public void AcceptCallback(IAsyncResult ar)
{
// Signal the main thread to continue.
// allDone.Set();
// Get the socket that handles the client request.
Socket listener = (Socket)ar.AsyncState;
Socket handler = listener.EndAccept(ar);
// Create the state object.
SocketState state = new SocketState();
state.workSocket = handler;
BeginAccept(listener);
state.BeginReceive();
}