CODEWITHSUNDEEP
c#asp.netwebsockethandshake
Josh
Josh

Reputation: 165

How to handle the close handshake c#

i developed a guessing game in c# using websockets and https calls. Each time the user is creating an instance of the console application to play, it connects with the server. (await webSocket.ConnectAsync(new Uri("ws://localhost:xxx"), CancellationToken.None);).

I have a websocketmiddlewear class to accept the websocket reqeust and a manager class where i handle the websockets requests. Everything works fine except when the user exit the console game. For example when i press "x" from the console (cmd) i get the following error

The remote party closed the WebSocket connection without completing the close handshake.

on the following line

WebSocketReceiveResult result = await socket.ReceiveAsync(new ArraySegment<byte>(buffer), CancellationToken.None);

Why the code is not handling the error and how i can fix it?

ConnectionManagerService.cs

 public async Task Receive(WebSocket socket)
        {
            var buffer = new byte[1024 * 4];

            while (socket.State == WebSocketState.Open)
            {
                WebSocketReceiveResult result = await socket.ReceiveAsync(new ArraySegment<byte>(buffer), CancellationToken.None);


               if (result.MessageType == WebSocketMessageType.Text)
                {
                    Console.WriteLine($"Receive->Text");      
                    return;   
                }
                else if (result.MessageType == WebSocketMessageType.Close)
                {
                    string id = _sockets.FirstOrDefault(s => s.Value == socket).Key;
                    //Console.WriteLine($"Receive->Close on: " + id);

                    _sockets.TryRemove(id, out socket);
                    Console.WriteLine("Managed Connections: " + _sockets.Count.ToString());

                    await socket.CloseOutputAsync(result.CloseStatus.Value, result.CloseStatusDescription, CancellationToken.None);
                    return;
                }
            }
        }
 

WebsocketMiddleware.cs

        }
        public async Task Invoke(HttpContext context)
        {
            var isSocketRequest = context.WebSockets.IsWebSocketRequest;
            if (isSocketRequest)
            {
                WebSocket socket = await context.WebSockets.AcceptWebSocketAsync();   
                _manager.AddSocket(socket);    
                await _manager.Receive(socket);

            }
            else
            {
                await _next(context);
            }
        }

Upvotes: 1

Views: 2303

Answers (1)

Bercovici Adrian
Bercovici Adrian

Reputation: 9360

It happens because you are treating only the graceful connection disconnect.The client might just disconnect and you will get big ol SocketIO Exception in the middle of a read/write operation.

Consider wrapping your Socket operation(s) in a try-catch and deal with them as you please.

public async Task Receive(WebSocket socket)
        {
            var buffer = new byte[1024 * 4];
            try{
                while (true) 
                {
                    WebSocketReceiveResult result = await socket.ReceiveAsync(new ArraySegment<byte>(buffer), CancellationToken.None);
                    if (result.MessageType == WebSocketMessageType.Text)
                    {
                        Console.WriteLine($"Receive->Text");      
                        return;   
                    }
                    else if (result.MessageType == WebSocketMessageType.Close)
                    {
                    string id = _sockets.FirstOrDefault(s => s.Value == socket).Key;
                    //Console.WriteLine($"Receive->Close on: " + id);

                    _sockets.TryRemove(id, out socket);
                    Console.WriteLine("Managed Connections: " + _sockets.Count.ToString());

                    await socket.CloseOutputAsync(result.CloseStatus.Value, result.CloseStatusDescription, CancellationToken.None);
                    return;
                    }
                } 
            } catch(Exception ex){   //not so graceful disconnect
                 _sockets.TryRemove(id, out socket);
                    //deal with closed connection 
                    //maybe reconnect ?
            }
        }

Upvotes: 2

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