本文介绍

UdpClient 类在同步阻塞模式中为发送和接收无连接的 UDP 数据包而提供了简单的方法。因为 UDP 是一种无连接的传输协议，所以你不需要在发送和接收数据之前建立任何远程主机连接。你只需要按照下列方式来建立默认的远程主机选项：
使用远程主机名称和端口号作为参数来创建 UdpClient 类的实例。
创建 UdpClient 类的实例然后调用 Connect 方法。
你可以使用任何由 UdpClient 所提供的发送方法把数据发送给远程设备。然后使用 Receive 方法来接收来自于远程主机的数据。
提示：如果你已经指定了一个默认的远程主机，就不要使用主机名称或者 IPEndPoint 来调用 Send 方法。如果你这样做，那么 UdpClient 将会抛出一个异常。

UdpClient 方法同样允许你发送和接收多点传送的数据包。而使用 JoinMulticastGroup 方法可以把 UdpClient 订阅到多点传送分组。也可以使用 DropMulticastGroup 方法把 UdpClient 从多点传送分组的订阅中取消。

本节介绍使用UdpClient实现一个同步的UDP服务器

UdpClient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.Listener.Synchronous
{
    /// <summary>
    /// UdpClient 实现同步UDP服务器
    /// </summary>
    public class UDPServer
    {
        #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>
        /// 服务器使用的异步UdpClient
        /// </summary>
        private UdpClient _server;

        /// <summary>
        /// 客户端会话列表
        /// </summary>
        //private List<UDPState> _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>
        /// 同步UdpClient UDP服务器
        /// </summary>
        /// <param name="listenPort">监听的端口</param>
        public UDPServer(int listenPort)
            : this(IPAddress.Any, listenPort,1024)
        {
        }

        /// <summary>
        /// 同步UdpClient UDP服务器
        /// </summary>
        /// <param name="localEP">监听的终结点</param>
        public UDPServer(IPEndPoint localEP)
            : this(localEP.Address, localEP.Port,1024)
        {
        }

        /// <summary>
        /// 同步UdpClient 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 UDPServer(IPAddress localIPAddress, int listenPort, int maxClient)
        {
            this.Address = localIPAddress;
            this.Port = listenPort;
            this.Encoding = Encoding.Default;

            _maxClient = maxClient;
            //_clients = new List<AsyncUDPSocketState>();
            _server = new UdpClient(new IPEndPoint(this.Address, this.Port));

            _recvBuffer=new byte[_server.Client.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;
                _server.EnableBroadcast = true;
                new Thread(ReceiveData).Start();
            }
        }

        /// <summary>
        /// 停止服务器
        /// </summary>
        public void Stop()
        {
            if (IsRunning)
            {
                IsRunning = false;
                _server.Close();
                //TODO 关闭对所有客户端的连接

            }
        }

        /// <summary>
        /// 同步接收数据的方法
        /// </summary>
        /// <param name="ar"></param>
        private void ReceiveData()
        {
            IPEndPoint remote = null;
            while (true)
            {
                byte[] buffer = null;
                try
                {
                    buffer = _server.Receive(ref remote);
                }
                catch (Exception)
                {
                    //异常处理操作
                    return;
                }
                if (buffer == null || buffer.Length == 0) return;
                //TODO 数据包收到触发事件
                RaiseDataReceived(null);
            }
        }

        /// <summary>
        /// 同步发送数据
        /// </summary>
        /// <param name="msg"></param>
        /// <param name="remote"></param>
        public void Send(string msg, IPEndPoint remote)
        {
            byte[] data = Encoding.Default.GetBytes(msg);
            try
            {
                _server.Send(data, data.Length, remote);
            }
            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<UDPEventArgs> DataReceived;

        private void RaiseDataReceived(UDPState state)
        {
            if (DataReceived != null)
            {
                DataReceived(this, new UDPEventArgs(state));
            }
        }

        /// <summary>
        /// 数据发送完毕事件
        /// </summary>
        public event EventHandler<UDPEventArgs> CompletedSend;

        /// <summary>
        /// 触发数据发送完毕的事件
        /// </summary>
        /// <param name="state"></param>
        private void RaiseCompletedSend(UDPState state)
        {
            if (CompletedSend != null)
            {
                CompletedSend(this, new UDPEventArgs(state));
            }
        }

        /// <summary>
        /// 网络错误事件
        /// </summary>
        public event EventHandler<UDPEventArgs> NetError;
        /// <summary>
        /// 触发网络错误事件
        /// </summary>
        /// <param name="state"></param>
        private void RaiseNetError(UDPState state)
        {
            if (NetError != null)
            {
                NetError(this, new UDPEventArgs(state));
            }
        }

        /// <summary>
        /// 异常事件
        /// </summary>
        public event EventHandler<UDPEventArgs> OtherException;
        /// <summary>
        /// 触发异常事件
        /// </summary>
        /// <param name="state"></param>
        private void RaiseOtherException(UDPState state, string descrip)
        {
            if (OtherException != null)
            {
                OtherException(this, new UDPEventArgs(descrip, state));
            }
        }
        private void RaiseOtherException(UDPState 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(UDPState 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 (AsyncUDPSocketState 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 (_server != null)
                        {
                            _server = null;
                        }
                    }
                    catch (SocketException)
                    {
                        //TODO
                        RaiseOtherException(null);
                    }
                }
                disposed = true;
            }
        }
        #endregion
    }
}

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用户状态封装类

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Net.Sockets;
using System.Net;

namespace NetFrame.Net.UDP.Listener.Synchronous
{
    public class UDPState
    {
        // Client   socket.
        public UdpClient udpClient = 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 IPEndPoint remote = new IPEndPoint(IPAddress.Any, 0);
    }
}

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服务器事件参数类

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace NetFrame.Net.UDP.Listener.Synchronous
{
    /// <summary>
    /// UdpClient 同步UDP服务器事件类
    /// </summary>
    public class UDPEventArgs : EventArgs
    {
        /// <summary>
        /// 提示信息
        /// </summary>
        public string _msg;

        /// <summary>
        /// 客户端状态封装类
        /// </summary>
        public UDPState _state;

        /// <summary>
        /// 是否已经处理过了
        /// </summary>
        public bool IsHandled { get; set; }

        public UDPEventArgs(string msg)
        {
            this._msg = msg;
            IsHandled = false;
        }
        public UDPEventArgs(UDPState state)
        {
            this._state = state;
            IsHandled = false;
        }
        public UDPEventArgs(string msg, UDPState state)
        {
            this._msg = msg;
            this._state = state;
            IsHandled = false;
        }
    }
}

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