {
                         var exception = await Assert.ThrowsAsync<TException>(
-                            () => connection.StartAsync().OrTimeout());
+                            () => connection.StartAsync(TransferFormat.Text).OrTimeout());
 
                         Assert.Equal(expectedExceptionMessage, exception.Message);
                     });

test/Microsoft.AspNetCore.SignalR.Client.Tests/HttpConnectionTests.OnReceived.cs

@@ -6,6 +6,7 @@ using System.Net;
 using System.Text;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Client.Tests;
+using Microsoft.AspNetCore.Sockets;
 using Xunit;
 
 namespace Microsoft.AspNetCore.SignalR.Client.Tests
@@ -34,7 +35,7 @@ namespace Microsoft.AspNetCore.SignalR.Client.Tests
                             return Task.CompletedTask;
                         }, receiveTcs);
 
-                        await connection.StartAsync().OrTimeout();
+                        await connection.StartAsync(TransferFormat.Text).OrTimeout();
                         Assert.Contains("42", await receiveTcs.Task.OrTimeout());
                     });
             }
@@ -65,7 +66,7 @@ namespace Microsoft.AspNetCore.SignalR.Client.Tests
                             return Task.CompletedTask;
                         }, receiveTcs);
 
-                        await connection.StartAsync().OrTimeout();
+                        await connection.StartAsync(TransferFormat.Text).OrTimeout();
                         Assert.Contains("42", await receiveTcs.Task.OrTimeout());
                         Assert.True(receivedRaised);
                     });
@@ -97,7 +98,7 @@ namespace Microsoft.AspNetCore.SignalR.Client.Tests
                             return Task.CompletedTask;
                         }, receiveTcs);
 
-                        await connection.StartAsync().OrTimeout();
+                        await connection.StartAsync(TransferFormat.Text).OrTimeout();
                         Assert.Contains("42", await receiveTcs.Task.OrTimeout());
                         Assert.True(receivedRaised);
                     });

test/Microsoft.AspNetCore.SignalR.Client.Tests/HttpConnectionTests.SendAsync.cs

@@ -6,6 +6,7 @@ using System.Net;
 using System.Net.Http;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Client.Tests;
+using Microsoft.AspNetCore.Sockets;
 using Xunit;
 
 namespace Microsoft.AspNetCore.SignalR.Client.Tests
@@ -36,7 +37,7 @@ namespace Microsoft.AspNetCore.SignalR.Client.Tests
                     CreateConnection(testHttpHandler),
                     async (connection, closed) =>
                     {
-                        await connection.StartAsync().OrTimeout();
+                        await connection.StartAsync(TransferFormat.Text).OrTimeout();
 
                         await connection.SendAsync(data).OrTimeout();
 
@@ -66,7 +67,7 @@ namespace Microsoft.AspNetCore.SignalR.Client.Tests
                     CreateConnection(),
                     async (connection, closed) =>
                     {
-                        await connection.StartAsync().OrTimeout();
+                        await connection.StartAsync(TransferFormat.Text).OrTimeout();
                         await connection.StopAsync().OrTimeout();
 
                         var exception = await Assert.ThrowsAsync<InvalidOperationException>(
@@ -82,7 +83,7 @@ namespace Microsoft.AspNetCore.SignalR.Client.Tests
                     CreateConnection(),
                     async (connection, closed) =>
                     {
-                        await connection.StartAsync().OrTimeout();
+                        await connection.StartAsync(TransferFormat.Text).OrTimeout();
                         await connection.DisposeAsync().OrTimeout();
 
                         var exception = await Assert.ThrowsAsync<InvalidOperationException>(
@@ -114,7 +115,7 @@ namespace Microsoft.AspNetCore.SignalR.Client.Tests
                     CreateConnection(testHttpHandler),
                     async (connection, closed) =>
                     {
-                        await connection.StartAsync().OrTimeout();
+                        await connection.StartAsync(TransferFormat.Text).OrTimeout();
 
                         await connection.SendAsync(new byte[] { 0 }).OrTimeout();
 

test/Microsoft.AspNetCore.SignalR.Client.Tests/HttpConnectionTests.cs

@@ -67,7 +67,7 @@ namespace Microsoft.AspNetCore.SignalR.Client.Tests
                     var onReceived = new SyncPoint();
                     connection.OnReceived(_ => onReceived.WaitToContinue().OrTimeout());
 
-                    await connection.StartAsync().OrTimeout();
+                    await connection.StartAsync(TransferFormat.Text).OrTimeout();
 
                     // This will trigger the received callback
                     await testTransport.Application.Output.WriteAsync(new byte[] { 1 });
@@ -114,7 +114,7 @@ namespace Microsoft.AspNetCore.SignalR.Client.Tests
                         connection.OnReceived(_ => onReceived.WaitToContinue().OrTimeout());
 
                         logger.LogInformation("Starting connection");
-                        await connection.StartAsync().OrTimeout();
+                        await connection.StartAsync(TransferFormat.Text).OrTimeout();
                         logger.LogInformation("Started connection");
 
                         await testTransport.Application.Output.WriteAsync(new byte[] { 1 });
@@ -131,23 +131,6 @@ namespace Microsoft.AspNetCore.SignalR.Client.Tests
             }
         }
 
-        [Fact]
-        public async Task StartAsyncSetsTransferModeFeature()
-        {
-            var testTransport = new TestTransport(transferMode: TransferMode.Binary);
-            await WithConnectionAsync(
-                CreateConnection(transport: testTransport),
-                async (connection, closed) =>
-                {
-                    Assert.Null(connection.Features.Get<ITransferModeFeature>());
-                    await connection.StartAsync().OrTimeout();
-
-                    var transferModeFeature = connection.Features.Get<ITransferModeFeature>();
-                    Assert.NotNull(transferModeFeature);
-                    Assert.Equal(TransferMode.Binary, transferModeFeature.TransferMode);
-                });
-        }
-
         [Fact]
         public async Task HttpOptionsSetOntoHttpClientHandler()
         {
@@ -180,7 +163,7 @@ namespace Microsoft.AspNetCore.SignalR.Client.Tests
                 CreateConnection(httpOptions, url: "http://fakeuri.org/"),
                 async (connection, closed) =>
                 {
-                    await connection.StartAsync().OrTimeout();
+                    await connection.StartAsync(TransferFormat.Text).OrTimeout();
                 });
 
             Assert.NotNull(httpClientHandler);

test/Microsoft.AspNetCore.SignalR.Client.Tests/HubConnectionProtocolTests.cs

@@ -324,76 +324,10 @@ namespace Microsoft.AspNetCore.SignalR.Client.Tests
             }
         }
 
-        [Fact]
-        public async Task MessagesEncodedWhenUsingBinaryProtocolOverTextTransport()
-        {
-            var connection = new TestConnection(TransferMode.Text);
-
-            var hubConnection = new HubConnection(connection,
-                new MessagePackHubProtocol(), new LoggerFactory());
-            try
-            {
-                await hubConnection.StartAsync().OrTimeout();
-                await hubConnection.SendAsync("MyMethod", 42).OrTimeout();
-
-                await connection.ReadSentTextMessageAsync().OrTimeout();
-                var invokeMessage = await connection.ReadSentTextMessageAsync().OrTimeout();
-
-                // The message is in the following format `size:payload;`
-                var parts = invokeMessage.Split(':');
-                Assert.Equal(2, parts.Length);
-                Assert.True(int.TryParse(parts[0], out var payloadSize));
-                Assert.Equal(payloadSize, parts[1].Length - 1);
-                Assert.EndsWith(";", parts[1]);
-
-                // this throws if the message is not a valid base64 string
-                Convert.FromBase64String(parts[1].Substring(0, payloadSize));
-            }
-            finally
-            {
-                await hubConnection.DisposeAsync().OrTimeout();
-                await connection.DisposeAsync().OrTimeout();
-            }
-        }
-
-        [Fact]
-        public async Task MessagesDecodedWhenUsingBinaryProtocolOverTextTransport()
-        {
-            var connection = new TestConnection(TransferMode.Text);
-            var hubConnection = new HubConnection(connection,
-                new MessagePackHubProtocol(), new LoggerFactory());
-
-            var invocationTcs = new TaskCompletionSource<int>();
-            try
-            {
-                await hubConnection.StartAsync().OrTimeout();
-                hubConnection.On<int>("MyMethod", result => invocationTcs.SetResult(result));
-
-                using (var ms = new MemoryStream())
-                {
-                    new MessagePackHubProtocol()
-                        .WriteMessage(new InvocationMessage(null, "MyMethod", null, 42), ms);
-
-                    var invokeMessage = Convert.ToBase64String(ms.ToArray());
-                    var payloadSize = invokeMessage.Length.ToString(CultureInfo.InvariantCulture);
-                    var message = $"{payloadSize}:{invokeMessage};";
-
-                    connection.ReceivedMessages.TryWrite(Encoding.UTF8.GetBytes(message));
-                }
-
-                Assert.Equal(42, await invocationTcs.Task.OrTimeout());
-            }
-            finally
-            {
-                await hubConnection.DisposeAsync().OrTimeout();
-                await connection.DisposeAsync().OrTimeout();
-            }
-        }
-
         [Fact]
         public async Task AcceptsPingMessages()
         {
-            var connection = new TestConnection(TransferMode.Text);
+            var connection = new TestConnection();
             var hubConnection = new HubConnection(connection,
                 new JsonHubProtocol(), new LoggerFactory());
 

