Socket连接池

　　“池”这个概念好像最早是在操作系统的课上听过的，到后来出来工作的第二天组长也跟我提起“池”这个东东。它给我的感觉是某种对象的集合，如果要用的话就取出，不用的话就放回。在学多线程的时候有接触过线程池，在写《Socket 一对多通信》的时候想到了Socket连接池这回事，不过在网上谷歌了一下，发现这类的文章貌似不多，看了一下园友的博文《高性能Socket设计实现》，获益良多，下了份源码来看，虽然有一部分看不明白，而且由于个人水平跑不了那份代码，但是从中我学到了不少，至少我写的“池”有一部分是用了这位田大哥的思想。

　　先来分析各个类之间的结构，整个连接池里面实际上是有两个池，一个是在异步通信中可以重复利用的SocketAsyncEventArgs池(当然处于别的方面考虑，池里面并不是单纯放SocketAsyncEventArgs的实例集合)，另一个是接收数据时用到的byte[]缓冲池。而这两个池是外部不能访问的，外部通过一个控制(或者叫管理)的类进行操作。继承了前两篇博文中的异步通信的思想，最底的一个类存放了一次连接的信息，包括两个SocketAsyncEventArgs实例和通信另一端的Socket实例。下面将逐部分介绍。

    /// <summary>
    /// 连接单元
    /// </summary>
     class ConnectionUnit:IDisposable
    {
        private string _uid;//单元的编号，默认为-1
        private bool _state;//单元的状态，true表示使用，false表示空闲
        private SocketAsyncEventArgs _sendArg;//专用于发送
        private SocketAsyncEventArgs _recArg;//专用于接收
        internal Socket client { get; set; }//客户端的socket实例
        internal ArrayList tempArray { get; set; }//暂存已接收的数据，避免粘包用的


        public ConnectionUnit(string UID)
        {
            _uid = UID;
            tempArray = new ArrayList();
        }

        public ConnectionUnit() : this("-1") { }

        public void Dispose()
        {
            if (_sendArg != null)
                _sendArg.Dispose();
            if (_recArg != null)
                _recArg.Dispose();

            _sendArg = null;
            _recArg = null;
        }
    }

　　这个与之前一篇讲异步通信的博文一样，一个Socket两个SocketAsyncEventArgs。为了取客户端的Socket方便一点，两个SocketAsyncEventArgs一个用于收，一个用于发，田大哥说这样可以实现双工。的确是这样，当初把类定成这样也是为了在收的同时也能发。以上代码删掉了把字段装成属性的那部分。

　　SocketAsyncEventArgsPool这个类就是上面链接单元的一个池，这个池才是整个连接池里最核心的池，也是真正意义上的池。池里面用了两个集合来存放这一堆连接单元。分别是空闲栈(freeCollecton)和在线字典集(busyCollection)。对于这样的一个池，我就认为，只要在我需要用的时候把对象取出来，顶多在去的时候给一些参数，让池帮忙把这个对象配置好，我就拿来使用，等到我用完了，把他放回池里，池就把对象还原，等待下次再使用。正体感觉这个池对外有点像个栈，取的时候就Pop，放的时候就Push，此外还提供了两个与栈不相干的的方法，根据编号获取在线的连接单元和获取所有在线连接单元的编号。

    class SocketAsyncEventArgsPool:IDisposable
    {
        private Dictionary<string, ConnectionUnit> busyCollection;
        private Stack<ConnectionUnit> freeCollecton;

        internal SocketAsyncEventArgsPool()
        {
            busyCollection = new Dictionary<string, ConnectionUnit>();
            freeCollecton = new Stack<ConnectionUnit>();
        }

        /// <summary>
        /// 取出
        /// </summary>
        internal ConnectionUnit Pop(string uid)
        {
            ConnectionUnit unit = freeCollecton.Pop();
            unit.State = true;
            unit.Uid = uid;
            busyCollection.Add(uid, unit);
            return unit;
        }

        /// <summary>
        /// 放回
        /// </summary>
        internal void Push(ConnectionUnit unit)
        {
            if (!string.IsNullOrEmpty(unit.Uid) && unit.Uid != "-1")
                busyCollection.Remove(unit.Uid);
            unit.Uid = "-1";
            unit.State = false;
            freeCollecton.Push(unit);
        }

