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WebSocket Object Has been disposed on second Instance RRS feed

  • Question

  • Hi,

    I have a web app which needs to open an instance of socket server to listen to it's clients.

    I am using WebSockets to interact with server side socket instance.

    When I call javascript method of WebSocket from js file, handler invoked and it provide us the client instance to interact with.

    Problem:

    I open two tabs in browser, create two instances of WebSocket in other words. When I send message to second instance, it gives me "Cannot access because object has been disposed".

    Code:

    public class WebSocketsServer : IHttpHandler
        {
            public void ProcessRequest(HttpContext context)
            {
                if (context.IsWebSocketRequest)
                    context.AcceptWebSocketRequest(ProcessSocket);
            }
    
            private static bool _isServerStarted = false;
            WebSocket socket;
            public async Task ProcessSocket(AspNetWebSocketContext context)
            {
              socket = context.WebSocket;
              await AsynchronousSocketListener.StartListening(socket);
                _isServerStarted = true;
    
                return;
    
                AsynchronousSocketListener.StartListening(socket);
            }
    
            public bool IsReusable
            {
                get
                {
                    return false;
                }
            }
        }
    }
    AsynchronousSocketListener Class:

    using System; using System.Collections.Generic; using System.Linq; using System.Web; namespace WebApplication1 { using System; using System.Net; using System.Net.Sockets; using System.Net.WebSockets; using System.Text; using System.Threading; using System.Threading.Tasks; // State object for reading client data asynchronously public class StateObject { // Client socket. public Socket workSocket = null; // Size of receive buffer. public const int BufferSize = 1024; // Receive buffer. public byte[] buffer = new byte[BufferSize]; // Received data string. public StringBuilder sb = new StringBuilder(); } public class ListenerHandler { public Socket Socket; public WebSocket WebSocker; public StateObject state; } public class AsynchronousSocketListener { // Thread signal. public static ManualResetEvent allDone = new ManualResetEvent(false); static WebSocket webSocket; static Socket listener; public async static Task StartListening(WebSocket socket) { webSocket = socket; if (listener != null) return; // Data buffer for incoming data. byte[] bytes = new Byte[1024]; // Establish the local endpoint for the socket. // The DNS name of the computer // running the listener is "host.contoso.com". IPHostEntry ipHostInfo = Dns.Resolve(Dns.GetHostName()); IPAddress ipAddress = ipHostInfo.AddressList[0]; IPEndPoint localEndPoint = new IPEndPoint(ipAddress, 2596); // Create a TCP/IP socket. listener = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp); // Bind the socket to the local endpoint and listen for incoming connections. try { listener.Bind(localEndPoint); listener.Listen(100); while (true) { // Set the event to nonsignaled state. allDone.Reset(); // Start an asynchronous socket to listen for connections. Console.WriteLine("Waiting for a connection..."); listener.BeginAccept( new AsyncCallback(AcceptCallback), new ListenerHandler() { Socket = listener, WebSocker = socket }); // Wait until a connection is made before continuing. allDone.WaitOne(); } } catch (Exception e) { Console.WriteLine(e.ToString()); } Console.WriteLine("\nPress ENTER to continue..."); Console.Read(); } public static async Task SendMessage(WebSocket socket) { } public static void AcceptCallback(IAsyncResult ar) { // Signal the main thread to continue. allDone.Set(); var listenerHandler = (ListenerHandler)ar.AsyncState; // Get the socket that handles the client request. Socket listener = listenerHandler.Socket; Socket handler = listener.EndAccept(ar); // Create the state object. StateObject state = new StateObject(); state.workSocket = handler; handler.BeginReceive(state.buffer, 0, StateObject.BufferSize, 0, new AsyncCallback(ReadCallback), new ListenerHandler() { Socket = handler, WebSocker = listenerHandler.WebSocker, state = state }); } static int count = 0; public async static void ReadCallback(IAsyncResult ar) { count++; String