test/Microsoft.AspNetCore.SignalR.Client.Tests/HubConnectionTests.cs

@@ -8,6 +8,7 @@ using System.Threading.Tasks;
 using Microsoft.AspNetCore.Http.Features;
 using Microsoft.AspNetCore.SignalR.Internal;
 using Microsoft.AspNetCore.SignalR.Internal.Protocol;
+using Microsoft.AspNetCore.Sockets;
 using Microsoft.AspNetCore.Sockets.Client;
 using Microsoft.Extensions.Logging;
 using Moq;
@@ -21,12 +22,14 @@ namespace Microsoft.AspNetCore.SignalR.Client.Tests
         public async Task StartAsyncCallsConnectionStart()
         {
             var connection = new Mock<IConnection>();
+            var protocol = new Mock<IHubProtocol>();
+            protocol.SetupGet(p => p.TransferFormat).Returns(TransferFormat.Text);
             connection.SetupGet(p => p.Features).Returns(new FeatureCollection());
-            connection.Setup(m => m.StartAsync()).Returns(Task.CompletedTask).Verifiable();
+            connection.Setup(m => m.StartAsync(TransferFormat.Text)).Returns(Task.CompletedTask).Verifiable();
-            var hubConnection = new HubConnection(connection.Object, Mock.Of<IHubProtocol>(), null);
+            var hubConnection = new HubConnection(connection.Object, protocol.Object, null);
             await hubConnection.StartAsync();
 
-            connection.Verify(c => c.StartAsync(), Times.Once());
+            connection.Verify(c => c.StartAsync(TransferFormat.Text), Times.Once());
         }
 
         [Fact]
@@ -34,7 +37,7 @@ namespace Microsoft.AspNetCore.SignalR.Client.Tests
         {
             var connection = new Mock<IConnection>();
             connection.Setup(m => m.Features).Returns(new FeatureCollection());
-            connection.Setup(m => m.StartAsync()).Verifiable();
+            connection.Setup(m => m.StartAsync(TransferFormat.Text)).Verifiable();
             var hubConnection = new HubConnection(connection.Object, Mock.Of<IHubProtocol>(), null);
             await hubConnection.DisposeAsync();
 
@@ -249,7 +252,7 @@ namespace Microsoft.AspNetCore.SignalR.Client.Tests
 
             public string Name => "MockHubProtocol";
 
-            public ProtocolType Type => ProtocolType.Binary;
+            public TransferFormat TransferFormat => TransferFormat.Binary;
 
             public bool TryParseMessages(ReadOnlySpan<byte> input, IInvocationBinder binder, IList<HubMessage> messages)
             {

test/Microsoft.AspNetCore.SignalR.Client.Tests/LongPollingTransportTests.cs

@@ -46,7 +46,7 @@ namespace Microsoft.AspNetCore.Client.Tests
                 try
                 {
                     var pair = DuplexPipe.CreateConnectionPair(PipeOptions.Default, PipeOptions.Default);
-                    await longPollingTransport.StartAsync(new Uri("http://fakeuri.org"), pair.Application, TransferMode.Binary, connection: new TestConnection());
+                    await longPollingTransport.StartAsync(new Uri("http://fakeuri.org"), pair.Application, TransferFormat.Binary, connection: new TestConnection());
 
                     transportActiveTask = longPollingTransport.Running;
 
@@ -80,7 +80,7 @@ namespace Microsoft.AspNetCore.Client.Tests
                 try
                 {
                     var pair = DuplexPipe.CreateConnectionPair(PipeOptions.Default, PipeOptions.Default);
-                    await longPollingTransport.StartAsync(new Uri("http://fakeuri.org"), pair.Application, TransferMode.Binary, connection: new TestConnection());
+                    await longPollingTransport.StartAsync(new Uri("http://fakeuri.org"), pair.Application, TransferFormat.Binary, connection: new TestConnection());
 
                     await longPollingTransport.Running.OrTimeout();
 
@@ -134,7 +134,7 @@ namespace Microsoft.AspNetCore.Client.Tests
                 try
                 {
                     var pair = DuplexPipe.CreateConnectionPair(PipeOptions.Default, PipeOptions.Default);
-                    await longPollingTransport.StartAsync(new Uri("http://fakeuri.org"), pair.Application, TransferMode.Binary, connection: new TestConnection());
+                    await longPollingTransport.StartAsync(new Uri("http://fakeuri.org"), pair.Application, TransferFormat.Binary, connection: new TestConnection());
 
                     var data = await pair.Transport.Input.ReadAllAsync().OrTimeout();
                     await longPollingTransport.Running.OrTimeout();
@@ -165,7 +165,7 @@ namespace Microsoft.AspNetCore.Client.Tests
                 try
                 {
                     var pair = DuplexPipe.CreateConnectionPair(PipeOptions.Default, PipeOptions.Default);
-                    await longPollingTransport.StartAsync(new Uri("http://fakeuri.org"), pair.Application, TransferMode.Binary, connection: new TestConnection());
+                    await longPollingTransport.StartAsync(new Uri("http://fakeuri.org"), pair.Application, TransferFormat.Binary, connection: new TestConnection());
 
                     var exception =
                         await Assert.ThrowsAsync<HttpRequestException>(async () =>
@@ -207,7 +207,7 @@ namespace Microsoft.AspNetCore.Client.Tests
                 try
                 {
                     var pair = DuplexPipe.CreateConnectionPair(PipeOptions.Default, PipeOptions.Default);
-                    await longPollingTransport.StartAsync(new Uri("http://fakeuri.org"), pair.Application, TransferMode.Binary, connection: new TestConnection());
+                    await longPollingTransport.StartAsync(new Uri("http://fakeuri.org"), pair.Application, TransferFormat.Binary, connection: new TestConnection());
 
                     await pair.Transport.Output.WriteAsync(Encoding.UTF8.GetBytes("Hello World"));
 
@@ -241,7 +241,7 @@ namespace Microsoft.AspNetCore.Client.Tests
                 try
                 {
                     var pair = DuplexPipe.CreateConnectionPair(PipeOptions.Default, PipeOptions.Default);
-                    await longPollingTransport.StartAsync(new Uri("http://fakeuri.org"), pair.Application, TransferMode.Binary, connection: new TestConnection());
+                    await longPollingTransport.StartAsync(new Uri("http://fakeuri.org"), pair.Application, TransferFormat.Binary, connection: new TestConnection());
 
                     pair.Transport.Output.Complete();
 
@@ -289,7 +289,7 @@ namespace Microsoft.AspNetCore.Client.Tests
                     var pair = DuplexPipe.CreateConnectionPair(PipeOptions.Default, PipeOptions.Default);
 
                     // Start the transport
-                    await longPollingTransport.StartAsync(new Uri("http://fakeuri.org"), pair.Application, TransferMode.Binary, connection: new TestConnection());
+                    await longPollingTransport.StartAsync(new Uri("http://fakeuri.org"), pair.Application, TransferFormat.Binary, connection: new TestConnection());
 
                     // Wait for the transport to finish
                     await longPollingTransport.Running.OrTimeout();
@@ -341,7 +341,7 @@ namespace Microsoft.AspNetCore.Client.Tests
                     await pair.Transport.Output.WriteAsync(Encoding.UTF8.GetBytes("World"));
 
                     // Start the transport
-                    await longPollingTransport.StartAsync(new Uri("http://fakeuri.org"), pair.Application, TransferMode.Binary, connection: new TestConnection());
+                    await longPollingTransport.StartAsync(new Uri("http://fakeuri.org"), pair.Application, TransferFormat.Binary, connection: new TestConnection());
 
                     pair.Transport.Output.Complete();
 
@@ -360,9 +360,9 @@ namespace Microsoft.AspNetCore.Client.Tests
         }
 
         [Theory]
-        [InlineData(TransferMode.Binary)]
+        [InlineData(TransferFormat.Binary)]
-        [InlineData(TransferMode.Text)]
+        [InlineData(TransferFormat.Text)]
-        public async Task LongPollingTransportSetsTransferMode(TransferMode transferMode)
+        public async Task LongPollingTransportSetsTransferFormat(TransferFormat transferFormat)
         {
             var mockHttpHandler = new Mock<HttpMessageHandler>();
             mockHttpHandler.Protected()
@@ -381,9 +381,7 @@ namespace Microsoft.AspNetCore.Client.Tests
                 {
                     var pair = DuplexPipe.CreateConnectionPair(PipeOptions.Default, PipeOptions.Default);
 
