Allow starting connection only once

client-ts/Microsoft.AspNetCore.SignalR.Client.TS.Tests/Connection.spec.ts

@@ -27,4 +27,70 @@ describe("Connection", () => {
             done();
         }
     });
+
+    it("cannot start a running connection", async (done) => {
+        let options: ISignalROptions = {
+            httpClient: <IHttpClient>{
+                get(url: string): Promise<string> {
+                    if (url.indexOf("/negotiate") >= 0) {
+                        connection.start()
+                            .then(() => {
+                                fail();
+                                done();
+                            })
+                            .catch((error: Error) => {
+                                expect(error.message).toBe("Cannot start a connection that is not in the 'Initial' state.");
+                                done();
+                            });
+
+                        return Promise.reject("error");
+                    }
+                    return Promise.resolve("");
+                }
+            }
+        } as ISignalROptions;
+
+        let connection = new Connection("http://tempuri.org", undefined, options);
+
+        try {
+            await connection.start();
+        }
+        catch (e) {
+            // This exception is thrown after the actual verification is completed.
+            // The connection is not setup to be running so just ignore the error.
+        }
+    });
+
+    it("cannot start a stopped connection", async (done) => {
+        let options: ISignalROptions = {
+            httpClient: <IHttpClient>{
+                get(url: string): Promise<string> {
+                    if (url.indexOf("/negotiate") >= 0) {
+                        return Promise.reject("error");
+                    }
+                    return Promise.resolve("");
+                }
+            }
+        } as ISignalROptions;
+
+        let connection = new Connection("http://tempuri.org", undefined, options);
+
+        try {
+            // start will fail and transition the connection to the Disconnected state
+            await connection.start();
+        }
+        catch (e) {
+            // The connection is not setup to be running so just ignore the error.
+        }
+
+        try {
+            await connection.start();
+            fail();
+            done();
+        }
+        catch (e) {
+            expect(e.message).toBe("Cannot start a connection that is not in the 'Initial' state.");
+            done();
+        }
+    });
 });

client-ts/Microsoft.AspNetCore.SignalR.Client.TS/Connection.ts

@@ -5,9 +5,10 @@ import { IHttpClient, HttpClient } from "./HttpClient"
 import { ISignalROptions } from "./ISignalROptions"
 
 enum ConnectionState {
-    Disconnected,
+    Initial,
     Connecting,
-    Connected
+    Connected,
+    Disconnected
 }
 
 export class Connection implements IConnection {
@@ -22,14 +23,16 @@ export class Connection implements IConnection {
         this.url = url;
         this.queryString = queryString;
         this.httpClient = options.httpClient || new HttpClient();
-        this.connectionState = ConnectionState.Disconnected;
+        this.connectionState = ConnectionState.Initial;
     }
 
     async start(transportName: string = "webSockets"): Promise<void> {
-        if (this.connectionState != ConnectionState.Disconnected) {
-            throw new Error("Cannot start a connection that is not in the 'Disconnected' state");
+        if (this.connectionState != ConnectionState.Initial) {
+            throw new Error("Cannot start a connection that is not in the 'Initial' state.");
         }
 
+        this.connectionState = ConnectionState.Connecting;
+
         this.transport = this.createTransport(transportName);
         this.transport.onDataReceived = this.onDataReceived;
         this.transport.onClosed = e => this.stopConnection(e);