silverlight socket: implement two-way communications?

Question

I basically try to reproduce the Socket example from here: http://www.silverlightshow.net/items/Sockets-and-their-implementation-in-SL2-Beta-1-including-a-chat-like-example.aspx. I have been able to get the message send from Client To Server using the following code. But how can the server response to client?

Client Code:

String safeHost = Application.Current.Host.Source.DnsSafeHost;
            int port = 4509;
            socketClient = new SocketClient(
                                        safeHost,
                                        port);

            socketClient.Connected += new EventHandler(socketClient_Connected);
            socketClient.Connect();
        }
        Send();
    }

    void socketClient_Connected(object sender, EventArgs e)
    {
        //Say("Connected");
        //ConnectButton.Content = "Disconnect";
    }

    private void Send()
    {
        if (socketClient.IsConnected)
        {
            socketClient.SendReceive("Test Message");
            //Say("you said: " + Keyboard.Text);

        }
    }

Server Code:

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 AsynchronousSocketListener { // Thread signal. public static ManualResetEvent allDone = new ManualResetEvent( false );

public AsynchronousSocketListener()
{
}

public static void StartListening()
{
    // 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.GetHostEntry( Dns.GetHostName() );
    IPAddress ipAddress =   // localhost
                            IPAddress.Parse( "127.0.0.1" );
    IPEndPoint localEndPoint =  //4509 is one of the available
        //ports in Silverlight 2 Beta 1
                                new IPEndPoint( ipAddress, 4509 );

    // Create a TCP/IP socket.
    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 ),
                listener );

            // 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 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.
    StateObject state = new StateObject();
    state.workSocket = handler;
    handler.BeginReceive( state.buffer, 0, StateObject.BufferSize, 0,
        new AsyncCallback( ReadCallback ), state );
}

public static void ReadCallback( IAsyncResult ar )
{
    String content = String.Empty;

    // Retrieve the state object and the handler socket
    // from the asynchronous state object.
    StateObject state = ( StateObject )ar.AsyncState;
    Socket handler = state.workSocket;

    // Read data from the client socket. 
    //byte[] buffer = new byte[1024];
    int bytesRead = handler.EndReceive( ar );

    if( bytesRead > 0 )
    {
        // There  might be more data, so store the data received so far.
        state.sb = new StringBuilder();
        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 = //( String )buffer.ToString();
                     state.sb.ToString();

        if( content.IndexOf( "<EOF>" ) > -1 )
        {
            //All the data has been read from the 
            //client. Display it on the console.
            Console.WriteLine( "Client quit: {1}",
                content.Length, content );
            //Echo the data back to the client.
            //Send( handler, content );
            handler.Shutdown( SocketShutdown.Both ); handler.Close();
        }
        else
        {
            Console.WriteLine( "Client said: {1}",
content.Length, content );
            // 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 )
{
    PolicyServer ps = new PolicyServer();
    ps.Start();

    StartListening();
    //then when shutting down 
    ps.Stop();
    return 0;

}