        /// <summary>
        /// 获取
        /// </summary>
        internal ConnectionUnit GetConnectionUnitByUID(string uid)
        {
            if (busyCollection.ContainsKey(uid))
                return busyCollection[uid];
            return null;
        }

        /// <summary>
        /// 
        /// </summary>
        internal string[] GetOnLineList()
        {
            return busyCollection.Keys.ToArray();
        }

        public void Dispose()
        {
            foreach (KeyValuePair<string,ConnectionUnit> item in busyCollection)
                item.Value.Dispose();

            busyCollection.Clear();

            while (freeCollecton.Count > 0)
                freeCollecton.Pop().Dispose();
        }

　　BufferManager这个是专给接收的SocketAsyncEventArgs用的缓冲池，整一个连接池里面所有接收用的缓冲区都用这个BufferManager，参照田大哥的思想，现在内存里开辟一大片区域存放byte，然后给每一个接收用的SocketAsyncEventArgs分配一块。

    class BufferManager:IDisposable
    {
        private byte[] buffers;//缓冲池
        private int bufferSize;//每个单元使用的大小
        private int allSize;//池的总大小
        private int currentIndex;//当前可用的索引
        private Stack<int> freeIndexs;//已使用过的空闲索引

        /// <summary>
        /// 构造缓存池
        /// </summary>
        /// <param name="buffersSize">池总大小</param>
        /// <param name="defaultSize">默认单元大小</param>
        internal BufferManager(int buffersSize, int defaultSize) 
        {
            this.bufferSize=defaultSize;
            this.allSize=buffersSize;
            currentIndex=0;
            this.buffers = new byte[allSize];
            freeIndexs = new Stack<int>();
        }

        /// <summary>
        /// 给SocketAsyncEventArgs设置缓冲区
        /// </summary>
        internal bool SetBuffer(SocketAsyncEventArgs e)
        {
            //首先看看空闲栈里有没有空闲的区域，有就使用
            if (freeIndexs.Count > 0)
            {
                e.SetBuffer(buffers, freeIndexs.Pop(), bufferSize);
            }
            else
            {
                //没有就得从buffers里取，如果buffers用光了当然取不了
                if ((allSize - currentIndex) < bufferSize) return false;
                e.SetBuffer(buffers, currentIndex, bufferSize);
                currentIndex += bufferSize;
            }
            return true;
        }

        /// <summary>
        /// 释放SocketAsyncEventArgs的缓冲区
        /// </summary>
        /// <param name="e"></param>
        internal void FreeBuffer(SocketAsyncEventArgs e)
        {
            //把索引放到空闲索引栈里面，供下次取的时候重复利用
            freeIndexs.Push(e.Offset);
            //同时清空这部分区域的数据免得上次使用时遗留的数据会掺
            //和到下次读取的数据中
            for (int i = e.Offset; i < e.Offset + bufferSize; i++)
            {
                if (buffers[i] == 0) break;
                buffers[i] = 0;
            }
            e.SetBuffer(null, 0, 0);
        }

        public void Dispose()
        {
            buffers = null;
            freeIndexs = null;
        }
    }

　　其实上面两个池都是很大程度参照了《高性能Socket设计实现》中的内容。下面这个SocketPoolController是对外的类，这个类的设计参照的就没那么多了。而对于一个Socket通信(服务端的)来说，无非都是三件事，接受连接，接收数据，发送数据。这三件事我再操作类里面是这样做的

