C#高性能大容量SOCKET并发（二）：SocketAsyncEventArgs封装

原文:C#高性能大容量SOCKET并发（二）：SocketAsyncEventArgs封装

1、SocketAsyncEventArgs介绍

SocketAsyncEventArgs是微软提供的高性能异步Socket实现类，主要为高性能网络服务器应用程序而设计，主要是为了避免在在异步套接字 I/O 量非常大时发生重复的对象分配和同步。使用此类执行异步套接字操作的模式包含以下步骤：

1.分配一个新的 SocketAsyncEventArgs 上下文对象，或者从应用程序池中获取一个空闲的此类对象。

2.将该上下文对象的属性设置为要执行的操作（例如，完成回调方法、数据缓冲区、缓冲区偏移量以及要传输的最大数据量）。

3.调用适当的套接字方法 (xxxAsync) 以启动异步操作。

4.如果异步套接字方法 (xxxAsync) 返回 true，则在回调中查询上下文属性来获取完成状态。

5.如果异步套接字方法 (xxxAsync) 返回 false，则说明操作是同步完成的。可以查询上下文属性来获取操作结果。

6.将该上下文重用于另一个操作，将它放回到应用程序池中，或者将它丢弃。

2、SocketAsyncEventArgs封装

使用SocketAsyncEventArgs之前需要先建立一个Socket监听对象，使用如下代码：

        public void Start(IPEndPoint localEndPoint)

        {

            listenSocket = new Socket(localEndPoint.AddressFamily, SocketType.Stream, ProtocolType.Tcp);

            listenSocket.Bind(localEndPoint);

            listenSocket.Listen(m_numConnections);

            Program.Logger.InfoFormat("Start listen socket {0} success", localEndPoint.ToString());

            //for (int i = 0; i < 64; i++) //不能循环投递多次AcceptAsync，会造成只接收8000连接后不接收连接了

            StartAccept(null);

            m_daemonThread = new DaemonThread(this);

        }

然后开始接受连接，SocketAsyncEventArgs有连接时会通过Completed事件通知外面，所以接受连接的代码如下：

        public void StartAccept(SocketAsyncEventArgs acceptEventArgs)

        {

            if (acceptEventArgs == null)

            {

                acceptEventArgs = new SocketAsyncEventArgs();

                acceptEventArgs.Completed += new EventHandler<SocketAsyncEventArgs>(AcceptEventArg_Completed);

            }

            else

            {

                acceptEventArgs.AcceptSocket = null; //释放上次绑定的Socket，等待下一个Socket连接

            }

            m_maxNumberAcceptedClients.WaitOne(); //获取信号量

            bool willRaiseEvent = listenSocket.AcceptAsync(acceptEventArgs);

            if (!willRaiseEvent)

            {

                ProcessAccept(acceptEventArgs);

            }

        }

接受连接响应事件代码：

        void AcceptEventArg_Completed(object sender, SocketAsyncEventArgs acceptEventArgs)

        {

            try

            {

                ProcessAccept(acceptEventArgs);

            }

            catch (Exception E)

            {

                Program.Logger.ErrorFormat("Accept client {0} error, message: {1}", acceptEventArgs.AcceptSocket, E.Message);

                Program.Logger.Error(E.StackTrace);

            }

        }

        private void ProcessAccept(SocketAsyncEventArgs acceptEventArgs)

        {

            Program.Logger.InfoFormat("Client connection accepted. Local Address: {0}, Remote Address: {1}",

                acceptEventArgs.AcceptSocket.LocalEndPoint, acceptEventArgs.AcceptSocket.RemoteEndPoint);

            AsyncSocketUserToken userToken = m_asyncSocketUserTokenPool.Pop();

            m_asyncSocketUserTokenList.Add(userToken); //添加到正在连接列表

            userToken.ConnectSocket = acceptEventArgs.AcceptSocket;

            userToken.ConnectDateTime = DateTime.Now;

            try

            {

                bool willRaiseEvent = userToken.ConnectSocket.ReceiveAsync(userToken.ReceiveEventArgs); //投递接收请求

                if (!willRaiseEvent)

                {

                    lock (userToken)

                    {

                        ProcessReceive(userToken.ReceiveEventArgs);

                    }

                }

            }

            catch (Exception E)

            {

                Program.Logger.ErrorFormat("Accept client {0} error, message: {1}", userToken.ConnectSocket, E.Message);

                Program.Logger.Error(E.StackTrace);