content = String.Empty; // Retrieve the state object and the handler socket // from the asynchronous state object. var listenerHandler = (ListenerHandler)ar.AsyncState; StateObject state = listenerHandler.state; Socket handler = listenerHandler.Socket; // Read data from the client socket. int bytesRead = handler.EndReceive(ar); if (bytesRead > 0) { // There might be more data, so store the data received so far. state.sb.Append(Encoding.ASCII.GetString( state.buffer, 0, bytesRead)); // Check for end-of-file tag. If it is not there, read // more data. content = state.sb.ToString(); ArraySegment<byte> buffer = new ArraySegment<byte>(Encoding.UTF8.GetBytes("this is the message")); await listenerHandler.WebSocker.SendAsync(buffer, WebSocketMessageType.Text, true, CancellationToken.None); //AddClientMessage(content); //SendMessageToWebClients(); state.sb.Clear(); if (content.IndexOf("<EOF>") > -1) { state.buffer = new byte[StateObject.BufferSize]; state.sb.Clear(); handler.BeginReceive(state.buffer, 0, StateObject.BufferSize, 0, new AsyncCallback(ReadCallback), state); // All the data has been read from the // client. Display it on the console. Console.WriteLine("Read {0} bytes from socket. \n Data : {1}", content.Length, content); // Echo the data back to the client. Send(handler, content); } else { // Not all data received. Get more. handler.BeginReceive(state.buffer, 0, StateObject.BufferSize, 0, new AsyncCallback(ReadCallback), state); } } } private static void Send(Socket handler, String data) { // Convert the string data to byte data using ASCII encoding. byte[] byteData = Encoding.ASCII.GetBytes(data); // Begin sending the data to the remote device. handler.BeginSend(byteData, 0, byteData.Length, 0, new AsyncCallback(SendCallback), handler); } private static void SendCallback(IAsyncResult ar) { try { // Retrieve the socket from the state object. Socket handler = (Socket)ar.AsyncState; // Complete sending the data to the remote device. int bytesSent = handler.EndSend(ar); Console.WriteLine("Sent {0} bytes to client.", bytesSent); handler.Shutdown(SocketShutdown.Both); handler.Close(); } catch (Exception e) { Console.WriteLine(e.ToString()); } } public static int Main(String[] args) { //StartListening(); return 0; } private static bool isCompleted = true; public static List<WebClientInstance> _webClientInstances = new List<WebClientInstance>(); public async static void SendMessageToClient(WebClientInstance client) { try { if (client.Messages.Count > 0) { if (isCompleted) { isCompleted = false; var message = client.Messages[0]; client.Messages.RemoveAt(0); message = message.Substring(message.IndexOf("{")); message = message.Substring(0, message.IndexOf("}") + 1); ArraySegment<byte> buffer = new ArraySegment<byte>(Encoding.UTF8.GetBytes(message)); await webSocket.SendAsync(buffer, WebSocketMessageType.Text, true, CancellationToken.None); isCompleted = true; SendMessageToClient(client); } } else { } } catch(Exception ex) { } } private static List<WebSocket> _webClients = new List<WebSocket>(); public static void AddWebClient(WebSocket socket, string clientId) { var client = _webClientInstances.Where(c => c.ClientID == clientId).SingleOrDefault(); if (client != null) client.Socket.CloseAsync(WebSocketCloseStatus.Empty, "", CancellationToken.None); _webClientInstances.Clear(); _webClientInstances.Add(new WebClientInstance() { ClientID = clientId, Socket = socket }); } public static void AddClientMessage(string message) { foreach (var client in _webClientInstances) { client.Messages.Add(message); } } public static void SendMessageToWebClients() { foreach(var client in _webClientInstances) { SendMessageToClient(client); } } } public class WebClientInstance { public WebSocket Socket { get; set; } public string ClientID { get; set; } private List<string> _messages = new List<string>(); public List<string> Messages { get { return _messages; } set { _messages = value; } } } }

    Please Help!

    Sunday, March 27, 2016 9:12 AM

All replies

  • Hello,

     Are the WebSocket object created inside or outside of the handler? If you create them inside then when

    the handler exits, that is for non-static methods, all objects created upon entry are Dispose on exit.  Is

    this possibly what is occuring? If not, can you single step thru to see where the Debugger is calling the

    Dispose?

     Thanks :)

    Sunday, March 27, 2016 9:33 AM