C#高性能Socket服务器IOCP实现

引言
我一直在探寻一个高性能的Socket客户端代码。以前，我使用Socket类写了一些基于传统异步编程模型的代码（BeginSend、BeginReceive，等等）

也看过很多博客的知识，在linux中有poll和epoll来实现，在windows下面

微软MSDN中也提供了SocketAsyncEventArgs这个类来实现IOCP

地址:https://msdn.microsoft.com/zh-cn/library/system.net.sockets.socketasynceventargs.aspx

NET Framework中的APM也称为Begin/End模式。这是因为会调用Begin方法来启动异步操作，然后返回一个IAsyncResult 对象。可以选择将一个代理作为参数提供给Begin方法，异步操作完成时会调用该方法。或者，一个线程可以等待 IAsyncResult.AsyncWaitHandle。当回调被调用或发出等待信号时，就会调用End方法来获取异步操作的结果。这种模式很灵活，使用相对简单，在 .NET Framework 中非常常见。
但是，您必须注意，如果进行大量异步套接字操作，是要付出代价的。针对每次操作，都必须创建一个IAsyncResult对象，而且该对象不能被重复使用。由于大量使用对象分配和垃圾收集，这会影响性能。为了解决这个问题，新版本提供了另一个使用套接字上执行异步I/O的方法模式。这种新模式并不要求为每个套接字操作分配操作上下文对象。

代码下载：http://download.csdn.net/detail/zhujunxxxxx/8431289 这里的代码优化了的
目标
在上面微软提供的例子我觉得不是很完整，没有具体一个流程，只是受到客户端消息后发送相同内容给客户端，初学者不容易看懂流程，因为我花了一天的时间来实现一个功能齐全的IOCP服务器，

效果如下

代码

首先是ICOPServer.cs 这个类是IOCP服务器的核心类，目前这个类是网络上比较全的代码，MSDN上面的例子都没有我的全

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

namespace ServerTest
{
    /// <summary>
    /// IOCP SOCKET服务器
    /// </summary>
    public class IOCPServer : IDisposable
    {
        const int opsToPreAlloc = 2;
        #region Fields
        /// <summary>
        /// 服务器程序允许的最大客户端连接数
        /// </summary>
        private int _maxClient;

        /// <summary>
        /// 监听Socket，用于接受客户端的连接请求
        /// </summary>
        private Socket _serverSock;

        /// <summary>
        /// 当前的连接的客户端数
        /// </summary>
        private int _clientCount;

        /// <summary>
        /// 用于每个I/O Socket操作的缓冲区大小
        /// </summary>
        private int _bufferSize = 1024;

        /// <summary>
        /// 信号量
        /// </summary>
        Semaphore _maxAcceptedClients;

        /// <summary>
        /// 缓冲区管理
        /// </summary>
        BufferManager _bufferManager;

        /// <summary>
        /// 对象池
        /// </summary>
        SocketAsyncEventArgsPool _objectPool;

        private bool disposed = false;

        #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 Ctors

        /// <summary>
        /// 异步IOCP SOCKET服务器
        /// </summary>
        /// <param name="listenPort">监听的端口</param>
        /// <param name="maxClient">最大的客户端数量</param>
        public IOCPServer(int listenPort, int maxClient)
        : this(IPAddress.Any, listenPort, maxClient)
        {
        }

        /// <summary>
        /// 异步Socket TCP服务器
        /// </summary>
        /// <param name="localEP">监听的终结点</param>
        /// <param name="maxClient">最大客户端数量</param>
        public IOCPServer(IPEndPoint localEP, int maxClient)
        : this(localEP.Address, localEP.Port, maxClient)
        {
        }

        /// <summary>
        /// 异步Socket TCP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 IOCPServer(IPAddress localIPAddress, int listenPort, int maxClient)
        {
            this.Address = localIPAddress;
            this.Port = listenPort;
            this.Encoding = Encoding.Default;

            _maxClient = maxClient;

            _serverSock = new Socket(localIPAddress.AddressFamily, SocketType.Stream, ProtocolType.Tcp);

