Detect ASP.NET SignalR server connection attempt (#2820)

clients/ts/signalr/src/HttpConnection.ts

@@ -146,6 +146,10 @@ export class HttpConnection implements IConnection {
                         return;
                     }
 
+                    if ((negotiateResponse as any).ProtocolVersion) {
+                        throw Error("Detected a connection attempt to an ASP.NET SignalR Server. This client only supports connecting to an ASP.NET Core SignalR Server. See https://aka.ms/signalr-core-differences for details.");
+                    }
+
                     if (negotiateResponse.url) {
                         url = negotiateResponse.url;
                     }

clients/ts/signalr/tests/HttpConnection.test.ts

@@ -794,5 +794,38 @@ describe("HttpConnection", () => {
                 expect(() => connection.start(42)).toThrowError("Unknown transferFormat value: 42.");
             });
         });
+
+        it("throws if trying to connect to an ASP.NET SignalR Server", async () => {
+            await VerifyLogger.run(async (logger) => {
+                const options: IHttpConnectionOptions = {
+                    ...commonOptions,
+                    httpClient: new TestHttpClient()
+                        .on("POST", () => "{\"Url\":\"/signalr\"," +
+                            "\"ConnectionToken\":\"X97dw3uxW4NPPggQsYVcNcyQcuz4w2\"," +
+                            "\"ConnectionId\":\"05265228-1e2c-46c5-82a1-6a5bcc3f0143\"," +
+                            "\"KeepAliveTimeout\":10.0," +
+                            "\"DisconnectTimeout\":5.0," +
+                            "\"TryWebSockets\":true," +
+                            "\"ProtocolVersion\":\"1.5\"," +
+                            "\"TransportConnectTimeout\":30.0," +
+                            "\"LongPollDelay\":0.0}")
+                        .on("GET", () => ""),
+                    logger,
+                } as IHttpConnectionOptions;
+
+                const connection = new HttpConnection("http://tempuri.org", options);
+                let receivedError = false;
+                try {
+                    await connection.start(TransferFormat.Text);
+                } catch (error) {
+                    expect(error).toEqual(new Error("Detected a connection attempt to an ASP.NET SignalR Server. This client only supports connecting to an ASP.NET Core SignalR Server. See https://aka.ms/signalr-core-differences for details."));
+                    receivedError = true;
+                } finally {
+                    await connection.stop();
+                }
+                expect(receivedError).toBe(true);
+            },
+            "Failed to start the connection: Error: Detected a connection attempt to an ASP.NET SignalR Server. This client only supports connecting to an ASP.NET Core SignalR Server. See https://aka.ms/signalr-core-differences for details.");
+        });
     });
 });

src/Microsoft.AspNetCore.Http.Connections.Common/NegotiateProtocol.cs

@@ -18,6 +18,8 @@ namespace Microsoft.AspNetCore.Http.Connections
         private const string AvailableTransportsPropertyName = "availableTransports";
         private const string TransportPropertyName = "transport";
         private const string TransferFormatsPropertyName = "transferFormats";
+        // Used to detect ASP.NET SignalR Server connection attempt
+        private const string ProtocolVersionPropertyName = "ProtocolVersion";
 
         public static void WriteResponse(NegotiationResponse response, IBufferWriter<byte> output)
         {
@@ -134,6 +136,8 @@ namespace Microsoft.AspNetCore.Http.Connections
                                             }
                                         }
                                         break;
+                                    case ProtocolVersionPropertyName:
+                                        throw new InvalidOperationException("Detected a connection attempt to an ASP.NET SignalR Server. This client only supports connecting to an ASP.NET Core SignalR Server. See https://aka.ms/signalr-core-differences for details.");
                                     default:
                                         reader.Skip();
                                         break;

test/Microsoft.AspNetCore.Http.Connections.Tests/NegotiateProtocolTests.cs

@@ -55,6 +55,27 @@ namespace Microsoft.AspNetCore.Http.Connections.Tests
             Assert.Equal(expectedMessage, exception.InnerException.Message);
         }
 
+        [Fact]
+        public void ParsingAspNetSignalRResponseThrowsError()
+        {
+            var payload = "{\"Url\":\"/signalr\"," +
+                "\"ConnectionToken\":\"X97dw3uxW4NPPggQsYVcNcyQcuz4w2\"," +
+                "\"ConnectionId\":\"05265228-1e2c-46c5-82a1-6a5bcc3f0143\"," +
+                "\"KeepAliveTimeout\":10.0," +
+                "\"DisconnectTimeout\":5.0," +
+                "\"TryWebSockets\":true," +
+                "\"ProtocolVersion\":\"1.5\"," +
+                "\"TransportConnectTimeout\":30.0," +
+                "\"LongPollDelay\":0.0}";
+
+            var responseData = Encoding.UTF8.GetBytes(payload);
+            var ms = new MemoryStream(responseData);
+
+            var exception = Assert.Throws<InvalidDataException>(() => NegotiateProtocol.ParseResponse(ms));
+
+            Assert.Equal("Detected a connection attempt to an ASP.NET SignalR Server. This client only supports connecting to an ASP.NET Core SignalR Server. See https://aka.ms/signalr-core-differences for details.", exception.InnerException.Message);
+        }
+
         [Fact]
         public void WriteNegotiateResponseWithNullAvailableTransports()
         {

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

@@ -83,7 +83,7 @@ namespace Microsoft.AspNetCore.SignalR.Client.Tests
             }
 
             [Fact]
-            public async Task NegotiateReturnedConenctionIdIsSetOnConnection()
+            public async Task NegotiateReturnedConnectionIdIsSetOnConnection()
             {
                 string connectionId = null;