-                    Assert.Null(longPollingTransport.Mode);
+                    await longPollingTransport.StartAsync(new Uri("http://fakeuri.org"), pair.Application, transferFormat, connection: new TestConnection());
-                    await longPollingTransport.StartAsync(new Uri("http://fakeuri.org"), pair.Application, transferMode, connection: new TestConnection());
-                    Assert.Equal(transferMode, longPollingTransport.Mode);
                 }
                 finally
                 {
@@ -415,8 +413,7 @@ namespace Microsoft.AspNetCore.Client.Tests
                 {
                     var pair = DuplexPipe.CreateConnectionPair(PipeOptions.Default, PipeOptions.Default);
 
-                    Assert.Null(longPollingTransport.Mode);
+                    await longPollingTransport.StartAsync(new Uri("http://fakeuri.org"), pair.Application, TransferFormat.Text, connection: new TestConnection());
-                    await longPollingTransport.StartAsync(new Uri("http://fakeuri.org"), pair.Application, TransferMode.Text, connection: new TestConnection());
                 }
                 finally
                 {
@@ -436,8 +433,10 @@ namespace Microsoft.AspNetCore.Client.Tests
             Assert.Equal(assemblyVersion.InformationalVersion, userAgentHeader.Product.Version);
         }
 
-        [Fact]
+        [Theory]
-        public async Task LongPollingTransportThrowsForInvalidTransferMode()
+        [InlineData(TransferFormat.Text | TransferFormat.Binary)] // Multiple values not allowed
+        [InlineData((TransferFormat)42)] // Unexpected value
+        public async Task LongPollingTransportThrowsForInvalidTransferFormat(TransferFormat transferFormat)
         {
             var mockHttpHandler = new Mock<HttpMessageHandler>();
             mockHttpHandler.Protected()
@@ -452,10 +451,10 @@ namespace Microsoft.AspNetCore.Client.Tests
             {
                 var longPollingTransport = new LongPollingTransport(httpClient);
                 var exception = await Assert.ThrowsAsync<ArgumentException>(() =>
-                    longPollingTransport.StartAsync(new Uri("http://fakeuri.org"), null, TransferMode.Text | TransferMode.Binary, connection: new TestConnection()));
+                    longPollingTransport.StartAsync(new Uri("http://fakeuri.org"), null, transferFormat, connection: new TestConnection()));
 
-                Assert.Contains("Invalid transfer mode.", exception.Message);
+                Assert.Contains($"The '{transferFormat}' transfer format is not supported by this transport.", exception.Message);
-                Assert.Equal("requestedTransferMode", exception.ParamName);
+                Assert.Equal("transferFormat", exception.ParamName);
             }
         }
 
@@ -488,7 +487,7 @@ namespace Microsoft.AspNetCore.Client.Tests
                 try
                 {
                     var pair = DuplexPipe.CreateConnectionPair(PipeOptions.Default, PipeOptions.Default);
-                    await longPollingTransport.StartAsync(new Uri("http://fakeuri.org"), pair.Application, TransferMode.Binary, connection: new TestConnection());
+                    await longPollingTransport.StartAsync(new Uri("http://fakeuri.org"), pair.Application, TransferFormat.Binary, connection: new TestConnection());
 
                     var completedTask = await Task.WhenAny(completionTcs.Task, longPollingTransport.Running).OrTimeout();
                     Assert.Equal(completionTcs.Task, completedTask);

test/Microsoft.AspNetCore.SignalR.Client.Tests/ResponseUtils.cs

@@ -2,10 +2,11 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
+using System.Collections.Generic;
 using System.Net;
 using System.Net.Http;
-using System.Text;
+using Microsoft.AspNetCore.Sockets;
-
+using Newtonsoft.Json;
 using SocketsTransportType = Microsoft.AspNetCore.Sockets.TransportType;
 
 namespace Microsoft.AspNetCore.Client.Tests
@@ -36,35 +37,36 @@ namespace Microsoft.AspNetCore.Client.Tests
         }
 
         public static string CreateNegotiationContent(string connectionId = "00000000-0000-0000-0000-000000000000",
-            SocketsTransportType? transportTypes = SocketsTransportType.All)
+            SocketsTransportType transportTypes = SocketsTransportType.All)
         {
-            var sb = new StringBuilder("{ ");
+            var availableTransports = new List<object>();
-            if (connectionId != null)
-            {
-                sb.Append($"\"connectionId\": \"{connectionId}\",");
-            }
-            if (transportTypes != null)
-            {
-                sb.Append($"\"availableTransports\": [ ");
-                if ((transportTypes & SocketsTransportType.WebSockets) == SocketsTransportType.WebSockets)
-                {
-                    sb.Append($"\"{nameof(SocketsTransportType.WebSockets)}\",");
-                }
-                if ((transportTypes & SocketsTransportType.ServerSentEvents) == SocketsTransportType.ServerSentEvents)
-                {
-                    sb.Append($"\"{nameof(SocketsTransportType.ServerSentEvents)}\",");
-                }
-                if ((transportTypes & SocketsTransportType.LongPolling) == SocketsTransportType.LongPolling)
-                {
-                    sb.Append($"\"{nameof(SocketsTransportType.LongPolling)}\",");
-                }
-                sb.Length--;
-                sb.Append("],");
-            }
-            sb.Length--;
-            sb.Append("}");
 
-            return sb.ToString();
+            if ((transportTypes & SocketsTransportType.WebSockets) != 0)
+            {
+                availableTransports.Add(new
+                {
+                    transport = nameof(SocketsTransportType.WebSockets),
+                    transferFormats = new[] { nameof(TransferFormat.Text), nameof(TransferFormat.Binary) }
+                });
+            }
+            if ((transportTypes & SocketsTransportType.ServerSentEvents) != 0)
+            {
+                availableTransports.Add(new
+                {
+                    transport = nameof(SocketsTransportType.ServerSentEvents),
+                    transferFormats = new[] { nameof(TransferFormat.Text) }
+                });
+            }
+            if ((transportTypes & SocketsTransportType.LongPolling) != 0)
+            {
+                availableTransports.Add(new
+                {
+                    transport = nameof(SocketsTransportType.LongPolling),
+                    transferFormats = new[] { nameof(TransferFormat.Text), nameof(TransferFormat.Binary) }
+                });
+            }
+
+            return JsonConvert.SerializeObject(new { connectionId, availableTransports });
         }
     }
 }

test/Microsoft.AspNetCore.SignalR.Client.Tests/ServerSentEventsTransportTests.cs

@@ -55,7 +55,7 @@ namespace Microsoft.AspNetCore.SignalR.Client.Tests
                     var sseTransport = new ServerSentEventsTransport(httpClient);
                     var pair = DuplexPipe.CreateConnectionPair(PipeOptions.Default, PipeOptions.Default);
                     await sseTransport.StartAsync(
-                        new Uri("http://fakeuri.org"), pair.Application, TransferMode.Text, connection: Mock.Of<IConnection>()).OrTimeout();
+                        new Uri("http://fakeuri.org"), pair.Application, TransferFormat.Text, connection: Mock.Of<IConnection>()).OrTimeout();
 
                     await eventStreamTcs.Task.OrTimeout();
                     await sseTransport.StopAsync().OrTimeout();
@@ -105,7 +105,7 @@ namespace Microsoft.AspNetCore.SignalR.Client.Tests
                     var pair = DuplexPipe.CreateConnectionPair(PipeOptions.Default, PipeOptions.Default);
 
                     await sseTransport.StartAsync(
-                        new Uri("http://fakeuri.org"), pair.Application, TransferMode.Text, connection: Mock.Of<IConnection>()).OrTimeout();
+                        new Uri("http://fakeuri.org"), pair.Application, TransferFormat.Text, connection: Mock.Of<IConnection>()).OrTimeout();
 
                     transportActiveTask = sseTransport.Running;
                     Assert.False(transportActiveTask.IsCompleted);
@@ -151,7 +151,7 @@ namespace Microsoft.AspNetCore.SignalR.Client.Tests
 
                 var pair = DuplexPipe.CreateConnectionPair(PipeOptions.Default, PipeOptions.Default);
                 await sseTransport.StartAsync(
-                    new Uri("http://fakeuri.org"), pair.Application, TransferMode.Text, connection: Mock.Of<IConnection>()).OrTimeout();
+                    new Uri("http://fakeuri.org"), pair.Application, TransferFormat.Text, connection: Mock.Of<IConnection>()).OrTimeout();
 
                 var exception = await Assert.ThrowsAsync<FormatException>(() => sseTransport.Running.OrTimeout());
                 Assert.Equal("Incomplete message.", exception.Message);
@@ -195,7 +195,7 @@ namespace Microsoft.AspNetCore.SignalR.Client.Tests
                 var pair = DuplexPipe.CreateConnectionPair(PipeOptions.Default, PipeOptions.Default);
 