            _bufferManager = new BufferManager(_bufferSize * _maxClient * opsToPreAlloc, _bufferSize);

            _objectPool = new SocketAsyncEventArgsPool(_maxClient);

            _maxAcceptedClients = new Semaphore(_maxClient, _maxClient);
        }

        #endregion


        #region 初始化

        /// <summary>
        /// 初始化函数
        /// </summary>
        public void Init()
        {
            // Allocates one large byte buffer which all I/O operations use a piece of. This gaurds 
            // against memory fragmentation
            _bufferManager.InitBuffer();

            // preallocate pool of SocketAsyncEventArgs objects
            SocketAsyncEventArgs readWriteEventArg;

            for (int i = 0; i < _maxClient; i++)
            {
                //Pre-allocate a set of reusable SocketAsyncEventArgs
                readWriteEventArg = new SocketAsyncEventArgs();
                readWriteEventArg.Completed += new EventHandler<SocketAsyncEventArgs>(OnIOCompleted);
                readWriteEventArg.UserToken = null;

                // assign a byte buffer from the buffer pool to the SocketAsyncEventArg object
                _bufferManager.SetBuffer(readWriteEventArg);

                // add SocketAsyncEventArg to the pool
                _objectPool.Push(readWriteEventArg);
            }

        }

        #endregion

        #region Start
        /// <summary>
        /// 启动
        /// </summary>
        public void Start()
        {
            if (!IsRunning)
            {
                Init();
                IsRunning = true;
                IPEndPoint localEndPoint = new IPEndPoint(Address, Port);
                // 创建监听socket
                _serverSock = new Socket(localEndPoint.AddressFamily, SocketType.Stream, ProtocolType.Tcp);
                //_serverSock.ReceiveBufferSize = _bufferSize;
                //_serverSock.SendBufferSize = _bufferSize;
                if (localEndPoint.AddressFamily == AddressFamily.InterNetworkV6)
                {
                    // 配置监听socket为 dual-mode (IPv4 & IPv6) 
                    // 27 is equivalent to IPV6_V6ONLY socket option in the winsock snippet below,
                    _serverSock.SetSocketOption(SocketOptionLevel.IPv6, (SocketOptionName)27, false);
                    _serverSock.Bind(new IPEndPoint(IPAddress.IPv6Any, localEndPoint.Port));
                }
                else
                {
                    _serverSock.Bind(localEndPoint);
                }
                // 开始监听
                _serverSock.Listen(this._maxClient);
                // 在监听Socket上投递一个接受请求。
                StartAccept(null);
            }
        }
        #endregion

        #region Stop

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

            }
        }

        #endregion


        #region Accept

        /// <summary>
        /// 从客户端开始接受一个连接操作
        /// </summary>
        private void StartAccept(SocketAsyncEventArgs asyniar)
        {
            if (asyniar == null)
            {
                asyniar = new SocketAsyncEventArgs();
                asyniar.Completed += new EventHandler<SocketAsyncEventArgs>(OnAcceptCompleted);
            }
            else
            {
                //socket must be cleared since the context object is being reused
                asyniar.AcceptSocket = null;
            }
            _maxAcceptedClients.WaitOne();
            if (!_serverSock.AcceptAsync(asyniar))
            {
                ProcessAccept(asyniar);
                //如果I/O挂起等待异步则触发AcceptAsyn_Asyn_Completed事件
                //此时I/O操作同步完成，不会触发Asyn_Completed事件，所以指定BeginAccept()方法
            }
        }

        /// <summary>
        /// accept 操作完成时回调函数
        /// </summary>
        /// <param name="sender">Object who raised the event.</param>
        /// <param name="e">SocketAsyncEventArg associated with the completed accept operation.</param>
        private void OnAcceptCompleted(object sender, SocketAsyncEventArgs e)
        {
            ProcessAccept(e);
        }

