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本文介绍在.Net中，System.Net.Sockets 命名空间为需要严密控制网络访问的开发人员提供了 Windows Sockets (Winsock) 接口的托管实现。System.Net 命名空间中的所有其他网络访问类都建立在该套接字Socket实现之上，如TCPClient、TCPListener 和 UDPClient 类封装有关创建到 Internet 的 TCP 和 UDP 连接的详细信息；NetworkStream类则提供用于网络访问的基础数据流等，常见的许多Internet服务都可以见到Socket的踪影，如Telnet、Http、Email、Echo等，这些服务尽管通讯协议Protocol的定义不同，但是其基础的传输都是采用的Socket。 其实，Socket可以象流Stream一样被视为一个数据通道，这个通道架设在应用程序端（客户端）和远程服务器端之间，而后，数据的读取（接收）和写入（发送）均针对这个通道来进行。可见，在应用程序端或者服务器端创建了Socket对象之后，就可以使用Send/SentTo方法将数据发送到连接的Socket,或者使用Receive/ReceiveFrom方法接收来自连接Socket的数据；针对Socket编程，.NET 框架的 Socket 类是 Winsock32 API 提供的套接字服务的托管代码版本。其中为实现网络编程提供了大量的方法，大多数情况下，Socket 类方法只是将数据封送到它们的本机 Win32 副本中并处理任何必要的安全检查。如果你熟悉Winsock API函数，那么用Socket类编写网络程序会非常容易，当然，如果你不曾接触过，也不会太困难，跟随下面的解说，你会发觉使用Socket类开发windows 网络应用程序原来有规可寻，，它们在大多数情况下遵循大致相同的步骤。
本节介绍使用Socket来实现一个同步的UDP服务器。
Socket同步UDP服务器
using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Net.Sockets;using System.Net;using System.Threading;namespace NetFrame.Net.UDP.Sock.Synchronous{/// <summary>/// Socket 实现同步UDP服务器/// </summary>public class SocketUDPServer{#region Fields/// <summary>/// 服务器程序允许的最大客户端连接数/// </summary>private int _maxClient;/// <summary>/// 当前的连接的客户端数/// </summary>private int _clientCount;/// <summary>/// 服务器使用的同步socket/// </summary>private Socket _serverSock;/// <summary>/// 客户端会话列表/// </summary>private List<SocketUDPState> _clients;private bool disposed = false;/// <summary>/// 数据接受缓冲区/// </summary>private byte[] _recvBuffer;#endregion#region Properties/// <summary>/// 服务器是否正在运行/// </summary>public bool IsRunning { get; private set; }/// <summary>/// 监听的IP地址/// </summary>public IPAddress Address { get; private set; }/// <summary>/// 监听的端口/// </summary>public int Port { get; private set; }/// <summary>/// 通信使用的编码/// </summary>public Encoding Encoding { get; set; }#endregion#region 构造函数/// <summary>/// 异步Socket UDP服务器/// </summary>/// <param name="listenPort">监听的端口</param>public SocketUDPServer(int listenPort): this(IPAddress.Any, listenPort,1024){}/// <summary>/// 异步Socket UDP服务器/// </summary>/// <param name="localEP">监听的终结点</param>public SocketUDPServer(IPEndPoint localEP): this(localEP.Address, localEP.Port,1024){}/// <summary>/// 异步Socket UDP服务器/// </summary>/// <param name="localIPAddress">监听的IP地址</param>/// <param name="listenPort">监听的端口</param>/// <param name="maxClient">最大客户端数量</param>public SocketUDPServer(IPAddress localIPAddress, int listenPort, int maxClient){this.Address = localIPAddress;this.Port = listenPort;this.Encoding = Encoding.Default;_maxClient = maxClient;_clients = new List<SocketUDPState>();_serverSock = new Socket(localIPAddress.AddressFamily, SocketType.Dgram, ProtocolType.Udp);_recvBuffer=new byte[_serverSock.ReceiveBufferSize];}#endregion#region Method/// <summary>/// 启动服务器/// </summary>/// <returns>异步TCP服务器</returns>public void Start(){if (!IsRunning){IsRunning = true;_serverSock.Bind(new IPEndPoint(this.Address, this.Port));//启动一个线程监听数据new Thread(ReceiveData).Start();}}/// <summary>/// 停止服务器/// </summary>public void Stop(){if (IsRunning){IsRunning = false;_serverSock.Close();//TODO 关闭对所有客户端的连接CloseAllClient();}}/// <summary>/// 同步数据接收方法/// </summary>private void ReceiveData(){int len = -1;EndPoint remote = null;while (true){try{len = _serverSock.ReceiveFrom(_recvBuffer, ref remote);//if (!