                 await sseTransport.StartAsync(
-                    new Uri("http://fakeuri.org"), pair.Application, TransferMode.Text, connection: Mock.Of<IConnection>()).OrTimeout();
+                    new Uri("http://fakeuri.org"), pair.Application, TransferFormat.Text, connection: Mock.Of<IConnection>()).OrTimeout();
                 await eventStreamTcs.Task;
 
                 await pair.Transport.Output.WriteAsync(new byte[] { 0x42 });
@@ -239,7 +239,7 @@ namespace Microsoft.AspNetCore.SignalR.Client.Tests
                 var pair = DuplexPipe.CreateConnectionPair(PipeOptions.Default, PipeOptions.Default);
 
                 await sseTransport.StartAsync(
-                    new Uri("http://fakeuri.org"), pair.Application, TransferMode.Text, connection: Mock.Of<IConnection>()).OrTimeout();
+                    new Uri("http://fakeuri.org"), pair.Application, TransferFormat.Text, connection: Mock.Of<IConnection>()).OrTimeout();
                 await eventStreamTcs.Task.OrTimeout();
 
                 pair.Transport.Output.Complete();
@@ -267,7 +267,7 @@ namespace Microsoft.AspNetCore.SignalR.Client.Tests
                 var pair = DuplexPipe.CreateConnectionPair(PipeOptions.Default, PipeOptions.Default);
 
                 await sseTransport.StartAsync(
-                    new Uri("http://fakeuri.org"), pair.Application, TransferMode.Text, connection: Mock.Of<IConnection>()).OrTimeout();
+                    new Uri("http://fakeuri.org"), pair.Application, TransferFormat.Text, connection: Mock.Of<IConnection>()).OrTimeout();
 
                 var message = await pair.Transport.Input.ReadSingleAsync().OrTimeout();
                 Assert.Equal("3:abc", Encoding.ASCII.GetString(message));
@@ -276,10 +276,8 @@ namespace Microsoft.AspNetCore.SignalR.Client.Tests
             }
         }
 
-        [Theory]
+        [Fact]
-        [InlineData(TransferMode.Text)]
+        public async Task SSETransportDoesNotSupportBinary()
-        [InlineData(TransferMode.Binary)]
-        public async Task SSETransportSetsTransferMode(TransferMode transferMode)
         {
             var mockHttpHandler = new Mock<HttpMessageHandler>();
             mockHttpHandler.Protected()
@@ -293,12 +291,10 @@ namespace Microsoft.AspNetCore.SignalR.Client.Tests
             using (var httpClient = new HttpClient(mockHttpHandler.Object))
             {
                 var sseTransport = new ServerSentEventsTransport(httpClient);
-                Assert.Null(sseTransport.Mode);
 
                 var pair = DuplexPipe.CreateConnectionPair(PipeOptions.Default, PipeOptions.Default);
-                await sseTransport.StartAsync(new Uri("http://fakeuri.org"), pair.Application, transferMode, connection: Mock.Of<IConnection>()).OrTimeout();
+                var ex = await Assert.ThrowsAsync<ArgumentException>(() => sseTransport.StartAsync(new Uri("http://fakeuri.org"), pair.Application, TransferFormat.Binary, connection: Mock.Of<IConnection>()).OrTimeout());
-                Assert.Equal(TransferMode.Text, sseTransport.Mode);
+                Assert.Equal($"The 'Binary' transfer format is not supported by this transport.{Environment.NewLine}Parameter name: transferFormat", ex.Message);
-                await sseTransport.StopAsync().OrTimeout();
             }
         }
 
@@ -322,7 +318,7 @@ namespace Microsoft.AspNetCore.SignalR.Client.Tests
                 var sseTransport = new ServerSentEventsTransport(httpClient);
 
                 var pair = DuplexPipe.CreateConnectionPair(PipeOptions.Default, PipeOptions.Default);
-                await sseTransport.StartAsync(new Uri("http://fakeuri.org"), pair.Application, TransferMode.Text, connection: Mock.Of<IConnection>()).OrTimeout();
+                await sseTransport.StartAsync(new Uri("http://fakeuri.org"), pair.Application, TransferFormat.Text, connection: Mock.Of<IConnection>()).OrTimeout();
                 await sseTransport.StopAsync().OrTimeout();
             }
 
@@ -338,8 +334,11 @@ namespace Microsoft.AspNetCore.SignalR.Client.Tests
             Assert.Equal(assemblyVersion.InformationalVersion, userAgentHeader.Product.Version);
         }
 
-        [Fact]
+        [Theory]
-        public async Task SSETransportThrowsForInvalidTransferMode()
+        [InlineData(TransferFormat.Binary)] // Binary not supported
+        [InlineData(TransferFormat.Text | TransferFormat.Binary)] // Multiple values not allowed
+        [InlineData((TransferFormat)42)] // Unexpected value
+        public async Task SSETransportThrowsForInvalidTransferFormat(TransferFormat transferFormat)
         {
             var mockHttpHandler = new Mock<HttpMessageHandler>();
             mockHttpHandler.Protected()
@@ -354,10 +353,10 @@ namespace Microsoft.AspNetCore.SignalR.Client.Tests
             {
                 var sseTransport = new ServerSentEventsTransport(httpClient);
                 var exception = await Assert.ThrowsAsync<ArgumentException>(() =>
-                    sseTransport.StartAsync(new Uri("http://fakeuri.org"), null, TransferMode.Text | TransferMode.Binary, connection: Mock.Of<IConnection>()));
+                    sseTransport.StartAsync(new Uri("http://fakeuri.org"), null, transferFormat, connection: Mock.Of<IConnection>()));
 
-                Assert.Contains("Invalid transfer mode.", exception.Message);
+                Assert.Contains($"The '{transferFormat}' transfer format is not supported by this transport.", exception.Message);
-                Assert.Equal("requestedTransferMode", exception.ParamName);
+                Assert.Equal("transferFormat", exception.ParamName);
             }
         }
     }

test/Microsoft.AspNetCore.SignalR.Client.Tests/TestConnection.cs

@@ -29,8 +29,6 @@ namespace Microsoft.AspNetCore.SignalR.Client.Tests
         private CancellationTokenSource _receiveShutdownToken = new CancellationTokenSource();
         private Task _receiveLoop;
 
-        private TransferMode? _transferMode;
-
         public event Action<Exception> Closed;
         public Task Started => _started.Task;
         public Task Disposed => _disposed.Task;
@@ -44,9 +42,8 @@ namespace Microsoft.AspNetCore.SignalR.Client.Tests
 
         public IFeatureCollection Features { get; } = new FeatureCollection();
 
-        public TestConnection(TransferMode? transferMode = null)
+        public TestConnection()
         {
-            _transferMode = transferMode;
             _receiveLoop = ReceiveLoopAsync(_receiveShutdownToken.Token);
         }
 
@@ -80,20 +77,8 @@ namespace Microsoft.AspNetCore.SignalR.Client.Tests
             throw new ObjectDisposedException("Unable to send message, underlying channel was closed");
         }
 
-        public Task StartAsync()
+        public Task StartAsync(TransferFormat transferFormat)
         {
-            if (_transferMode.HasValue)
-            {
-                var transferModeFeature = Features.Get<ITransferModeFeature>();
-                if (transferModeFeature == null)
-                {
-                    transferModeFeature = new TransferModeFeature();
-                    Features.Set(transferModeFeature);
-                }
-
-                transferModeFeature.TransferMode = _transferMode.Value;
-            }
-
             _started.TrySetResult(null);
             return Task.CompletedTask;
         }

test/Microsoft.AspNetCore.SignalR.Client.Tests/TestTransport.cs

@@ -1,6 +1,5 @@
 using System;
 using System.IO.Pipelines;
-using System.Threading.Channels;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Sockets;
 using Microsoft.AspNetCore.Sockets.Client;
@@ -12,18 +11,22 @@ namespace Microsoft.AspNetCore.SignalR.Client.Tests
         private readonly Func<Task> _stopHandler;
         private readonly Func<Task> _startHandler;
 
-        public TransferMode? Mode { get; }
+        public TransferFormat? Format { get; }
         public IDuplexPipe Application { get; private set; }
 
-        public TestTransport(Func<Task> onTransportStop = null, Func<Task> onTransportStart = null, TransferMode transferMode = TransferMode.Text)
+        public TestTransport(Func<Task> onTransportStop = null, Func<Task> onTransportStart = null, TransferFormat transferFormat = TransferFormat.Text)
         {
             _stopHandler = onTransportStop ?? new Func<Task>(() => Task.CompletedTask);
             _startHandler = onTransportStart ?? new Func<Task>(() => Task.CompletedTask);
-            Mode = transferMode;
+            Format = transferFormat;
         }
 