        /// <summary>
        /// 监听Socket接受处理
        /// </summary>
        /// <param name="e">SocketAsyncEventArg associated with the completed accept operation.</param>
        private void ProcessAccept(SocketAsyncEventArgs e)
        {
            if (e.SocketError == SocketError.Success)
            {
                Socket s = e.AcceptSocket;//和客户端关联的socket
                if (s.Connected)
                {
                    try
                    {

                        Interlocked.Increment(ref _clientCount);//原子操作加1
                        SocketAsyncEventArgs asyniar = _objectPool.Pop();
                        asyniar.UserToken = s;

                        Log4Debug(String.Format("客户 {0} 连入, 共有 {1} 个连接。", s.RemoteEndPoint.ToString(), _clientCount));

                        if (!s.ReceiveAsync(asyniar))//投递接收请求
                        {
                            ProcessReceive(asyniar);
                        }
                    }
                    catch (SocketException ex)
                    {
                        Log4Debug(String.Format("接收客户 {0} 数据出错, 异常信息： {1} 。", s.RemoteEndPoint, ex.ToString()));
                        //TODO 异常处理
                    }
                    //投递下一个接受请求
                    StartAccept(e);
                }
            }
        }

        #endregion

        #region 发送数据

        /// <summary>
        /// 异步的发送数据
        /// </summary>
        /// <param name="e"></param>
        /// <param name="data"></param>
        public void Send(SocketAsyncEventArgs e, byte[] data)
        {
            if (e.SocketError == SocketError.Success)
            {
                Socket s = e.AcceptSocket;//和客户端关联的socket
                if (s.Connected)
                {
                    Array.Copy(data, 0, e.Buffer, 0, data.Length);//设置发送数据

                    //e.SetBuffer(data, 0, data.Length); //设置发送数据
                    if (!s.SendAsync(e))//投递发送请求，这个函数有可能同步发送出去，这时返回false，并且不会引发SocketAsyncEventArgs.Completed事件
                    {
                        // 同步发送时处理发送完成事件
                        ProcessSend(e);
                    }
                    else
                    {
                        CloseClientSocket(e);
                    }
                }
            }
        }

        /// <summary>
        /// 同步的使用socket发送数据
        /// </summary>
        /// <param name="socket"></param>
        /// <param name="buffer"></param>
        /// <param name="offset"></param>
        /// <param name="size"></param>
        /// <param name="timeout"></param>
        public void Send(Socket socket, byte[] buffer, int offset, int size, int timeout)
        {
            socket.SendTimeout = 0;
            int startTickCount = Environment.TickCount;
            int sent = 0; // how many bytes is already sent
            do
            {
                if (Environment.TickCount > startTickCount + timeout)
                {
                    //throw new Exception("Timeout.");
                }
                try
                {
                    sent += socket.Send(buffer, offset + sent, size - sent, SocketFlags.None);
                }
                catch (SocketException ex)
                {
                    if (ex.SocketErrorCode == SocketError.WouldBlock ||
                    ex.SocketErrorCode == SocketError.IOPending ||
                    ex.SocketErrorCode == SocketError.NoBufferSpaceAvailable)
                    {
                        // socket buffer is probably full, wait and try again
                        Thread.Sleep(30);
                    }
                    else
                    {
                        throw ex; // any serious error occurr
                    }
                }
            } while (sent < size);
        }


        /// <summary>
        /// 发送完成时处理函数
        /// </summary>
        /// <param name="e">与发送完成操作相关联的SocketAsyncEventArg对象</param>
        private void ProcessSend(SocketAsyncEventArgs e)
        {
            if (e.SocketError == SocketError.Success)
            {
                Socket s = (Socket)e.UserToken;

                //TODO
            }
            else
            {
                CloseClientSocket(e);
            }
        }