_clients.Contains(remote))//{// _clients.Add(remote);//}}catch (Exception){//TODO 异常处理操作RaiseOtherException(null);}}}/// <summary>/// 同步发送数据/// </summary>public void Send(string msg, EndPoint clientip){byte[] data = Encoding.Default.GetBytes(msg);try{_serverSock.SendTo(data, clientip);//数据发送完成事件RaiseCompletedSend(null);}catch (Exception){//TODO 异常处理RaiseOtherException(null);}}#endregion#region 事件/// <summary>/// 接收到数据事件/// </summary>public event EventHandler<SocketUDPEventArgs> DataReceived;private void RaiseDataReceived(SocketUDPState state){if (DataReceived != null){DataReceived(this, new SocketUDPEventArgs(state));}}/// <summary>/// 数据发送完毕事件/// </summary>public event EventHandler<SocketUDPEventArgs> CompletedSend;/// <summary>/// 触发数据发送完毕的事件/// </summary>/// <param name="state"></param>private void RaiseCompletedSend(SocketUDPState state){if (CompletedSend != null){CompletedSend(this, new SocketUDPEventArgs(state));}}/// <summary>/// 网络错误事件/// </summary>public event EventHandler<SocketUDPEventArgs> NetError;/// <summary>/// 触发网络错误事件/// </summary>/// <param name="state"></param>private void RaiseNetError(SocketUDPState state){if (NetError != null){NetError(this, new SocketUDPEventArgs(state));}}/// <summary>/// 异常事件/// </summary>public event EventHandler<SocketUDPEventArgs> OtherException;/// <summary>/// 触发异常事件/// </summary>/// <param name="state"></param>private void RaiseOtherException(SocketUDPState state, string descrip){if (OtherException != null){OtherException(this, new SocketUDPEventArgs(descrip, state));}}private void RaiseOtherException(SocketUDPState state){RaiseOtherException(state, "");}#endregion#region Close/// <summary>/// 关闭一个与客户端之间的会话/// </summary>/// <param name="state">需要关闭的客户端会话对象</param>public void Close(SocketUDPState state){if (state != null){_clients.Remove(state);_clientCount–;//TODO 触发关闭事件}}/// <summary>/// 关闭所有的客户端会话,与所有的客户端连接会断开/// </summary>public void CloseAllClient(){foreach (SocketUDPState client in _clients){Close(client);}_clientCount = 0;_clients.Clear();}#endregion#region 释放/// <summary>/// Performs application-defined tasks associated with freeing,/// releasing, or resetting unmanaged resources./// </summary>public void Dispose(){Dispose(true);GC.SuppressFinalize(this);}/// <summary>/// Releases unmanaged and – optionally – managed resources/// </summary>/// <param name="disposing"><c>true</c> to release/// both managed and unmanaged resources; <c>false</c>/// to release only unmanaged resources.</param>protected virtual void Dispose(bool disposing){if (!this.disposed){if (disposing){try{Stop();if (_serverSock != null){_serverSock = null;}}catch (SocketException){//TODORaiseOtherException(null);}}disposed = true;}}#endregion}}客户状态封装类
带上心灵去旅行，以平和的心态看待一切，