-        public Task StartAsync(Uri url, IDuplexPipe application, TransferMode requestedTransferMode, IConnection connection)
+        public Task StartAsync(Uri url, IDuplexPipe application, TransferFormat transferFormat, IConnection connection)
         {
+            if ((Format & transferFormat) == 0)
+            {
+                throw new InvalidOperationException($"The '{transferFormat}' transfer format is not supported by this transport.");
+            }
             Application = application;
             return _startHandler();
         }

test/Microsoft.AspNetCore.SignalR.Common.Tests/Internal/Encoders/Base64EncoderTests.cs

@@ -1,59 +0,0 @@
-// Copyright (c) .NET Foundation. All rights reserved.
-// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
-
-using System;
-using System.Collections.Generic;
-using System.Text;
-using Xunit;
-
-namespace Microsoft.AspNetCore.SignalR.Internal.Encoders
-{
-    public class Base64EncoderTests
-    {
-        [Theory]
-        [MemberData(nameof(Payloads))]
-        public void VerifyDecode(string payload, string encoded)
-        {
-            var message = Encoding.UTF8.GetBytes(payload);
-            var encodedMessage = Encoding.UTF8.GetString(new Base64Encoder().Encode(message));
-            Assert.Equal(encoded, encodedMessage);
-        }
-
-        [Theory]
-        [MemberData(nameof(Payloads))]
-        public void VerifyEncode(string payload, string encoded)
-        {
-            ReadOnlySpan<byte> encodedMessage = Encoding.UTF8.GetBytes(encoded);
-            var encoder = new Base64Encoder();
-            encoder.TryDecode(ref encodedMessage, out var data);
-            var decodedMessage = Encoding.UTF8.GetString(data.ToArray());
-            Assert.Equal(payload, decodedMessage);
-        }
-
-        [Fact]
-        public void CanParseMultipleMessages()
-        {
-            ReadOnlySpan<byte> data = Encoding.UTF8.GetBytes("28:QQpSDUMNCjtERUYxMjM0NTY3ODkw;4:QUJD;4:QUJD;");
-            var encoder = new Base64Encoder();
-            Assert.True(encoder.TryDecode(ref data, out var payload1));
-            Assert.True(encoder.TryDecode(ref data, out var payload2));
-            Assert.True(encoder.TryDecode(ref data, out var payload3));
-            Assert.False(encoder.TryDecode(ref data, out var payload4));
-            Assert.Equal(0, data.Length);
-            var payload1Value = Encoding.UTF8.GetString(payload1.ToArray());
-            var payload2Value = Encoding.UTF8.GetString(payload2.ToArray());
-            var payload3Value = Encoding.UTF8.GetString(payload3.ToArray());
-            Assert.Equal("A\nR\rC\r\n;DEF1234567890", payload1Value);
-            Assert.Equal("ABC", payload2Value);
-            Assert.Equal("ABC", payload3Value);
-        }
-
-        public static IEnumerable<object[]> Payloads =>
-            new object[][]
-            {
-                new object[] { "", "0:;" },
-                new object[] { "ABC", "4:QUJD;" },
-                new object[] { "A\nR\rC\r\n;DEF1234567890", "28:QQpSDUMNCjtERUYxMjM0NTY3ODkw;" },
-            };
-    }
-}

test/Microsoft.AspNetCore.SignalR.Common.Tests/Internal/Encoders/LengthPrefixedTextMessageParserTests.cs

@@ -1,90 +0,0 @@
-// Copyright (c) .NET Foundation. All rights reserved.
-// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
-
-using System;
-using System.Collections.Generic;
-using System.Text;
-using Microsoft.AspNetCore.SignalR.Internal.Encoders;
-using Xunit;
-
-namespace Microsoft.AspNetCore.SignalR.Common.Tests.Internal.Encoders
-{
-    public class LengthPrefixedTextMessageParserTests
-    {
-        [Theory]
-        [InlineData("0:;", "")]
-        [InlineData("3:ABC;", "ABC")]
-        [InlineData("11:A\nR\rC\r\n;DEF;", "A\nR\rC\r\n;DEF")]
-        [InlineData("12:Hello, World;", "Hello, World")]
-        public void ReadTextMessage(string encoded, string payload)
-        {
-            ReadOnlySpan<byte> buffer = Encoding.UTF8.GetBytes(encoded);
-
-            Assert.True(LengthPrefixedTextMessageParser.TryParseMessage(ref buffer, out var message));
-            Assert.Equal(0, buffer.Length);
-            Assert.Equal(Encoding.UTF8.GetBytes(payload), message.ToArray());
-        }
-
-        [Fact]
-        public void ReadMultipleMessages()
-        {
-            const string encoded = "0:;14:Hello,\r\nWorld!;";
-            ReadOnlySpan<byte> buffer = Encoding.UTF8.GetBytes(encoded);
-
-            var messages = new List<byte[]>();
-            while (LengthPrefixedTextMessageParser.TryParseMessage(ref buffer, out var message))
-            {
-                messages.Add(message.ToArray());
-            }
-
-            Assert.Equal(0, buffer.Length);
-
-            Assert.Equal(2, messages.Count);
-            Assert.Equal(new byte[0], messages[0]);
-            Assert.Equal(Encoding.UTF8.GetBytes("Hello,\r\nWorld!"), messages[1]);
-        }
-
-        [Theory]
-        [InlineData("")]
-        [InlineData("ABC")]
-        [InlineData("1230450945")]
-        [InlineData("1:")]
-        [InlineData("10")]
-        [InlineData("5:A")]
-        [InlineData("5:ABCDE")]
-        public void ReadIncompleteMessages(string encoded)
-        {
-            ReadOnlySpan<byte> buffer = Encoding.UTF8.GetBytes(encoded);
-            Assert.False(LengthPrefixedTextMessageParser.TryParseMessage(ref buffer, out _));
-        }
-
-        [Theory]
-        [InlineData("X:", "Invalid length: 'X'")]
-        [InlineData("1:asdf", "Missing delimiter ';' after payload")]
-        [InlineData("1029348109238412903849023841290834901283409128349018239048102394:ABCDEF", "Invalid length: '1029348109238412903849023841290834901283409128349018239048102394'")]
-        [InlineData("12ab34:", "Invalid length: '12ab34'")]
-        [InlineData("5:ABCDEF", "Missing delimiter ';' after payload")]
-        public void ReadInvalidMessages(string encoded, string expectedMessage)
-        {
-            var ex = Assert.Throws<FormatException>(() =>
-            {
-                ReadOnlySpan<byte> buffer = Encoding.UTF8.GetBytes(encoded);
-                LengthPrefixedTextMessageParser.TryParseMessage(ref buffer, out _);
-            });
-            Assert.Equal(expectedMessage, ex.Message);
-        }
-
-        [Fact]
-        public void ReadInvalidEncodedMessage()
-        {
-            var ex = Assert.Throws<FormatException>(() =>
-            {
-                // Invalid because first character is a UTF-8 "continuation" character
-                // We need to include the ':' so that
-                ReadOnlySpan<byte> buffer = new byte[] { 0x48, 0x65, 0x80, 0x6C, 0x6F, (byte)':' };
-                LengthPrefixedTextMessageParser.TryParseMessage(ref buffer, out _);
-            });
-            Assert.Equal("Invalid length: 'He<48>lo'", ex.Message);
-        }
-    }
-}

test/Microsoft.AspNetCore.SignalR.Redis.Tests/RedisEndToEnd.cs

@@ -112,7 +112,11 @@ namespace Microsoft.AspNetCore.SignalR.Redis.Tests
                 foreach (var transport in TransportTypes())
                 {
                     yield return new object[] { transport, new JsonHubProtocol() };
-                    yield return new object[] { transport, new MessagePackHubProtocol() };
+
+                    if (transport != TransportType.ServerSentEvents)
+                    {
+                        yield return new object[] { transport, new MessagePackHubProtocol() };
+                    }
                 }
             }
         }

test/Microsoft.AspNetCore.SignalR.Tests.Utils/HubConnectionContextUtils.cs

@@ -3,7 +3,6 @@
 
 using System;
 using Microsoft.AspNetCore.SignalR.Internal;
-using Microsoft.AspNetCore.SignalR.Internal.Encoders;
 using Microsoft.AspNetCore.SignalR.Internal.Protocol;
 using Microsoft.AspNetCore.Sockets;
 using Microsoft.Extensions.Logging.Abstractions;
@@ -17,15 +16,15 @@ namespace Microsoft.AspNetCore.SignalR.Tests
         {
             return new HubConnectionContext(connection, TimeSpan.FromSeconds(15), NullLoggerFactory.Instance)
             {
-                ProtocolReaderWriter = new HubProtocolReaderWriter(new JsonHubProtocol(), new PassThroughEncoder())
+                Protocol = new JsonHubProtocol()
             };
         }
 
         public static Mock<HubConnectionContext> CreateMock(DefaultConnectionContext connection)
         {
             var mock = new Mock<HubConnectionContext>(connection, TimeSpan.FromSeconds(15), NullLoggerFactory.Instance) { CallBase = true };
-            var readerWriter = new HubProtocolReaderWriter(new JsonHubProtocol(), new PassThroughEncoder());
+            var protocol = new JsonHubProtocol();
-            mock.SetupGet(m => m.ProtocolReaderWriter).Returns(readerWriter);
+            mock.SetupGet(m => m.Protocol).Returns(protocol);
             return mock;
 