　　接受连接：接受再运行池的时候就开始了，异步循环地接受，执行一次异步接受就阻塞，等到接受完成才被唤醒。

        /// <summary>
        /// 异步Accept客户端的连接
        /// </summary>
        void MyAsyncAccept()
        {
            //这里使用Action的方式异步循环接受客户端的连接
            //模仿同事的做法没开线程，不知这种方式是好是坏
            Action callback = new Action(delegate()
            {
                while (true)
                {
                    //每次接受都要新开一个SocketAsyncEventArgs,否则会报错
                    //其实我也想重复利用的
                    SocketAsyncEventArgs e = new SocketAsyncEventArgs();
                    e.Completed += new EventHandler<SocketAsyncEventArgs>(Accept_Completed);
                    
                    acceptLock.Reset();
                    server.AcceptAsync(e);
                    //在异步接受完成之前阻塞当前线程
                    acceptLock.WaitOne();
                }
            });
            callback.BeginInvoke(null, null);
        }

        void Accept_Completed(object sender, SocketAsyncEventArgs e)
        {
            Socket client = e.AcceptSocket;
            try
            {
                if (client.Connected)
                {
                    IPEndPoint point = client.RemoteEndPoint as IPEndPoint;
                    string uid = point.Address + ":" + point.Port;
                    ConnectionUnit unit = pool.Pop(uid);
                    unit.client = client;
                    unit.State = true;
                    unit.Uid = uid;
                    unit.RecArg.UserToken = unit;
                    unit.SendArg.UserToken = unit;
                    buffer.SetBuffer(unit.RecArg);

                    //在接受成功之后就开始接收数据了
                    client.ReceiveAsync(unit.RecArg);
                    //设置并发限制信号和增加当前连接数
                    semaphoreAccept.WaitOne();
                    Interlocked.Increment(ref currentConnect);

                    if (OnAccept != null) OnAccept(uid);
                }
                else if (client != null)
                {
                    client.Close();
                    client.Dispose();
                    client = null;
                }
            }
            catch (Exception ex) { Console.WriteLine(ex.ToString()); }
            //设置Accept信号，以便下次Accept的执行
            acceptLock.Set();
            e.Dispose();
        }

　　接收消息：在异步接受成功的时候开始接收，每次接收完成之后就进行下一次接收，直到客户端断开连接才终止。

        void RecArg_Completed(object sender, SocketAsyncEventArgs e)
        {
            Socket client = sender as Socket;
            ConnectionUnit unit = e.UserToken as ConnectionUnit;
            //这里大致与上一篇异步通信的一样，只是对缓冲区的处理有一点差异
            if (e.SocketError == SocketError.Success)
            {
                int rec = e.BytesTransferred;
                if (rec == 0)
                {
                    CloseSocket(unit);
                    return;
                }
                if (client.Available > 0)
                {
                    unit.tempArray.AddRange(e.Buffer);
                    buffer.FreeBuffer(unit.RecArg);
                    buffer.SetBuffer(unit.RecArg);
                    client.SendAsync(unit.RecArg);
                    return;
                }
                byte[] data = e.Buffer;
                int len = rec;
                int offset = e.Offset;
                if (unit.tempArray.Count != 0)
                {
                    foreach (byte item in data)
                    {
                        if (item == 0) break;
                        unit.tempArray.Add(item);
                    }
                    data = unit.tempArray.ToArray(typeof(byte)) as byte[];
                    rec = data.Length;
                    offset = 0;
                    unit.tempArray.Clear();
                }

                string dataStr = Encoding.ASCII.GetString(data,offset,len);
                if (OnReceive != null)
                    OnReceive(unit.Uid, dataStr);

                if (!unit.State) return;
                buffer.FreeBuffer(e);
                buffer.SetBuffer(e);
                client.ReceiveAsync(e);
            }
            //这里还多个了一个关闭当前连接
            else
            {
                CloseSocket(unit);
            }
        }

        /// <summary>
        /// 关闭一个连接单元
        /// </summary>
        private void CloseSocket( ConnectionUnit unit )
        {
            //关闭并释放客户端socket的字眼
            if (unit.client != null)
            {
                unit.client.Shutdown(SocketShutdown.Both);
                unit.client.Dispose();
                unit.client = null;
            }
            //Console.WriteLine(unit.Uid+" disconnect ");
            //把连接放回连接池
            pool.Push(unit);
            //释放并发信号
            semaphoreAccept.Release();
            //减少当前连接数
            Interlocked.Decrement(ref currentConnect);
        }