        #endregion

        #region 接收数据


        /// <summary>
        ///接收完成时处理函数
        /// </summary>
        /// <param name="e">与接收完成操作相关联的SocketAsyncEventArg对象</param>
        private void ProcessReceive(SocketAsyncEventArgs e)
        {
            if (e.SocketError == SocketError.Success)//if (e.BytesTransferred > 0 && e.SocketError == SocketError.Success)
            {
                // 检查远程主机是否关闭连接
                if (e.BytesTransferred > 0)
                {
                    Socket s = (Socket)e.UserToken;
                    //判断所有需接收的数据是否已经完成
                    if (s.Available == 0)
                    {
                        //从侦听者获取接收到的消息。 
                        //String received = Encoding.ASCII.GetString(e.Buffer, e.Offset, e.BytesTransferred);
                        //echo the data received back to the client
                        //e.SetBuffer(e.Offset, e.BytesTransferred);

                        byte[] data = new byte[e.BytesTransferred];
                        Array.Copy(e.Buffer, e.Offset, data, 0, data.Length);//从e.Buffer块中复制数据出来，保证它可重用

                        string info = Encoding.Default.GetString(data);
                        Log4Debug(String.Format("收到 {0} 数据为 {1}", s.RemoteEndPoint.ToString(), info));
                        //TODO 处理数据

                        //增加服务器接收的总字节数。
                    }

                    if (!s.ReceiveAsync(e))//为接收下一段数据，投递接收请求，这个函数有可能同步完成，这时返回false，并且不会引发SocketAsyncEventArgs.Completed事件
                    {
                        //同步接收时处理接收完成事件
                        ProcessReceive(e);
                    }
                }
            }
            else
            {
                CloseClientSocket(e);
            }
        }

        #endregion

        #region 回调函数

        /// <summary>
        /// 当Socket上的发送或接收请求被完成时，调用此函数
        /// </summary>
        /// <param name="sender">激发事件的对象</param>
        /// <param name="e">与发送或接收完成操作相关联的SocketAsyncEventArg对象</param>
        private void OnIOCompleted(object sender, SocketAsyncEventArgs e)
        {
            // Determine which type of operation just completed and call the associated handler.
            switch (e.LastOperation)
            {
                case SocketAsyncOperation.Accept:
                    ProcessAccept(e);
                    break;
                case SocketAsyncOperation.Receive:
                    ProcessReceive(e);
                    break;
                default:
                    throw new ArgumentException("The last operation completed on the socket was not a receive or send");
            }
        }

        #endregion

        #region Close
        /// <summary>
        /// 关闭socket连接
        /// </summary>
        /// <param name="e">SocketAsyncEventArg associated with the completed send/receive operation.</param>
        private void CloseClientSocket(SocketAsyncEventArgs e)
        {
            Log4Debug(String.Format("客户 {0} 断开连接!", ((Socket)e.UserToken).RemoteEndPoint.ToString()));
            Socket s = e.UserToken as Socket;
            CloseClientSocket(s, e);
        }

        /// <summary>
        /// 关闭socket连接
        /// </summary>
        /// <param name="s"></param>
        /// <param name="e"></param>
        private void CloseClientSocket(Socket s, SocketAsyncEventArgs e)
        {
            try
            {
                s.Shutdown(SocketShutdown.Send);
            }
            catch (Exception)
            {
                // Throw if client has closed, so it is not necessary to catch.
            }
            finally
            {
                s.Close();
            }
            Interlocked.Decrement(ref _clientCount);
            _maxAcceptedClients.Release();
            _objectPool.Push(e);//SocketAsyncEventArg 对象被释放，压入可重用队列。
        }
        #endregion

        #region Dispose
        /// <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 ex)
                    {
                        //TODO 事件
                    }
                }
                disposed = true;
            }
        }
        #endregion

        public void Log4Debug(string msg)
        {
            Console.WriteLine("notice:" + msg);
        }

    }
}

BufferManager.cs 这个类是缓存管理类，是采用MSDN上面的例子一样的 地址: https://msdn.microsoft.com/zh-cn/library/bb517542.aspx

