C#•6mo ago

Web sockets management

Hello! I don't understand how to hold a connection with client and how to detect when it was closed by client and remove it from list. I have route where users can subscribe to notification /notifications/sub. There I accept web socket and add it to dictionary, id is assigned to each web socket. Then I do the "while" loop because otherwise the connection closes immediately. Also I have a problem that if I close browsers is not removed from dictionary that I use to send messages? Is there a way to solve these problems?

[HttpGet("sub")]
public async Task Subscribe() {
  if (HttpContext.WebSockets.IsWebSocketRequest) {
    using WebSocket ws = await HttpContext.WebSockets.AcceptWebSocketAsync();

    string key = _socketManagerService.AddSocket(ws);

    await _socketManagerService.SendAsync(
        key, new WebSocketMessage{
                 MessageType = MessageType.ConnectionEvent,
                 Data = new WebSocketMessageData{
                     Topic = "Connection",
                     Payload = $"Connection established {DateTime.UtcNow}"}});

    _logger.LogInformation($"New connection: {key} - {DateTime.UtcNow}");

    while (ws.State == WebSocketState.Open) {
    }
    await _socketManagerService.RemoveSocketAsync(key);
    _logger.LogInformation($"Connection closed {key} - {DateTime.UtcNow}");
    // var socketFinishedTcs = new TaskCompletionSource<object>();
    // await socketFinishedTcs.Task;
  } else {
    throw new BadRequestException("Only web socket connections");
  }
}

[HttpGet("sub")]
public async Task Subscribe() {
  if (HttpContext.WebSockets.IsWebSocketRequest) {
    using WebSocket ws = await HttpContext.WebSockets.AcceptWebSocketAsync();

    string key = _socketManagerService.AddSocket(ws);

    await _socketManagerService.SendAsync(
        key, new WebSocketMessage{
                 MessageType = MessageType.ConnectionEvent,
                 Data = new WebSocketMessageData{
                     Topic = "Connection",
                     Payload = $"Connection established {DateTime.UtcNow}"}});

    _logger.LogInformation($"New connection: {key} - {DateTime.UtcNow}");

    while (ws.State == WebSocketState.Open) {
    }
    await _socketManagerService.RemoveSocketAsync(key);
    _logger.LogInformation($"Connection closed {key} - {DateTime.UtcNow}");
    // var socketFinishedTcs = new TaskCompletionSource<object>();
    // await socketFinishedTcs.Task;
  } else {
    throw new BadRequestException("Only web socket connections");
  }
}

14 Replies

Unknown User•6mo ago

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Alex•6mo ago

I made infinite loop temporary because otherwise the connection with client closes immediately. This is my WebSocketManagerService. I store tasks in dictionary, but I don't know what to do next and how can I await for them. I also tried to await for the Task inside Subscribe method, you can see the commented part, but I couldn't connect from client WebSocketManagerService: https://pastebin.com/98d5UzET

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public class WebSocketManagerService : IWebSocketManagerService{ ...

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Unknown User•6mo ago

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Alex•6mo ago

ok I think now it shows that client is connected with tcs, but how can I detect when user is disconnected without loop?

Unknown User•6mo ago

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Alex•6mo ago

yes, I have this part

Unknown User•6mo ago

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Alex•6mo ago

yes, maybe I had problem with React that it couldn't connect to ws after a replaced loop with await tsc. I'm right now trying to see the ws ids I have in my dictionary to see if they actually removed after client disconnects (or if it even detects it)

Unknown User•6mo ago

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Alex•6mo ago

I thought it will be easier to use web sockets because SignalR has hubs and etc. Is it better to use SignalR? I have never used web sockets, signalR or sse, so I decided to start with something that doesn't look complex

Unknown User•6mo ago

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Alex•6mo ago

I added code to remove web socket from dictionary if the state is not open, but I still can see them in my dictionary? I checked that ws should close automatically if there isn't connection to client. or does it throw an exception and should I put code it try catch?

      public async Task SendAsync(string key, WebSocketMessage message)
      {
          WebSocket? ws = GetByKey(key);

          if (ws == null) return;

          if (ws.State != WebSocketState.Open)
          {
              _sockets.Remove(key, out _);
              return;
          }

          await SendMessageAsync(ws, message);
      }

      public async Task SendAsync(string key, WebSocketMessage message)
      {
          WebSocket? ws = GetByKey(key);

          if (ws == null) return;

          if (ws.State != WebSocketState.Open)
          {
              _sockets.Remove(key, out _);
              return;
          }

          await SendMessageAsync(ws, message);
      }

Unknown User•6mo ago

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Alex•6mo ago

yes it's late, thank you for help, I'll try to fix it tomorrow 😀 I've tried signalR and decided to use it for my project, it looks easy to manage than websockets. Also if it's possible can I ask you a question about react?

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Web sockets management