         }

test/Microsoft.AspNetCore.SignalR.Tests.Utils/TestClient.cs

@@ -2,6 +2,7 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
+using System.Buffers;
 using System.Collections.Generic;
 using System.IO;
 using System.IO.Pipelines;
@@ -9,7 +10,6 @@ using System.Security.Claims;
 using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.SignalR.Internal;
-using Microsoft.AspNetCore.SignalR.Internal.Encoders;
 using Microsoft.AspNetCore.SignalR.Internal.Protocol;
 using Microsoft.AspNetCore.Sockets;
 
@@ -18,7 +18,7 @@ namespace Microsoft.AspNetCore.SignalR.Tests
     public class TestClient : IDisposable
     {
         private static int _id;
-        private readonly HubProtocolReaderWriter _protocolReaderWriter;
+        private readonly IHubProtocol _protocol;
         private readonly IInvocationBinder _invocationBinder;
         private CancellationTokenSource _cts;
         private Queue<HubMessage> _messages = new Queue<HubMessage>();
@@ -26,7 +26,7 @@ namespace Microsoft.AspNetCore.SignalR.Tests
         public DefaultConnectionContext Connection { get; }
         public Task Connected => ((TaskCompletionSource<bool>)Connection.Metadata["ConnectedTask"]).Task;
 
-        public TestClient(bool synchronousCallbacks = false, IHubProtocol protocol = null, IDataEncoder dataEncoder = null, IInvocationBinder invocationBinder = null, bool addClaimId = false)
+        public TestClient(bool synchronousCallbacks = false, IHubProtocol protocol = null, IInvocationBinder invocationBinder = null, bool addClaimId = false)
         {
             var options = new PipeOptions(readerScheduler: synchronousCallbacks ? PipeScheduler.Inline : null);
             var pair = DuplexPipe.CreateConnectionPair(options, options);
@@ -42,16 +42,14 @@ namespace Microsoft.AspNetCore.SignalR.Tests
             Connection.User = new ClaimsPrincipal(new ClaimsIdentity(claims));
             Connection.Metadata["ConnectedTask"] = new TaskCompletionSource<bool>();
 
-            protocol = protocol ?? new JsonHubProtocol();
+            _protocol = protocol ?? new JsonHubProtocol();
-            dataEncoder = dataEncoder ?? new PassThroughEncoder();
-            _protocolReaderWriter = new HubProtocolReaderWriter(protocol, dataEncoder);
             _invocationBinder = invocationBinder ?? new DefaultInvocationBinder();
 
             _cts = new CancellationTokenSource();
 
             using (var memoryStream = new MemoryStream())
             {
-                NegotiationProtocol.WriteMessage(new NegotiationMessage(protocol.Name), memoryStream);
+                NegotiationProtocol.WriteMessage(new NegotiationMessage(_protocol.Name), memoryStream);
                 Connection.Application.Output.WriteAsync(memoryStream.ToArray());
             }
         }
@@ -143,7 +141,8 @@ namespace Microsoft.AspNetCore.SignalR.Tests
 
         public async Task<string> SendHubMessageAsync(HubMessage message)
         {
-            var payload = _protocolReaderWriter.WriteMessage(message);
+            var payload = _protocol.WriteToArray(message);
+
             await Connection.Application.Output.WriteAsync(payload);
             return message is HubInvocationMessage hubMessage ? hubMessage.InvocationId : null;
         }
@@ -201,7 +200,8 @@ namespace Microsoft.AspNetCore.SignalR.Tests
 
             try
             {
-                if (_protocolReaderWriter.ReadMessages(result.Buffer, _invocationBinder, out var messages, out consumed, out examined))
+                var messages = new List<HubMessage>();
+                if (_protocol.TryParseMessages(result.Buffer.ToArray(), _invocationBinder, messages))
                 {
                     foreach (var m in messages)
                     {

test/Microsoft.AspNetCore.SignalR.Tests/EndToEndTests.cs

@@ -53,7 +53,7 @@ namespace Microsoft.AspNetCore.SignalR.Tests
             // The test should connect to the server using WebSockets transport on Windows 8 and newer.
             // On Windows 7/2008R2 it should use ServerSentEvents transport to connect to the server.
             var connection = new HttpConnection(new Uri(url));
-            await connection.StartAsync().OrTimeout();
+            await connection.StartAsync(TransferFormat.Binary).OrTimeout();
             await connection.DisposeAsync().OrTimeout();
         }
 
@@ -66,7 +66,7 @@ namespace Microsoft.AspNetCore.SignalR.Tests
 
             // The test logic lives in the TestTransportFactory and FakeTransport.
             var connection = new HttpConnection(new Uri(url), new TestTransportFactory(), null, null);
-            await connection.StartAsync().OrTimeout();
+            await connection.StartAsync(TransferFormat.Text).OrTimeout();
             await connection.DisposeAsync().OrTimeout();
         }
 
@@ -76,7 +76,7 @@ namespace Microsoft.AspNetCore.SignalR.Tests
         {
             var url = _serverFixture.Url + "/echo";
             var connection = new HttpConnection(new Uri(url), transportType);
-            await connection.StartAsync().OrTimeout();
+            await connection.StartAsync(TransferFormat.Text).OrTimeout();
             await connection.DisposeAsync().OrTimeout();
         }
 
@@ -145,7 +145,7 @@ namespace Microsoft.AspNetCore.SignalR.Tests
                     }, receiveTcs);
 
                     var message = new byte[] { 42 };
-                    await connection.StartAsync().OrTimeout();
+                    await connection.StartAsync(TransferFormat.Binary).OrTimeout();
                     await connection.SendAsync(message).OrTimeout();
 
                     var receivedData = await receiveTcs.Task.OrTimeout();
@@ -166,8 +166,8 @@ namespace Microsoft.AspNetCore.SignalR.Tests
         }
 
         [Theory(Skip = "https://github.com/aspnet/SignalR/issues/1485")]
-        [MemberData(nameof(TransportTypesAndTransferModes))]
+        [MemberData(nameof(TransportTypesAndTransferFormats))]
-        public async Task ConnectionCanSendAndReceiveMessages(TransportType transportType, TransferMode requestedTransferMode)
+        public async Task ConnectionCanSendAndReceiveMessages(TransportType transportType, TransferFormat requestedTransferFormat)
         {
             using (StartLog(out var loggerFactory, testName: $"ConnectionCanSendAndReceiveMessages_{transportType.ToString()}"))
             {
@@ -177,9 +177,6 @@ namespace Microsoft.AspNetCore.SignalR.Tests
 
                 var url = _serverFixture.Url + "/echo";
                 var connection = new HttpConnection(new Uri(url), transportType, loggerFactory);
-
-                connection.Features.Set<ITransferModeFeature>(
-                    new TransferModeFeature { TransferMode = requestedTransferMode });
                 try
                 {
                     var closeTcs = new TaskCompletionSource<object>();
@@ -199,28 +196,17 @@ namespace Microsoft.AspNetCore.SignalR.Tests
                     connection.OnReceived((data, state) =>
                     {
                         logger.LogInformation("Received {length} byte message", data.Length);
-
-                        if (IsBase64Encoded(requestedTransferMode, connection))
-                        {
-                            data = Convert.FromBase64String(Encoding.UTF8.GetString(data));
-                        }
                         var tcs = (TaskCompletionSource<string>)state;
                         tcs.TrySetResult(Encoding.UTF8.GetString(data));
                         return Task.CompletedTask;
                     }, receiveTcs);
 
                     logger.LogInformation("Starting connection to {url}", url);
-                    await connection.StartAsync().OrTimeout();
+                    await connection.StartAsync(requestedTransferFormat).OrTimeout();
                     logger.LogInformation("Started connection to {url}", url);
 
                     var bytes = Encoding.UTF8.GetBytes(message);
 
-                    // Need to encode binary payloads sent over text transports
-                    if (IsBase64Encoded(requestedTransferMode, connection))
-                    {
-                        bytes = Encoding.UTF8.GetBytes(Convert.ToBase64String(bytes));
-                    }
-
                     logger.LogInformation("Sending {length} byte message", bytes.Length);
                     try
                     {
@@ -255,12 +241,6 @@ namespace Microsoft.AspNetCore.SignalR.Tests
             }
         }
 