官网地址：https://docs.microsoft.com/zh-cn/dotnet/api/system.servicemodel.channels.buffermanager?view=netframework-4.5

class BufferManager  
    {  
        int m_numBytes;                 // the total number of bytes controlled by the buffer pool  
        byte[] m_buffer;                // the underlying byte array maintained by the Buffer Manager  
        Stack<int> m_freeIndexPool;     //   
        int m_currentIndex;  
        int m_bufferSize;  
  
        public BufferManager(int totalBytes, int bufferSize)  
        {  
            m_numBytes = totalBytes;  
            m_currentIndex = 0;  
            m_bufferSize = bufferSize;  
            m_freeIndexPool = new Stack<int>();  
        }  
  
        // Allocates buffer space used by the buffer pool  
        public void InitBuffer()  
        {  
            // create one big large buffer and divide that   
            // out to each SocketAsyncEventArg object  
            m_buffer = new byte[m_numBytes];  
        }  
  
        // Assigns a buffer from the buffer pool to the   
        // specified SocketAsyncEventArgs object  
        //  
        // <returns>true if the buffer was successfully set, else false</returns>  
        public bool SetBuffer(SocketAsyncEventArgs args)  
        {  
  
            if (m_freeIndexPool.Count > 0)  
            {  
                args.SetBuffer(m_buffer, m_freeIndexPool.Pop(), m_bufferSize);  
            }  
            else  
            {  
                if ((m_numBytes - m_bufferSize) < m_currentIndex)  
                {  
                    return false;  
                }  
                args.SetBuffer(m_buffer, m_currentIndex, m_bufferSize);  
                m_currentIndex += m_bufferSize;  
            }  
            return true;  
        }  
  
        // Removes the buffer from a SocketAsyncEventArg object.    
        // This frees the buffer back to the buffer pool  
        public void FreeBuffer(SocketAsyncEventArgs args)  
        {  
            m_freeIndexPool.Push(args.Offset);  
            args.SetBuffer(null, 0, 0);  
        }  
    }

SocketAsyncEventArgsPool.cs 这个类也是来自MSDN的 地址:https://msdn.microsoft.com/zh-cn/library/system.net.sockets.socketasynceventargs.aspx

    // Represents a collection of reusable SocketAsyncEventArgs objects.  
    public class SocketAsyncEventArgsPool
    {
        Stack<SocketAsyncEventArgs> m_pool;

        // Initializes the object pool to the specified size
        //
        // The "capacity" parameter is the maximum number of 
        // SocketAsyncEventArgs objects the pool can hold
        public SocketAsyncEventArgsPool(int capacity)
        {
            m_pool = new Stack<SocketAsyncEventArgs>(capacity);
        }

        // Add a SocketAsyncEventArg instance to the pool
        //
        //The "item" parameter is the SocketAsyncEventArgs instance 
        // to add to the pool
        public void Push(SocketAsyncEventArgs item)
        {
            if (item == null) { throw new ArgumentNullException("Items added to a SocketAsyncEventArgsPool cannot be null"); }
            lock (m_pool)
            {
                m_pool.Push(item);
            }
        }

        // Removes a SocketAsyncEventArgs instance from the pool
        // and returns the object removed from the pool
        public SocketAsyncEventArgs Pop()
        {
            lock (m_pool)
            {
                return m_pool.Pop();
            }
        }

        // The number of SocketAsyncEventArgs instances in the pool
        public int Count
        {
            get { return m_pool.Count; }
        }

        public void Clear()
        {
            m_pool.Clear();
        }
    }

服务器端

static void Main(string[] args)
{

    IOCPServer server = new IOCPServer(8088, 1024);
    server.Start();
    Console.WriteLine("服务器已启动....");
    System.Console.ReadLine();
}

