using System;using System.Collections.Generic;using System.Text;using System.Net;using System.Net.Sockets;using System.Threading;namespace AsyncServer{ public class UdpState {  public UdpClient udpClient;  public IPEndPoint ipEndPoint;  public const int BufferSize = 1024;  public byte[] buffer = new byte[BufferSize];  public int counter = 0; } public class AsyncUdpSever {  private IPEndPoint ipEndPoint = null;  private IPEndPoint remoteEP = null;  private UdpClient udpReceive = null;  private UdpClient udpSend = null;  private const int listenPort = 1100;  private const int remotePort = 1101;  UdpState udpReceiveState = null;  UdpState udpSendState = null;  private ManualResetEvent sendDone = new ManualResetEvent(false);  private ManualResetEvent receiveDone = new ManualResetEvent(false);  public AsyncUdpSever()  {   ipEndPoint = new IPEndPoint(IPAddress.Any, listenPort);   remoteEP = new IPEndPoint(Dns.GetHostAddresses(Dns.GetHostName())[0], remotePort);   udpReceive = new UdpClient(ipEndPoint);   udpSend = new UdpClient();   udpReceiveState = new UdpState();      udpReceiveState.udpClient = udpReceive;   udpReceiveState.ipEndPoint = ipEndPoint;   udpSendState = new UdpState();   udpSendState.udpClient = udpSend;   udpSendState.ipEndPoint = remoteEP;  }  public void ReceiveMsg()  {   Console.WriteLine("listening for messages");   while(true)   {    lock (this)    {      IAsyncResult iar = udpReceive.BeginReceive(new AsyncCallback(ReceiveCallback), udpReceiveState);     receiveDone.WaitOne();     Thread.Sleep(100);    }   }  }  private void ReceiveCallback(IAsyncResult iar)  {   UdpState udpReceiveState = iar.AsyncState as UdpState;   if (iar.IsCompleted)   {    Byte[] receiveBytes = udpReceiveState.udpClient.EndReceive(iar, ref udpReceiveState.ipEndPoint);    string receiveString = Encoding.ASCII.GetString(receiveBytes);    Console.WriteLine("Received: {0}", receiveString);    //Thread.Sleep(100);    receiveDone.Set();    SendMsg();   }  }  private void SendMsg()  {   udpSend.Connect(udpSendState.ipEndPoint);   udpSendState.udpClient = udpSend;   udpSendState.counter ++;   string message = string.Format("第{0}個UDP請求處理完成！",udpSendState.counter);   Byte[] sendBytes = Encoding.Unicode.GetBytes(message);   udpSend.BeginSend(sendBytes, sendBytes.Length, new AsyncCallback(SendCallback), udpSendState);   sendDone.WaitOne();  }  private void SendCallback(IAsyncResult iar)  {   UdpState udpState = iar.AsyncState as UdpState;   Console.WriteLine("第{0}個請求處理完畢！", udpState.counter);   Console.WriteLine("number of bytes sent: {0}", udpState.udpClient.EndSend(iar));   sendDone.Set();  }  public static void Main()  {   AsyncUdpSever aus = new AsyncUdpSever();   Thread t = new Thread(new ThreadStart(aus.ReceiveMsg));   t.Start();   Console.Read();  } }}

using System;using System.Collections.Generic;using System.Text;using System.Net;using System.Net.Sockets;using System.Threading;namespace AsyncClient{ public class UdpState {  public UdpClient udpClient = null;  public IPEndPoint ipEndPoint = null;  public const int BufferSize = 1024;  public byte[] buffer = new byte[BufferSize];  public int counter = 0; } public class AsyncUdpClient {  public static bool messageSent = false;  // Receive a message and write it to the console.  private const int listenPort = 1101;  private const int remotePort = 1100;  private IPEndPoint localEP = null;  private IPEndPoint remoteEP = null;  private UdpClient udpReceive = null;  private UdpClient udpSend = null;  private UdpState udpSendState = null;  private UdpState udpReceiveState = null;  private int counter = 0;  private ManualResetEvent sendDone = new ManualResetEvent(false);  private ManualResetEvent receiveDone = new ManualResetEvent(false);  private Socket receiveSocket;  private Socket sendSocket;  public AsyncUdpClient()  {   localEP = new IPEndPoint(IPAddress.Any, listenPort);   remoteEP = new IPEndPoint(Dns.GetHostAddresses(Dns.GetHostName())[0],remotePort);   udpReceive = new UdpClient(localEP);      udpSend = new UdpClient();   udpSendState = new UdpState();   udpSendState.ipEndPoint = remoteEP;   udpSendState.udpClient = udpSend;   udpReceiveState = new UdpState();   udpReceiveState.ipEndPoint = remoteEP;   udpReceiveState.udpClient = udpReceive;   receiveSocket = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);   receiveSocket.Bind(localEP);   sendSocket = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);   sendSocket.Bind(remoteEP);  }  public void SendMsg()  {    udpSend.Connect(remoteEP);   //Thread t = new Thread(new ThreadStart(ReceiveMessages));   //t.Start();   Byte[] sendBytes;   string message;      while (true)   {     message = "Client" + (counter++).ToString();    lock (this)    {     sendBytes = Encoding.ASCII.GetBytes(message);     udpSendState.counter = counter;     udpSend.BeginSend(sendBytes, sendBytes.Length, new AsyncCallback(SendCallback), udpSendState);     sendDone.WaitOne();     Thread.Sleep(200);     ReceiveMessages();    }   }      }  public void SendCallback(IAsyncResult iar)  {   UdpState udpState = iar.AsyncState as UdpState;   if (iar.IsCompleted)   {    Console.WriteLine("第{0}個發送完畢！", udpState.counter);    Console.WriteLine("number of bytes sent: {0}", udpState.udpClient.EndSend(iar));    //if (udpState.counter == 10)    //{    // udpState.udpClient.Close();    //}    sendDone.Set();   }     }  public void ReceiveMessages()  {   lock (this)   {    udpReceive.BeginReceive(new AsyncCallback(ReceiveCallback), udpReceiveState);    receiveDone.WaitOne();    Thread.Sleep(100);   }   }  public void ReceiveCallback(IAsyncResult iar)  {   UdpState udpState = iar.AsyncState as UdpState;   if (iar.IsCompleted)   {    Byte[] receiveBytes = udpState.udpClient.EndReceive(iar, ref udpReceiveState.ipEndPoint);    string receiveString = Encoding.Unicode.GetString(receiveBytes);    Console.WriteLine("Received: {0}", receiveString);    receiveDone.Set();   }     }  public static void Main()  {   AsyncUdpClient auc = new AsyncUdpClient();   auc.SendMsg();   Console.Read();  } }}