// Thread signal.
public static ManualResetEvent clientConnected =
    new ManualResetEvent(false);

// Accept one client connection asynchronously.
public static void DoBeginAcceptSocket(TcpListener listener)
{
    // Set the event to nonsignaled state.
    clientConnected.Reset();

    // Start to listen for connections from a client.
    Console.WriteLine("Waiting for a connection...");

    // Accept the connection.
    // BeginAcceptSocket() creates the accepted socket.
    listener.BeginAcceptSocket(
        new AsyncCallback(DoAcceptSocketCallback), listener);
    // Wait until a connection is made and processed before
    // continuing.
    clientConnected.WaitOne();
}

// Process the client connection.
public static void DoAcceptSocketCallback(IAsyncResult ar)
{
    // Get the listener that handles the client request.
    TcpListener listener = (TcpListener) ar.AsyncState;

    // End the operation and display the received data on the
    //console.
    Socket clientSocket = listener.EndAcceptSocket(ar);

    // Process the connection here. (Add the client to a
    // server table, read data, etc.)
    Console.WriteLine("Client connected completed");

    // Signal the calling thread to continue.
    clientConnected.Set();
}