-        private bool IsBase64Encoded(TransferMode transferMode, IConnection connection)
-        {
-            return transferMode == TransferMode.Binary &&
-                connection.Features.Get<ITransferModeFeature>().TransferMode == TransferMode.Text;
-        }
-
         public static IEnumerable<object[]> MessageSizesData
         {
             get
@@ -281,8 +261,6 @@ namespace Microsoft.AspNetCore.SignalR.Tests
 
                 var url = _serverFixture.Url + "/echo";
                 var connection = new HttpConnection(new Uri(url), TransportType.WebSockets, loggerFactory);
-                connection.Features.Set<ITransferModeFeature>(
-                    new TransferModeFeature { TransferMode = TransferMode.Binary });
 
                 try
                 {
@@ -296,7 +274,7 @@ namespace Microsoft.AspNetCore.SignalR.Tests
                     }, receiveTcs);
 
                     logger.LogInformation("Starting connection to {url}", url);
-                    await connection.StartAsync().OrTimeout();
+                    await connection.StartAsync(TransferFormat.Binary).OrTimeout();
                     logger.LogInformation("Started connection to {url}", url);
 
                     var bytes = Encoding.UTF8.GetBytes(message);
@@ -416,16 +394,15 @@ namespace Microsoft.AspNetCore.SignalR.Tests
 
         private class FakeTransport : ITransport
         {
-            public TransferMode? Mode => TransferMode.Text;
             public string prevConnectionId = null;
             private int tries = 0;
             private IDuplexPipe _application;
 
-            public Task StartAsync(Uri url, IDuplexPipe application, TransferMode requestedTransferMode, IConnection connection)
+            public Task StartAsync(Uri url, IDuplexPipe application, TransferFormat transferFormat, IConnection connection)
             {
                 _application = application;
                 tries++;
-                Assert.True(QueryHelpers.ParseQuery(url.Query.ToString()).TryGetValue("id", out var id)); 
+                Assert.True(QueryHelpers.ParseQuery(url.Query.ToString()).TryGetValue("id", out var id));
                 if (prevConnectionId == null)
                 {
                     prevConnectionId = id;
@@ -467,14 +444,18 @@ namespace Microsoft.AspNetCore.SignalR.Tests
             }
         }
 
-        public static IEnumerable<object[]> TransportTypesAndTransferModes
+        public static IEnumerable<object[]> TransportTypesAndTransferFormats
         {
             get
             {
                 foreach (var transport in TransportTypes)
                 {
-                    yield return new object[] { transport[0], TransferMode.Text };
+                    yield return new object[] { transport[0], TransferFormat.Text };
-                    yield return new object[] { transport[0], TransferMode.Binary };
+
+                    if ((TransportType)transport[0] != TransportType.ServerSentEvents)
+                    {
+                        yield return new object[] { transport[0], TransferFormat.Binary };
+                    }
                 }
             }
         }

test/Microsoft.AspNetCore.SignalR.Tests/HubEndpointTests.cs

@@ -9,7 +9,6 @@ using System.Security.Claims;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Http;
 using Microsoft.AspNetCore.SignalR.Internal;
-using Microsoft.AspNetCore.SignalR.Internal.Encoders;
 using Microsoft.AspNetCore.SignalR.Internal.Protocol;
 using Microsoft.AspNetCore.SignalR.Tests.HubEndpointTestUtils;
 using Microsoft.AspNetCore.Sockets;
@@ -1333,10 +1332,7 @@ namespace Microsoft.AspNetCore.SignalR.Tests
 
             using (var client = new TestClient(synchronousCallbacks: false, protocol: protocol, invocationBinder: invocationBinder.Object))
             {
-                var transportFeature = new Mock<IConnectionTransportFeature>();
+                client.Connection.SupportedFormats = protocol.TransferFormat;
-                transportFeature.SetupGet(f => f.TransportCapabilities)
-                    .Returns(protocol.Type == ProtocolType.Binary ? TransferMode.Binary : TransferMode.Text);
-                client.Connection.Features.Set(transportFeature.Object);
 
                 var endPointLifetime = endPoint.OnConnectedAsync(client.Connection);
 
@@ -1419,7 +1415,7 @@ namespace Microsoft.AspNetCore.SignalR.Tests
             var endPoint = serviceProvider.GetService<HubEndPoint<MethodHub>>();
 
             using (var client1 = new TestClient(protocol: new JsonHubProtocol()))
-            using (var client2 = new TestClient(protocol: new MessagePackHubProtocol(), dataEncoder: new Base64Encoder()))
+            using (var client2 = new TestClient(protocol: new MessagePackHubProtocol()))
             {
                 var endPointLifetime1 = endPoint.OnConnectedAsync(client1.Connection);
                 var endPointLifetime2 = endPoint.OnConnectedAsync(client2.Connection);
@@ -1617,9 +1613,7 @@ namespace Microsoft.AspNetCore.SignalR.Tests
             var msgPackOptions = serviceProvider.GetRequiredService<IOptions<MessagePackHubProtocolOptions>>();
             using (var client = new TestClient(synchronousCallbacks: false, protocol: new MessagePackHubProtocol(msgPackOptions)))
             {
-                var transportFeature = new Mock<IConnectionTransportFeature>();
+                client.Connection.SupportedFormats = TransferFormat.Binary;
-                transportFeature.SetupGet(f => f.TransportCapabilities).Returns(TransferMode.Binary);
-                client.Connection.Features.Set(transportFeature.Object);
                 var endPointLifetime = endPoint.OnConnectedAsync(client.Connection);
 
                 await client.Connected.OrTimeout();
@@ -1792,6 +1786,21 @@ namespace Microsoft.AspNetCore.SignalR.Tests
             }
         }
 
+        [Fact]
+        public async Task NegotiatingFailsIfMsgPackRequestedOverTextOnlyTransport()
+        {
+            var serviceProvider = HubEndPointTestUtils.CreateServiceProvider(services =>
+                services.Configure<HubOptions>(options =>
+                    options.KeepAliveInterval = TimeSpan.FromMilliseconds(100)));
+            var endPoint = serviceProvider.GetService<HubEndPoint<MethodHub>>();
+
+            using (var client = new TestClient(false, new MessagePackHubProtocol()))
+            {
+                client.Connection.SupportedFormats = TransferFormat.Text;
+                var ex = await Assert.ThrowsAsync<InvalidOperationException>(() => endPoint.OnConnectedAsync(client.Connection).OrTimeout());
+            }
+        }
+
         public static IEnumerable<object[]> HubTypes()
         {
             yield return new[] { typeof(DynamicTestHub) };

test/Microsoft.AspNetCore.SignalR.Tests/WebSocketsTransportTests.cs

@@ -76,7 +76,7 @@ namespace Microsoft.AspNetCore.SignalR.Tests
                 var pair = DuplexPipe.CreateConnectionPair(PipeOptions.Default, PipeOptions.Default);
                 var webSocketsTransport = new WebSocketsTransport(httpOptions: null, loggerFactory: loggerFactory);
                 await webSocketsTransport.StartAsync(new Uri(_serverFixture.WebSocketsUrl + "/echo"), pair.Application,
-                    TransferMode.Binary, connection: Mock.Of<IConnection>()).OrTimeout();
+                    TransferFormat.Binary, connection: Mock.Of<IConnection>()).OrTimeout();
                 await webSocketsTransport.StopAsync().OrTimeout();
                 await webSocketsTransport.Running.OrTimeout();
             }
@@ -91,7 +91,7 @@ namespace Microsoft.AspNetCore.SignalR.Tests
                 var pair = DuplexPipe.CreateConnectionPair(PipeOptions.Default, PipeOptions.Default);
                 var webSocketsTransport = new WebSocketsTransport(httpOptions: null, loggerFactory: loggerFactory);
                 await webSocketsTransport.StartAsync(new Uri(_serverFixture.WebSocketsUrl + "/httpheader"), pair.Application,
-                    TransferMode.Binary, connection: Mock.Of<IConnection>()).OrTimeout();
+                    TransferFormat.Binary, connection: Mock.Of<IConnection>()).OrTimeout();
 
                 await pair.Transport.Output.WriteAsync(Encoding.UTF8.GetBytes("User-Agent"));
 
@@ -120,7 +120,7 @@ namespace Microsoft.AspNetCore.SignalR.Tests
                 var pair = DuplexPipe.CreateConnectionPair(PipeOptions.Default, PipeOptions.Default);
                 var webSocketsTransport = new WebSocketsTransport(httpOptions: null, loggerFactory: loggerFactory);
                 await webSocketsTransport.StartAsync(new Uri(_serverFixture.WebSocketsUrl + "/echo"), pair.Application,
-                    TransferMode.Binary, connection: Mock.Of<IConnection>());
+                    TransferFormat.Binary, connection: Mock.Of<IConnection>());
                 pair.Transport.Output.Complete();
                 await webSocketsTransport.Running.OrTimeout(TimeSpan.FromSeconds(10));
             }
@@ -128,15 +128,15 @@ namespace Microsoft.AspNetCore.SignalR.Tests
 
