this.tcpListener = new TcpListener(IPAddress.Loopback, 3000); // Change to IPAddress.Any for internet wide Communication 
            this.listenThread = new Thread(new ThreadStart(ListenForClients)); 
            this.listenThread.Start();

 private void ListenForClients() 

        { 
            this.tcpListener.Start(); 
 
            while (true) // Never ends until the Server is closed. 
            { 
                //blocks until a client has connected to the server 
                TcpClient client = this.tcpListener.AcceptTcpClient(); 
 
                //create a thread to handle communication  
                //with connected client 
                connectedClients++; // Increment the number of clients that have communicated with us. 
                lblNumberOfConnections.Text = connectedClients.ToString(); 
 
                Thread clientThread = new Thread(new ParameterizedThreadStart(HandleClientComm)); 
                clientThread.Start(client); 
            } 
        }

private void HandleClientComm(object client) 

        { 
            TcpClient tcpClient = (TcpClient)client; 
            NetworkStream clientStream = tcpClient.GetStream(); 
 
            byte[] message = new byte[4096]; 
            int bytesRead; 
 
            while (true) 
            { 
                bytesRead = 0; 
 
                try 
                { 
                    //blocks until a client sends a message 
                    bytesRead = clientStream.Read(message, 0, 4096); 
                } 
                catch 
                { 
                    //a socket error has occured 
                    break; 
                } 
 
                if (bytesRead == 0) 
                { 
                    //the client has disconnected from the server 
                    connectedClients--; 
                    lblNumberOfConnections.Text = connectedClients.ToString(); 
                    break; 
                } 
 
                //message has successfully been received 
                ASCIIEncoding encoder = new ASCIIEncoding(); 
 
                // Convert the Bytes received to a string and display it on the Server Screen 
                string msg = encoder.GetString(message, 0, bytesRead); 
                WriteMessage(msg); 
 
                // Now Echo the message back 
 
                Echo(msg, encoder, clientStream); 
            } 
 
            tcpClient.Close(); 
        }

 client.Connect(serverEndPoint);

NetworkStream clientStream = client.GetStream(); 
 
            ASCIIEncoding encoder = new ASCIIEncoding(); 
            byte[] buffer = encoder.GetBytes(msg); 
 
            clientStream.Write(buffer, 0, buffer.Length); 
            clientStream.Flush(); 
 
            // Receive the TcpServer.response. 
 
            // Buffer to store the response bytes. 
            Byte[]  data = new Byte[256];

 //字符串存储响应ASCII码表示。 
   

 
            // Read the first batch of the TcpServer response bytes. 
            Int32 bytes = clientStream.Read(data, 0, data.Length); 
            responseData = System.Text.Encoding.ASCII.GetString(data, 0, bytes); 
             
            rtbClient.AppendText(Environment.NewLine + "From Server: " + responseData);