            }            

            StartAccept(acceptEventArgs); //把当前异步事件释放，等待下次连接

        }

接受连接后，从当前Socket缓冲池AsyncSocketUserTokenPool中获取一个用户对象AsyncSocketUserToken，AsyncSocketUserToken包含一个接收异步事件m_receiveEventArgs，一个发送异步事件m_sendEventArgs，接收数据缓冲区m_receiveBuffer，发送数据缓冲区m_sendBuffer，协议逻辑调用对象m_asyncSocketInvokeElement，建立服务对象后，需要实现接收和发送的事件响应函数：

        void IO_Completed(object sender, SocketAsyncEventArgs asyncEventArgs)

        {

            AsyncSocketUserToken userToken = asyncEventArgs.UserToken as AsyncSocketUserToken;

            userToken.ActiveDateTime = DateTime.Now;

            try

            {

                lock (userToken)

                {

                    if (asyncEventArgs.LastOperation == SocketAsyncOperation.Receive)

                        ProcessReceive(asyncEventArgs);

                    else if (asyncEventArgs.LastOperation == SocketAsyncOperation.Send)

                        ProcessSend(asyncEventArgs);

                    else

                        throw new ArgumentException("The last operation completed on the socket was not a receive or send");

                }

            }

            catch (Exception E)

            {

                Program.Logger.ErrorFormat("IO_Completed {0} error, message: {1}", userToken.ConnectSocket, E.Message);

                Program.Logger.Error(E.StackTrace);

            }

        }

在Completed事件中需要处理发送和接收的具体逻辑代码，其中接收的逻辑实现如下：

        private void ProcessReceive(SocketAsyncEventArgs receiveEventArgs)

        {

            AsyncSocketUserToken userToken = receiveEventArgs.UserToken as AsyncSocketUserToken;

            if (userToken.ConnectSocket == null)

                return;

            userToken.ActiveDateTime = DateTime.Now;

            if (userToken.ReceiveEventArgs.BytesTransferred > 0 && userToken.ReceiveEventArgs.SocketError == SocketError.Success)

            {

                int offset = userToken.ReceiveEventArgs.Offset;

                int count = userToken.ReceiveEventArgs.BytesTransferred;

                if ((userToken.AsyncSocketInvokeElement == null) & (userToken.ConnectSocket != null)) //存在Socket对象，并且没有绑定协议对象，则进行协议对象绑定

                {

                    BuildingSocketInvokeElement(userToken);

                    offset = offset + 1;

                    count = count - 1;

                }

                if (userToken.AsyncSocketInvokeElement == null) //如果没有解析对象，提示非法连接并关闭连接

                {

                    Program.Logger.WarnFormat("Illegal client connection. Local Address: {0}, Remote Address: {1}", userToken.ConnectSocket.LocalEndPoint,

                        userToken.ConnectSocket.RemoteEndPoint);

                    CloseClientSocket(userToken);

                }

                else

                {

                    if (count > 0) //处理接收数据

                    {

                        if (!userToken.AsyncSocketInvokeElement.ProcessReceive(userToken.ReceiveEventArgs.Buffer, offset, count))

                        { //如果处理数据返回失败，则断开连接

                            CloseClientSocket(userToken);

                        }

                        else //否则投递下次介绍数据请求

                        {

                            bool willRaiseEvent = userToken.ConnectSocket.ReceiveAsync(userToken.ReceiveEventArgs); //投递接收请求

                            if (!willRaiseEvent)

                                ProcessReceive(userToken.ReceiveEventArgs);

                        }

                    }

                    else

                    {

                        bool willRaiseEvent = userToken.ConnectSocket.ReceiveAsync(userToken.ReceiveEventArgs); //投递接收请求

                        if (!willRaiseEvent)

                            ProcessReceive(userToken.ReceiveEventArgs);

                    }

                }

            }

            else

            {

                CloseClientSocket(userToken);

            }

        }

由于我们制定的协议第一个字节是协议标识，因此在接收到第一个字节的时候需要绑定协议解析对象，具体代码实现如下：

        private void BuildingSocketInvokeElement(AsyncSocketUserToken userToken)

        {

            byte flag = userToken.ReceiveEventArgs.Buffer[userToken.ReceiveEventArgs.Offset];

            if (flag == (byte)SocketFlag.Upload)

                userToken.AsyncSocketInvokeElement = new UploadSocketProtocol(this, userToken);

            else if (flag == (byte)SocketFlag.Download)

                userToken.AsyncSocketInvokeElement = new DownloadSocketProtocol(this, userToken);

            else if (flag == (byte)SocketFlag.RemoteStream)

                userToken.AsyncSocketInvokeElement = new RemoteStreamSocketProtocol(this, userToken);

            else if (flag == (byte)SocketFlag.Throughput)

                userToken.AsyncSocketInvokeElement = new ThroughputSocketProtocol(this, userToken);

            else if (flag == (byte)SocketFlag.Control)

                userToken.AsyncSocketInvokeElement = new ControlSocketProtocol(this, userToken);

            else if (flag == (byte)SocketFlag.LogOutput)

                userToken.AsyncSocketInvokeElement = new LogOutputSocketProtocol(this, userToken);

            if (userToken.AsyncSocketInvokeElement != null)