         [ConditionalTheory]
         [OSSkipCondition(OperatingSystems.Windows, WindowsVersions.Win7, WindowsVersions.Win2008R2, SkipReason = "No WebSockets Client for this platform")]
-        [InlineData(TransferMode.Text)]
+        [InlineData(TransferFormat.Text)]
-        [InlineData(TransferMode.Binary)]
+        [InlineData(TransferFormat.Binary)]
-        public async Task WebSocketsTransportStopsWhenConnectionClosedByTheServer(TransferMode transferMode)
+        public async Task WebSocketsTransportStopsWhenConnectionClosedByTheServer(TransferFormat transferFormat)
         {
             using (StartLog(out var loggerFactory))
             {
                 var pair = DuplexPipe.CreateConnectionPair(PipeOptions.Default, PipeOptions.Default);
                 var webSocketsTransport = new WebSocketsTransport(httpOptions: null, loggerFactory: loggerFactory);
-                await webSocketsTransport.StartAsync(new Uri(_serverFixture.WebSocketsUrl + "/echo"), pair.Application, transferMode, connection: Mock.Of<IConnection>());
+                await webSocketsTransport.StartAsync(new Uri(_serverFixture.WebSocketsUrl + "/echo"), pair.Application, transferFormat, connection: Mock.Of<IConnection>());
 
                 await pair.Transport.Output.WriteAsync(new byte[] { 0x42 });
 
@@ -151,38 +151,38 @@ namespace Microsoft.AspNetCore.SignalR.Tests
 
         [ConditionalTheory]
         [OSSkipCondition(OperatingSystems.Windows, WindowsVersions.Win7, WindowsVersions.Win2008R2, SkipReason = "No WebSockets Client for this platform")]
-        [InlineData(TransferMode.Text)]
+        [InlineData(TransferFormat.Text)]
-        [InlineData(TransferMode.Binary)]
+        [InlineData(TransferFormat.Binary)]
-        public async Task WebSocketsTransportSetsTransferMode(TransferMode transferMode)
+        public async Task WebSocketsTransportSetsTransferFormat(TransferFormat transferFormat)
         {
             using (StartLog(out var loggerFactory))
             {
                 var pair = DuplexPipe.CreateConnectionPair(PipeOptions.Default, PipeOptions.Default);
                 var webSocketsTransport = new WebSocketsTransport(httpOptions: null, loggerFactory: loggerFactory);
 
-                Assert.Null(webSocketsTransport.Mode);
                 await webSocketsTransport.StartAsync(new Uri(_serverFixture.WebSocketsUrl + "/echo"), pair.Application,
-                    transferMode, connection: Mock.Of<IConnection>()).OrTimeout();
+                    transferFormat, connection: Mock.Of<IConnection>()).OrTimeout();
-                Assert.Equal(transferMode, webSocketsTransport.Mode);
 
                 await webSocketsTransport.StopAsync().OrTimeout();
                 await webSocketsTransport.Running.OrTimeout();
             }
         }
 
-        [ConditionalFact]
+        [ConditionalTheory]
+        [InlineData(TransferFormat.Text | TransferFormat.Binary)] // Multiple values not allowed
+        [InlineData((TransferFormat)42)] // Unexpected value
         [OSSkipCondition(OperatingSystems.Windows, WindowsVersions.Win7, WindowsVersions.Win2008R2, SkipReason = "No WebSockets Client for this platform")]
-        public async Task WebSocketsTransportThrowsForInvalidTransferMode()
+        public async Task WebSocketsTransportThrowsForInvalidTransferFormat(TransferFormat transferFormat)
         {
             using (StartLog(out var loggerFactory))
             {
                 var pair = DuplexPipe.CreateConnectionPair(PipeOptions.Default, PipeOptions.Default);
                 var webSocketsTransport = new WebSocketsTransport(httpOptions: null, loggerFactory: loggerFactory);
                 var exception = await Assert.ThrowsAsync<ArgumentException>(() =>
-                    webSocketsTransport.StartAsync(new Uri("http://fakeuri.org"), pair.Application, TransferMode.Text | TransferMode.Binary, connection: Mock.Of<IConnection>()));
+                    webSocketsTransport.StartAsync(new Uri("http://fakeuri.org"), pair.Application, transferFormat, connection: Mock.Of<IConnection>()));
 
-                Assert.Contains("Invalid transfer mode.", exception.Message);
+                Assert.Contains($"The '{transferFormat}' transfer format is not supported by this transport.", exception.Message);
-                Assert.Equal("requestedTransferMode", exception.ParamName);
+                Assert.Equal("transferFormat", exception.ParamName);
             }
         }
     }

test/Microsoft.AspNetCore.Sockets.Tests/HttpConnectionDispatcherTests.cs

@@ -146,7 +146,7 @@ namespace Microsoft.AspNetCore.Sockets.Tests
         [InlineData(TransportType.All)]
         [InlineData((TransportType)0)]
         [InlineData(TransportType.LongPolling | TransportType.WebSockets)]
-        public async Task NegotiateReturnsAvailableTransports(TransportType transports)
+        public async Task NegotiateReturnsAvailableTransportsAfterFilteringByOptions(TransportType transports)
         {
             using (StartLog(out var loggerFactory, LogLevel.Debug))
             {
@@ -167,7 +167,8 @@ namespace Microsoft.AspNetCore.Sockets.Tests
                 var availableTransports = (TransportType)0;
                 foreach (var transport in negotiateResponse["availableTransports"])
                 {
-                    availableTransports |= (TransportType)Enum.Parse(typeof(TransportType), transport.Value<string>());
+                    var transportType = (TransportType)Enum.Parse(typeof(TransportType), transport.Value<string>("transport"));
+                    availableTransports |= transportType;
                 }
 
                 Assert.Equal(transports, availableTransports);
@@ -820,10 +821,10 @@ namespace Microsoft.AspNetCore.Sockets.Tests
         }
 
         [Theory]
-        [InlineData(TransportType.LongPolling, TransferMode.Binary | TransferMode.Text)]
+        [InlineData(TransportType.LongPolling, null)]
-        [InlineData(TransportType.ServerSentEvents, TransferMode.Text)]
+        [InlineData(TransportType.ServerSentEvents, TransferFormat.Text)]
-        [InlineData(TransportType.WebSockets, TransferMode.Binary | TransferMode.Text)]
+        [InlineData(TransportType.WebSockets, TransferFormat.Binary | TransferFormat.Text)]
-        public async Task TransportCapabilitiesSet(TransportType transportType, TransferMode expectedTransportCapabilities)
+        public async Task TransferModeSet(TransportType transportType, TransferFormat? expectedTransferFormats)
         {
             using (StartLog(out var loggerFactory, LogLevel.Debug))
             {
@@ -845,7 +846,11 @@ namespace Microsoft.AspNetCore.Sockets.Tests
                 options.WebSockets.CloseTimeout = TimeSpan.FromSeconds(0);
                 await dispatcher.ExecuteAsync(context, options, app);
 
-                Assert.Equal(expectedTransportCapabilities, connection.TransportCapabilities);
+                if (expectedTransferFormats != null)
+                {
+                    var transferFormatFeature = connection.Features.Get<ITransferFormatFeature>();
+                    Assert.Equal(expectedTransferFormats.Value, transferFormatFeature.SupportedFormats);
+                }
             }
         }
 

test/Microsoft.AspNetCore.Sockets.Tests/WebSocketsTests.cs

@@ -8,6 +8,8 @@ using System.Net.WebSockets;
 using System.Text;
 using System.Threading;
 using System.Threading.Tasks;
+using Microsoft.AspNetCore.Sockets.Features;
+using Microsoft.AspNetCore.Sockets.Internal;
 using Microsoft.AspNetCore.Sockets.Internal.Transports;
 using Microsoft.Extensions.Logging;
 using Microsoft.Extensions.Logging.Testing;
@@ -71,9 +73,9 @@ namespace Microsoft.AspNetCore.Sockets.Tests
         }
 
         [Theory]
-        [InlineData(TransferMode.Text, WebSocketMessageType.Text)]
+        [InlineData(TransferFormat.Text, WebSocketMessageType.Text)]
-        [InlineData(TransferMode.Binary, WebSocketMessageType.Binary)]
+        [InlineData(TransferFormat.Binary, WebSocketMessageType.Binary)]
-        public async Task WebSocketTransportSetsMessageTypeBasedOnTransferModeFeature(TransferMode transferMode, WebSocketMessageType expectedMessageType)
+        public async Task WebSocketTransportSetsMessageTypeBasedOnTransferFormatFeature(TransferFormat transferFormat, WebSocketMessageType expectedMessageType)
         {
             using (StartLog(out var loggerFactory, LogLevel.Debug))
             {
@@ -82,7 +84,8 @@ namespace Microsoft.AspNetCore.Sockets.Tests
 
                 using (var feature = new TestWebSocketConnectionFeature())
                 {
-                    var connectionContext = new DefaultConnectionContext(string.Empty, null, null) { TransferMode = transferMode };
+                    var connectionContext = new DefaultConnectionContext(string.Empty, null, null);
+                    connectionContext.ActiveFormat = transferFormat;
                     var ws = new WebSocketsTransport(new WebSocketOptions(), connection.Application, connectionContext, loggerFactory);
 
                     // Give the server socket to the transport and run it