客户端

客户端代码也是很简单

static void Main(string[] args)
{
    IPAddress remote = IPAddress.Parse("192.168.3.4");
    client c = new client(8088, remote);

    c.connect();
    Console.WriteLine("服务器连接成功!");
    while (true)
    {
        Console.Write("send>");
        string msg = Console.ReadLine();
        if (msg == "exit")
            break;
        c.send(msg);
    }
    c.disconnect();
    Console.ReadLine();
}

client.cs

public class client
{

    public TcpClient _client;

    public int port;

    public IPAddress remote;

    public client(int port, IPAddress remote)
    {

        this.port = port;
        this.remote = remote;
    }

    public void connect()
    {
        this._client = new TcpClient();
        _client.Connect(remote, port);
    }
    public void disconnect()
    {
        _client.Close();
    }
    public void send(string msg)
    {
        byte[] data = Encoding.Default.GetBytes(msg);
        _client.GetStream().Write(data, 0, data.Length);
    }
}

IOCPClient类，使用SocketAsyncEventArgs类建立一个Socket客户端。

虽然MSDN说这个类特别设计给网络服务器应用，但也没有限制在客户端代码中使用APM。

下面给出了IOCPClient类的样例代码：

public class IOCPClient
{
    /// <summary>
    /// 连接服务器的socket
    /// </summary>
    private Socket _clientSock;

    /// <summary>
    /// 用于服务器执行的互斥同步对象
    /// </summary>
    private static Mutex mutex = new Mutex();
    /// <summary>
    /// Socket连接标志
    /// </summary>
    private Boolean _connected = false;

    private const int ReceiveOperation = 1, SendOperation = 0;

    private static AutoResetEvent[]
    autoSendReceiveEvents = new AutoResetEvent[]
    {
new AutoResetEvent(false),
new AutoResetEvent(false)
    };

    /// <summary>
    /// 服务器监听端点
    /// </summary>
    private IPEndPoint _remoteEndPoint;

    public IOCPClient(IPEndPoint local, IPEndPoint remote)
    {
        _clientSock = new Socket(local.AddressFamily, SocketType.Stream, ProtocolType.Tcp);
        _remoteEndPoint = remote;
    }

    #region 连接服务器

    /// <summary>
    /// 连接远程服务器
    /// </summary>
    public void Connect()
    {
        SocketAsyncEventArgs connectArgs = new SocketAsyncEventArgs();

        connectArgs.UserToken = _clientSock;
        connectArgs.RemoteEndPoint = _remoteEndPoint;
        connectArgs.Completed += new EventHandler<SocketAsyncEventArgs>(OnConnected);
        mutex.WaitOne();
        if (!_clientSock.ConnectAsync(connectArgs))//异步连接
        {
            ProcessConnected(connectArgs);
        }

    }
    /// <summary>
    /// 连接上的事件
    /// </summary>
    /// <param name="sender"></param>
    /// <param name="e"></param>
    void OnConnected(object sender, SocketAsyncEventArgs e)
    {
        mutex.ReleaseMutex();
        //设置Socket已连接标志。 
        _connected = (e.SocketError == SocketError.Success);
    }
    /// <summary>
    /// 处理连接服务器
    /// </summary>
    /// <param name="e"></param>
    private void ProcessConnected(SocketAsyncEventArgs e)
    {
        //TODO
    }

    #endregion

    #region 发送消息
    /// <summary>
    /// 向服务器发送消息
    /// </summary>
    /// <param name="data"></param>
    public void Send(byte[] data)
    {
        SocketAsyncEventArgs asyniar = new SocketAsyncEventArgs();
        asyniar.Completed += new EventHandler<SocketAsyncEventArgs>(OnSendComplete);
        asyniar.SetBuffer(data, 0, data.Length);
        asyniar.UserToken = _clientSock;
        asyniar.RemoteEndPoint = _remoteEndPoint;
        autoSendReceiveEvents[SendOperation].WaitOne();
        if (!_clientSock.SendAsync(asyniar))//投递发送请求，这个函数有可能同步发送出去，这时返回false，并且不会引发SocketAsyncEventArgs.Completed事件
        {
            // 同步发送时处理发送完成事件
            ProcessSend(asyniar);
        }
    }

    /// <summary>
    /// 发送操作的回调方法
    /// </summary>
    /// <param name="sender"></param>
    /// <param name="e"></param>
    private void OnSendComplete(object sender, SocketAsyncEventArgs e)
    {
        //发出发送完成信号。 
        autoSendReceiveEvents[SendOperation].Set();
        ProcessSend(e);
    }