            {

                Program.Logger.InfoFormat("Building socket invoke element {0}.Local Address: {1}, Remote Address: {2}",

                    userToken.AsyncSocketInvokeElement, userToken.ConnectSocket.LocalEndPoint, userToken.ConnectSocket.RemoteEndPoint);

            }

        }

发送响应函数实现需要注意，我们是把发送数据放到一个列表中，当上一个发送事件完成响应Completed事件，这时我们需要检测发送队列中是否存在未发送的数据，如果存在则继续发送。

        private bool ProcessSend(SocketAsyncEventArgs sendEventArgs)

        {

            AsyncSocketUserToken userToken = sendEventArgs.UserToken as AsyncSocketUserToken;

            if (userToken.AsyncSocketInvokeElement == null)

                return false;

            userToken.ActiveDateTime = DateTime.Now;

            if (sendEventArgs.SocketError == SocketError.Success)

                return userToken.AsyncSocketInvokeElement.SendCompleted(); //调用子类回调函数

            else

            {

                CloseClientSocket(userToken);

                return false;

            }

        }

SendCompleted用于回调下次需要发送的数据，具体实现过程如下：

        public virtual bool SendCompleted()

        {

            m_activeDT = DateTime.UtcNow;

            m_sendAsync = false;

            AsyncSendBufferManager asyncSendBufferManager = m_asyncSocketUserToken.SendBuffer;

            asyncSendBufferManager.ClearFirstPacket(); //清除已发送的包

            int offset = 0;

            int count = 0;

            if (asyncSendBufferManager.GetFirstPacket(ref offset, ref count))

            {

                m_sendAsync = true;

                return m_asyncSocketServer.SendAsyncEvent(m_asyncSocketUserToken.ConnectSocket, m_asyncSocketUserToken.SendEventArgs,

                    asyncSendBufferManager.DynamicBufferManager.Buffer, offset, count);

            }

            else

                return SendCallback();

        }

        //发送回调函数，用于连续下发数据

        public virtual bool SendCallback()

        {

            return true;

        }

当一个SocketAsyncEventArgs断开后，我们需要断开对应的Socket连接，并释放对应资源，具体实现函数如下：

        public void CloseClientSocket(AsyncSocketUserToken userToken)

        {

            if (userToken.ConnectSocket == null)

                return;

            string socketInfo = string.Format("Local Address: {0} Remote Address: {1}", userToken.ConnectSocket.LocalEndPoint,

                userToken.ConnectSocket.RemoteEndPoint);

            Program.Logger.InfoFormat("Client connection disconnected. {0}", socketInfo);

            try

            {

                userToken.ConnectSocket.Shutdown(SocketShutdown.Both);

            }

            catch (Exception E)

            {

                Program.Logger.ErrorFormat("CloseClientSocket Disconnect client {0} error, message: {1}", socketInfo, E.Message);

            }

            userToken.ConnectSocket.Close();

            userToken.ConnectSocket = null; //释放引用，并清理缓存，包括释放协议对象等资源

            m_maxNumberAcceptedClients.Release();

            m_asyncSocketUserTokenPool.Push(userToken);

            m_asyncSocketUserTokenList.Remove(userToken);

        }

3、SocketAsyncEventArgs封装和MSDN的不同点

MSDN在http://msdn.microsoft.com/zh-cn/library/system.net.sockets.socketasynceventargs(v=vs.110).aspx实现了示例代码，并实现了初步的池化处理，我们是在它的基础上扩展实现了接收数据缓冲，发送数据队列，并把发送SocketAsyncEventArgs和接收SocketAsyncEventArgs分开，并实现了协议解析单元，这样做的好处是方便后续逻辑实现文件的上传，下载和日志输出。

DEMO下载地址：http://download.csdn.net/detail/sqldebug_fan/7467745

免责声明：此代码只是为了演示C#完成端口编程，仅用于学习和研究，切勿用于商业用途。水平有限，C#也属于初学，错误在所难免，欢迎指正和指导。邮箱地址：fansheng_hx@163.com。

巴特西

C#高性能大容量SOCKET并发（二）：SocketAsyncEventArgs封装

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