Unable to close socket after BeginAccept method

Question

I have a program in C # in which I create a socket by binding it, start listening, and then with beginaccept! but then when I try to close the \ shutdown socket, I get exceptions from the beginaccept AsyncCallback method!

private void start_listening() { main_socket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp); IPEndPoint iplocal = new IPEndPoint(IPAddress.Any, 11150); main_socket.Bind(iplocal); main_socket.Listen(5); main_socket.BeginAccept(new AsyncCallback(OnClientConnect), null); } private void Disconnect_Click(object sender, EventArgs e) { main_socket.Shutdown(SocketShutdown.Both); main_socket.Close(); } public void OnClientConnect(IAsyncResult asyn) { try { clients[connected_clients] = new Client("CHANGEME", "127.0.0.1", this); clients[connected_clients].Socket = main_socket.EndAccept(asyn); clients[connected_clients].WaitForData(); main_socket.BeginAccept(OnClientConnect, null); } catch (SocketException se) { MessageBox.Show(se.Message); } } 

many thanks!

Answer 1

When main_socket is closed, OnClientConnect () is called, but main_socket.EndAccept () should throw an ObjectDisposedException. Perhaps you want to catch this exception and treat it like the message "Close listener socket".

Another problem with your code is that main_socket is not actually related to anything. A call to main_socket.Shutdown () on Disconnect_Click () can also be fired, but this time it should be a SocketException saying that the socket is not connected. I would remove this call to main_socket.Shutdown ().

Answer 2

An old topic, but one solution: keep a local variable to keep track of when you "close / close" the socket. I am using _isShutdown .

When you start listening to a socket, set _isShutDown = False;
Before closing the outlet, set _isShutdown = True;

In the EndAccept(iar) function, call only

  socket.EndAccept() when _isShutdown is false <pre><code> 

 if (_isShutdown == false) { someWorkSocket = listenSocket.EndAccept(iaSyncResult); //... } else { //socket is closed, and we shouldn't use it. Should erase this else clause.. } 

Answer 3

"To cancel the pending call to the BeginAccept method, close Socket. When the Close method is called during an asynchronous operation, the callback provided to the BeginAccept method is called . A subsequent call to the EndAccept method will raise an ObjectDisposedException to indicate that the operation has been canceled."

Socket.BeginAccept Method (AsyncCallback, Object)

the correct way could be:
1) create a client socket on the server, connect to the listening socket, after successful completion EndAccept close it
2) the method suggested by MSDN is to simply handle this exception as