    /// <summary>
    /// 发送完成时处理函数
    /// </summary>
    /// <param name="e">与发送完成操作相关联的SocketAsyncEventArg对象</param>
    private void ProcessSend(SocketAsyncEventArgs e)
    {
        //TODO
    }
    #endregion

    #region 接收消息
    /// <summary>
    /// 开始监听服务端数据
    /// </summary>
    /// <param name="e"></param>
    public void StartRecive(SocketAsyncEventArgs e)
    {
        //准备接收。 
        Socket s = e.UserToken as Socket;
        byte[] receiveBuffer = new byte[255];
        e.SetBuffer(receiveBuffer, 0, receiveBuffer.Length);
        e.Completed += new EventHandler<SocketAsyncEventArgs>(OnReceiveComplete);
        autoSendReceiveEvents[ReceiveOperation].WaitOne();
        if (!s.ReceiveAsync(e))
        {
            ProcessReceive(e);
        }
    }

    /// <summary>
    /// 接收操作的回调方法
    /// </summary>
    /// <param name="sender"></param>
    /// <param name="e"></param>
    private void OnReceiveComplete(object sender, SocketAsyncEventArgs e)
    {
        //发出接收完成信号。 
        autoSendReceiveEvents[ReceiveOperation].Set();
        ProcessReceive(e);
    }

    /// <summary>
    ///接收完成时处理函数
    /// </summary>
    /// <param name="e">与接收完成操作相关联的SocketAsyncEventArg对象</param>
    private void ProcessReceive(SocketAsyncEventArgs e)
    {
        if (e.SocketError == SocketError.Success)
        {
            // 检查远程主机是否关闭连接
            if (e.BytesTransferred > 0)
            {
                Socket s = (Socket)e.UserToken;
                //判断所有需接收的数据是否已经完成
                if (s.Available == 0)
                {
                    byte[] data = new byte[e.BytesTransferred];
                    Array.Copy(e.Buffer, e.Offset, data, 0, data.Length);//从e.Buffer块中复制数据出来，保证它可重用

                    //TODO 处理数据
                }

                if (!s.ReceiveAsync(e))//为接收下一段数据，投递接收请求，这个函数有可能同步完成，这时返回false，并且不会引发SocketAsyncEventArgs.Completed事件
                {
                    //同步接收时处理接收完成事件
                    ProcessReceive(e);
                }
            }
        }
    }

    #endregion


    public void Close()
    {
        _clientSock.Disconnect(false);
    }

    /// <summary>
    /// 失败时关闭Socket，根据SocketError抛出异常。
    /// </summary>
    /// <param name="e"></param>

    private void ProcessError(SocketAsyncEventArgs e)
    {
        Socket s = e.UserToken as Socket;
        if (s.Connected)
        {
            //关闭与客户端关联的Socket
            try
            {
                s.Shutdown(SocketShutdown.Both);
            }
            catch (Exception)
            {
                //如果客户端处理已经关闭，抛出异常 
            }
            finally
            {
                if (s.Connected)
                {
                    s.Close();
                }
            }
        }
        //抛出SocketException 
        throw new SocketException((Int32)e.SocketError);
    }


    /// <summary>
    /// 释放SocketClient实例
    /// </summary>
    public void Dispose()
    {
        mutex.Close();
        autoSendReceiveEvents[SendOperation].Close();
        autoSendReceiveEvents[ReceiveOperation].Close();
        if (_clientSock.Connected)
        {
            _clientSock.Close();
        }
    }

}

 源码下载

源码部分截图如下

1.服务器使用的程序代码，客户端使用的工具测试

 

 

2.服务器和客户端都使用的代码

3.客户端使用的程序代码，服务端使用的工具测试

 

本文引自：https://www.cnblogs.com/tuyile006/p/10980391.html

可供参考：

https://www.iteye.com/blog/freshflower-2285272

https://www.iteye.com/blog/freshflower-2285286