public class Example
  {
    static ManualResetEvent clientDone = new ManualResetEvent(false);

    public static void Demo(System.Windows.Controls.TextBlock outputBlock)
    {

        SocketAsyncEventArgs socketEventArg = new SocketAsyncEventArgs();
            DnsEndPoint hostEntry = new DnsEndPoint("http://www.contoso.com", 80);

        // Create a socket and connect to the server
        Socket sock = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);

        socketEventArg.Completed += new EventHandler<SocketAsyncEventArgs>(SocketEventArg_Completed);

        socketEventArg.RemoteEndPoint = hostEntry;
        socketEventArg.UserToken = sock;
        sock.ConnectAsync(socketEventArg);
        clientDone.WaitOne();
    }

    // A single callback is used for all socket operations. 
    // This method forwards execution on to the correct handler 
    // based on the type of completed operation
    static void SocketEventArg_Completed(object sender, SocketAsyncEventArgs e)
    {
        switch (e.LastOperation)
        {
            case SocketAsyncOperation.Connect:
                ProcessConnect(e);
                break;
            case SocketAsyncOperation.Receive:
                ProcessReceive(e);
                break;
            case SocketAsyncOperation.Send:
                ProcessSend(e);
                break;
            default:
                throw new Exception("Invalid operation completed");
        }
    }

    // Called when a ConnectAsync operation completes
    private static void ProcessConnect(SocketAsyncEventArgs e)
    {
        if (e.SocketError == SocketError.Success)
        {
            // Successfully connected to the server

            // Send 'Hello World' to the server
            byte[] buffer = Encoding.UTF8.GetBytes("Hello World");
            e.SetBuffer(buffer, 0, buffer.Length);
            Socket sock = e.UserToken as Socket;
            bool willRaiseEvent = sock.SendAsync(e);
            if (!willRaiseEvent)
            {
                ProcessSend(e);
            }
        }
        else
        {
            throw new SocketException((int)e.SocketError);
        }
    }

        // Called when a ReceiveAsync operation completes
        // </summary>
    private static void ProcessReceive(SocketAsyncEventArgs e)
    {
        if (e.SocketError == SocketError.Success)
        {
            // Received data from server

        // Data has now been sent and received from the server. 
        // Disconnect from the server
            Socket sock = e.UserToken as Socket;
            sock.Shutdown(SocketShutdown.Send);
            sock.Close();
            clientDone.Set();
        }
        else
        {
            throw new SocketException((int)e.SocketError);
        }
    }


    // Called when a SendAsync operation completes
    private static void ProcessSend(SocketAsyncEventArgs e)
    {
        if (e.SocketError == SocketError.Success)
        {
            // Sent "Hello World" to the server successfully

            //Read data sent from the server
            Socket sock = e.UserToken as Socket;
            bool willRaiseEvent = sock.ReceiveAsync(e);
            if (!willRaiseEvent)
            {
                ProcessReceive(e);
            }
        }
        else
        {
            throw new SocketException((int)e.SocketError);
        }
    }
  }