C#•2y 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

/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");
  }
}

[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");
  }
}

TeBeCo•4/4/24, 9:21 PM

why do you not use that tcs ?

TeBeCo•4/4/24, 9:23 PM

what's that infinite loop also ?

TeBeCo•4/4/24, 9:23 PM

i would move most of that code elsewhere

TeBeCo•4/4/24, 9:24 PM

you already created a service but putted code here unsure why

TTeBeCo what's that infinite loop also ?

AlexOP•4/4/24, 9:54 PM

I made infinite loop temporary because otherwise the connection with client closes immediately. This is my

WebSocketManagerService

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

Pastebin

public class WebSocketManagerService : IWebSocketManagerService{ ...

Pastebin.com is the number one paste tool since 2002. Pastebin is a website where you can store text online for a set period of time.

TeBeCo•4/4/24, 9:54 PM

you created a TCS

TeBeCo•4/4/24, 9:55 PM

which you could use to await instead of the loop

TeBeCo•4/4/24, 9:55 PM

that's the goal of TCS

TeBeCo•4/4/24, 10:07 PM

until you explicitly Complete it

TTeBeCo that's the goal of TCS

AlexOP•4/4/24, 10:07 PM

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

TeBeCo•4/4/24, 10:10 PM

you don't need that loop

TeBeCo•4/4/24, 10:10 PM

it will throw when you'll deal with the socket

TeBeCo•4/4/24, 10:11 PM

like sending/reading

TeBeCo•4/4/24, 10:13 PM

you're supposed to either observe a Close Message

TeBeCo•4/4/24, 10:13 PM

or an exception when it's gone / aborted

TeBeCo•4/4/24, 10:14 PM

https://learn.microsoft.com/en-us/aspnet/core/fundamentals/websockets?view=aspnetcore-8.0

WebSockets support in ASP.NET Core

Learn how to get started with WebSockets in ASP.NET Core.

TeBeCo•4/4/24, 10:14 PM

TeBeCo•4/4/24, 10:15 PM

don't ask where is

BackgroundSocketProcessor

BackgroundSocketProcessor

TeBeCo•4/4/24, 10:15 PM

it's code that is not shared anywhere, as MSFT don't want to be responsible for what's should be X or Y way of handling it

TeBeCo•4/4/24, 10:16 PM

most of the time you're adding the client to a thread safe collection

TeBeCo•4/4/24, 10:16 PM

and also have a Task.Run started for each to read data

TeBeCo•4/4/24, 10:16 PM

and maybe another one to send

TTeBeCo don't ask where is `BackgroundSocketProcessor` 😄

AlexOP•4/4/24, 10:16 PM

yes, I have this part

AAlex yes, I have this part

TeBeCo•4/4/24, 10:17 PM

then you shouldn't have have the code for the send above of the while loop

TeBeCo•4/4/24, 10:18 PM

TeBeCo•4/4/24, 10:18 PM

most of it moves into the background processor

TeBeCo•4/4/24, 10:19 PM

because your code was doing send

TeBeCo•4/4/24, 10:19 PM

which is supposed to be after you've joined

TeBeCo•4/4/24, 10:19 PM

which if what your

.Add

.Add

TeBeCo•4/4/24, 10:19 PM

and thing disconnect can only be pluged on the other hand

TeBeCo•4/4/24, 10:19 PM

the removal also should probably be there

TTeBeCo then you shouldn't have have the code for the send above of the while loop

AlexOP•4/4/24, 10:19 PM

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)

TeBeCo•4/4/24, 10:20 PM

and why are you not using SignalR for that if you say your clietn is REACT ?

TeBeCo•4/4/24, 10:20 PM

sounds exactly what SignalR does for you

AlexOP•4/4/24, 10:22 PM

I thought it will be easier to use web sockets because SignalR has hubs and etc. Is it better to use SignalR?

AlexOP•4/4/24, 10:26 PM

I have never used web sockets, signalR or sse, so I decided to start with something that doesn't look complex

TeBeCo•4/4/24, 10:27 PM

signalr handle http connection for you

TeBeCo•4/4/24, 10:27 PM

which is WSS or SSE automatically

TeBeCo•4/4/24, 10:27 PM

and the hub is literally your WSS endpoint

TeBeCo•4/4/24, 10:27 PM

it's the same

TeBeCo•4/4/24, 10:27 PM

it avoid you to code something like a

message { topic = join, value = abc}

message { topic = join, value = abc}

TeBeCo•4/4/24, 10:28 PM

it's a

JoinMessage ( abc )

JoinMessage ( abc )

with a method

Join

Join

on the hub

TeBeCo•4/4/24, 10:28 PM

it's close to RPC

TTeBeCo it's close to RPC

AlexOP•4/4/24, 10:39 PM

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);
      }

TeBeCo•4/4/24, 10:40 PM

i'm of computer for today

TTeBeCo i'm of computer for today

AlexOP•4/4/24, 10:42 PM

yes it's late, thank you for help, I'll try to fix it tomorrow

TTeBeCo and why are you not using SignalR for that if you say your clietn is REACT ?

AlexOP•4/6/24, 10:29 AM

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?

Web sockets management

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