SignalR：协商有效，但消息未发送(.NETAngular)

我试图获得一个非常基本的SignalR示例，它基于Microsoft's tutorial和由Visual Studio创建的WeatherForecast.NET/ANGLE SPA作为基础，因为这是我以后想要使用SignalR的同一类型的项目.The entire source code is at GitHub.

It looks as if the handshake/negotiation works and a websocket connection is established - but no messages are flowing there. This is what the Chrome Developer Tools show:

我感觉我忽略了一些小问题，但我正在努力想知道它可能是什么.

我从调整Program.cs文件开始，这是相关代码:

builder.Services.AddSignalR(options =>
{
    options.EnableDetailedErrors = true;
});

var app = builder.Build();

...

app.UseCors();
  
//app.MapHub<ProgressHub>("/progressHub");
app.UseEndpoints(endpoints =>
{
    endpoints.MapHub<ProgressHub>("/progresshub"); // Map the hub URL here
});

app.Run();

请注意，MS建议使用app.MapHub<ProgressHub>("/progressHub");，但SOM资源建议使用app.UseEndpoints.这似乎没有什么不同.此外，我try 使用app.UseWebSockets();，但这也没有改变任何事情.此外，我还确保启用了CORS.

这是我添加的控制器方法，它应该在SignalR通道上发送消息:

[HttpPost("startProcess")]
public async Task<IActionResult> StartProcess()
{
    // Some logic to start the long-running process
    for (int i = 0; i < 10; i++)
    {
        await Task.Delay(1000);

        // Report progress to the client
        await _hubContext.Clients.All.SendAsync("ReceiveProgressUpdate", $"Step {i + 1} completed.");
    }

    return Ok("[]");
}

单步执行代码时，不会引发任何异常，代码运行时没有任何问题.在ANGLE客户端，我安装了SignalR包并创建了一个服务:

export class SignalRService {
  private hubConnection: HubConnection;
  private progressSubject: Subject<string> = new Subject<string>();

  constructor() {
    this.hubConnection = new HubConnectionBuilder()
      .withUrl('https://localhost:44429/progresshub')
      .build();

    this.hubConnection.on('ReceiveProgressUpdate', (progressMessage: string) => {
      this.progressSubject.next(progressMessage);
    });

    this.hubConnection.start().catch(err => console.error(err));
  }

  getProgressUpdates() {
    return this.progressSubject.asObservable();
  }
}

现在，我在我的SignalR组件中使用了该服务，但ProgressUpdates数组仍然为空:

export class SignalRComponent implements OnInit {
  progressUpdates: string[] = [];
  _httpClient: HttpClient;

  constructor(private httpClient: HttpClient, private signalRService: SignalRService) {
    this._httpClient = httpClient;
  }

  ngOnInit() {
    this.signalRService.getProgressUpdates().subscribe((progressMessage: string) => {
      this.progressUpdates.push(progressMessage);
    });
  }

  startProcess() {
    this.httpClient.post('https://localhost:44429/weatherforecast/startProcess', {}).subscribe();
  }
}

Also, I have turned on the WebSocket Protocol in Windows as this was suggested on SO as well: