using System; using System.Text; using System.Net; using System.Net.Sockets; namespace Client {     class Program     {         //客户端 Socket对象         private static Socket clientSocket;         //服务器端 终点         private static EndPoint epServer;         //接收数据的字符数组         private static byte[] receiveData;         public static void Main(string[] args)         {             //客户端Socket对象实例化             clientSocket = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);             //设置服务器端IP地址和对应端口             IPEndPoint server = new IPEndPoint(IPAddress.Parse("192.168.1.165"), 11000);             //实例化服务器端 终点             epServer = (EndPoint)server;             string msg;     //要发送的消息             byte[] sendData;    //要发送的字符串             while (true) {                 msg = Console.ReadLine();   //输入要发送的消息                 if (msg == "exit") break;   //当输入“exit”时，退出客户端程序                 //将消息通过ASCII编码转换为字符数组，                 //如果要发送汉字或其他特殊符号，可以采用UTF-8                 sendData = Encoding.ASCII.GetBytes(msg);                    //开始异步发送消息                 //参数：sendData           要发送的数据                 //参数：0：                 要发送数据的起始位置                 //参数：sendData.Length：   要发送数据的字节数                 //参数：SocketFlags.None：  按位组合方式                 //参数：epServer：          接收方设备（包含IP和端口）                 //参数：new AsyncCallback(SendData):   委托                 //参数：null：          请求的状态信息                 clientSocket.BeginSendTo(sendData, 0, sendData.Length, SocketFlags.None,                     epServer, new AsyncCallback(SendData), null);                 //实例化接收数据的字符数组                 //若在声明时已经初始化，此处依然要进行重新初始化                 //当上次接收的数据长度大于本次，则该数组里包含上次接收的残留数据                 //比如：上次接收“你个小逗逼”。本次接收“开玩笑”。                 //则数组中的数据为：“开玩笑逗逼”。                 receiveData = new byte[1024];                 //开始异步接收消息                 //参数部分与异步发送部分对应，基本一致                 clientSocket.BeginReceiveFrom(receiveData, 0, receiveData.Length, SocketFlags.None,                     ref epServer, new AsyncCallback(ReceiveData), null);             }         }         //异步发送消息的委托函数         private static void SendData(IAsyncResult iar)         {             //完成异步发送             clientSocket.EndSend(iar);         }         //异步接收消息的委托函数         private static void ReceiveData(IAsyncResult iar)         {             //完成异步接收  recv 表示接收到的字节数             int recv = clientSocket.EndReceive(iar);             //将接收到的数据打印出来             Console.WriteLine("Server: " + Encoding.ASCII.GetString(receiveData, 0, recv));         }     } }

using System; using System.Text; using System.Net; using System.Net.Sockets; namespace Server {     class AsyncUdpServer     {         //服务器端Socket对象         private static Socket serverSocket;         //接收数据的字符数组         private static byte[] receiveData = new byte[1024];         public static void Main(string[] args)         {             //实例化服务器端Socket对象             serverSocket = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);             //服务器端的IP和端口，IPAddress.Any实际是：0.0.0.0，表示任意，基本上表示本机IP             IPEndPoint server = new IPEndPoint(IPAddress.Any, 11000);             //Socket对象跟服务器端的IP和端口绑定             serverSocket.Bind(server);             //客户端的IP和端口，端口 0 表示任意端口             IPEndPoint clients = new IPEndPoint(IPAddress.Any, 0);             //实例化客户端 终点             EndPoint epSender = (EndPoint)clients;             //开始异步接收消息  接收后，epSender存储的是发送方的IP和端口             serverSocket.BeginReceiveFrom(receiveData, 0, receiveData.Length, SocketFlags.None,                 ref epSender, new AsyncCallback(ReceiveData), epSender);             Console.WriteLine("Listening...");             Console.ReadLine();         }         private static void SendData(IAsyncResult iar)         {             serverSocket.EndSend(iar);         }         private static void ReceiveData(IAsyncResult iar)         {             //客户端的IP和端口，端口 0 表示任意端口             IPEndPoint client = new IPEndPoint(IPAddress.Any, 0);             //实例化客户端 终点             EndPoint epSender = (EndPoint)client;             //结束异步接收消息  recv 表示接收到的字符数             int recv = serverSocket.EndReceiveFrom(iar, ref epSender);                        //将接收到的数据打印出来，发送方采用什么编码方式，此处就采用什么编码方式 转换成字符串             Console.WriteLine("Client:" + Encoding.ASCII.GetString(receiveData, 0, recv));             //定义要发送回客户端的消息，采用ASCII编码，             //如果要发送汉字或其他特殊符号，可以采用UTF-8                        byte[] sendData = Encoding.ASCII.GetBytes("hello");             //开始异步发送消息  epSender是上次接收消息时的客户端IP和端口信息             serverSocket.BeginSendTo(sendData, 0, sendData.Length, SocketFlags.None,                 epSender, new AsyncCallback(SendData), epSender);             //重新实例化接收数据字节数组             receiveData = new byte[1024];             //开始异步接收消息，此处的委托函数是这个函数本身，递归             serverSocket.BeginReceiveFrom(receiveData, 0, receiveData.Length, SocketFlags.None,                 ref epSender, new AsyncCallback(ReceiveData), epSender);         }     } }