using System;using System.Net;using System.Net.Sockets;using System.Threading;using System.Text;// State object for receiving data from remote device.public class StateObject {    // Client socket.    public Socket workSocket = null;    // Size of receive buffer.    public const int BufferSize = 256;    // Receive buffer.    public byte[] buffer = new byte[BufferSize];    // Received data string.    public StringBuilder sb = new StringBuilder();}public class AsynchronousClient {    // The port number for the remote device.    private const int port = 11000;    // ManualResetEvent instances signal completion.    private static ManualResetEvent connectDone =         new ManualResetEvent(false);    private static ManualResetEvent sendDone =         new ManualResetEvent(false);    private static ManualResetEvent receiveDone =         new ManualResetEvent(false);    // The response from the remote device.    private static String response = String.Empty;    private static void StartClient() {        // Connect to a remote device.        try {            // Establish the remote endpoint for the socket.            // The name of the             // remote device is "host.contoso.com".            IPHostEntry ipHostInfo = Dns.Resolve("host.contoso.com");            IPAddress ipAddress = ipHostInfo.AddressList[0];            IPEndPoint remoteEP = new IPEndPoint(ipAddress, port);            // Create a TCP/IP socket.            Socket client = new Socket(AddressFamily.InterNetwork,                SocketType.Stream, ProtocolType.Tcp);            // Connect to the remote endpoint.            client.BeginConnect( remoteEP,                 new AsyncCallback(ConnectCallback), client);            connectDone.WaitOne();            // Send test data to the remote device.            Send(client,"This is a test<EOF>");            sendDone.WaitOne();            // Receive the response from the remote device.            Receive(client);            receiveDone.WaitOne();            // Write the response to the console.            Console.WriteLine("Response received : {0}", response);            // Release the socket.            client.Shutdown(SocketShutdown.Both);            client.Close();                    } catch (Exception e) {            Console.WriteLine(e.ToString());        }    }    private static void ConnectCallback(IAsyncResult ar) {        try {            // Retrieve the socket from the state object.            Socket client = (Socket) ar.AsyncState;            // Complete the connection.            client.EndConnect(ar);            Console.WriteLine("Socket connected to {0}",                client.RemoteEndPoint.ToString());            // Signal that the connection has been made.            connectDone.Set();        } catch (Exception e) {            Console.WriteLine(e.ToString());        }    }    private static void Receive(Socket client) {        try {            // Create the state object.            StateObject state = new StateObject();            state.workSocket = client;            // Begin receiving the data from the remote device.            client.BeginReceive( state.buffer, 0, StateObject.BufferSize, 0,                new AsyncCallback(ReceiveCallback), state);        } catch (Exception e) {            Console.WriteLine(e.ToString());        }    }    private static void ReceiveCallback( IAsyncResult ar ) {        try {            // Retrieve the state object and the client socket             // from the asynchronous state object.            StateObject state = (StateObject) ar.AsyncState;            Socket client = state.workSocket;            // Read data from the remote device.            int bytesRead = client.EndReceive(ar);            if (bytesRead > 0) {                // There might be more data, so store the data received so far.            state.sb.Append(Encoding.ASCII.GetString(state.buffer,0,bytesRead));                // Get the rest of the data.                client.BeginReceive(state.buffer,0,StateObject.BufferSize,0,                    new AsyncCallback(ReceiveCallback), state);            } else {                // All the data has arrived; put it in response.                if (state.sb.Length > 1) {                    response = state.sb.ToString();                }                // Signal that all bytes have been received.                receiveDone.Set();            }        } catch (Exception e) {            Console.WriteLine(e.ToString());        }    }    private static void Send(Socket client, String data) {        // Convert the string data to byte data using ASCII encoding.        byte[] byteData =http://www.mamicode.com/ Encoding.ASCII.GetBytes(data);        // Begin sending the data to the remote device.        client.BeginSend(byteData, 0, byteData.Length, 0,            new AsyncCallback(SendCallback), client);    }    private static void SendCallback(IAsyncResult ar) {        try {            // Retrieve the socket from the state object.            Socket client = (Socket) ar.AsyncState;            // Complete sending the data to the remote device.            int bytesSent = client.EndSend(ar);            Console.WriteLine("Sent {0} bytes to server.", bytesSent);            // Signal that all bytes have been sent.            sendDone.Set();        } catch (Exception e) {            Console.WriteLine(e.ToString());        }    }        public static int Main(String[] args) {        StartClient();        return 0;    }}

using System;using System.Net;using System.Net.Sockets;using System.Text;using System.Threading;// State object for reading client data asynchronouslypublic 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.Resolve(Dns.GetHostName());        IPAddress ipAddress = ipHostInfo.AddressList[0];        IPEndPoint localEndPoint = new IPEndPoint(ipAddress, 11000);        // 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.         int bytesRead = handler.EndReceive(ar);        if (bytesRead > 0) {            // There  might be more data, so store the data received so far.            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 = state.sb.ToString();            if (content.IndexOf("<EOF>") > -1) {                // All the data has been read from the                 // client. Display it on the console.                Console.WriteLine("Read {0} bytes from socket. \n Data : {1}",                    content.Length, content );                // Echo the data back to the client.                Send(handler, content);            } else {                // 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 =http://www.mamicode.com/ 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) {        StartListening();        return 0;    }}