　　发送消息：外放方法，在需要的时候自行调用方法发送。

        /// <summary>
        /// 发送消息
        /// </summary>
        /// <param name="uid"></param>
        /// <param name="message"></param>
        public void SendMessage(string uid, string message)
        {
            sendLock.Reset();
            ConnectionUnit unit=pool.GetConnectionUnitByUID(uid);
            //如果获取不了连接单元就不发送了，
            if (unit == null)
            { 
                if(OnSend!=null) OnSend(uid,"100");
                sendLock.Set();
                return;
            }
            byte[] datas = Encoding.ASCII.GetBytes(message);
            unit.SendArg.SetBuffer(datas, 0, datas.Length);
            unit.client.SendAsync(unit.SendArg);
            //阻塞当前线程，等到发送完成才释放
            sendLock.WaitOne();
        }

        void SendArg_Completed(object sender, SocketAsyncEventArgs e)
        {
            Socket client = sender as Socket;
            ConnectionUnit unit = e.UserToken as ConnectionUnit;
            //这里的消息码有三个，2字头的是成功的，1字头是不成功的
            //101是未知错误，100是客户端不在线
            if (e.SocketError == SocketError.Success)
                if (OnSend != null) OnSend(unit.Uid, "200");
            else if (OnSend != null) OnSend(unit.Uid, "101");
            //释放信号，以便下次发送消息执行
            sendLock.Set();
        }

　　下面则是类里面的一些字段信息和构造函数

        /// <summary>
        /// 初始化池的互斥体
        /// </summary>
        private Mutex mutex = new Mutex();

        /// <summary>
        /// Accept限制信号
        /// </summary>
        private Semaphore semaphoreAccept;

        /// <summary>
        /// Accept信号
        /// </summary>
        private static ManualResetEvent acceptLock = new ManualResetEvent(false);

        /// <summary>
        /// Send信号
        /// </summary>
        private static ManualResetEvent sendLock = new ManualResetEvent(false);

        /// <summary>
        /// 最大并发数(连接数)
        /// </summary>
        private int maxConnect;

        /// <summary>
        /// 当前连接数(并发数)
        /// </summary>
        private int currentConnect;

        /// <summary>
        /// 缓冲池
        /// </summary>
        private BufferManager buffer;

        /// <summary>
        /// SocketasyncEventArgs池
        /// </summary>
        private SocketAsyncEventArgsPool pool;

        /// <summary>
        /// 服务端Socket
        /// </summary>
        private Socket server;

        /// <summary>
        /// 完成接受的委托
        /// </summary>
        public delegate void AcceptHandler(string uid);

        /// <summary>
        /// 完成发送的委托
        /// </summary>
        public delegate void SendHandler(string uid, string result);

        /// <summary>
        /// 完成接收的委托
        /// </summary>
        public delegate void RecevieHandler(string uid, string data);

        /// <summary>
        /// 完成接受事件
        /// </summary>
        public event AcceptHandler OnAccept;

        /// <summary>
        /// 完成发送事件
        /// </summary>
        public event SendHandler OnSend;

        /// <summary>
        /// 完成接收事件
        /// </summary>
        public event RecevieHandler OnReceive;

        /// <summary>
        /// 构造函数
        /// </summary>
        /// <param name="buffersize">单元缓冲区大小</param>
        /// <param name="maxCount">并发总数</param>
        public SocketPoolController(int buffersize, int maxCount)
        {
            buffer = new BufferManager(buffersize * maxCount,buffersize);
            this.currentConnect = 0;
            this.maxConnect = maxCount;
            this.currentConnect = 0;
            this.pool = new SocketAsyncEventArgsPool();
            //设置并发数信号，经试验过是并发数-1才对
            this.semaphoreAccept = new Semaphore(maxCount-1, maxCount-1);
            InitPool();
        }

构造函数里用到的方法

        /// <summary>
        /// 初始化SocketAsyncEventArgs池
        /// 这里主要是给空闲栈填充足够的实例
        /// </summary>
        private void InitPool()
        {
            ConnectionUnit unit = null;
            for (int i = 0; i < maxConnect; i++)
            {
                unit = new ConnectionUnit();
                unit.Uid = "-1";
                unit.RecArg = new SocketAsyncEventArgs();
                unit.RecArg.Completed += new EventHandler<SocketAsyncEventArgs>(RecArg_Completed);
                unit.SendArg = new SocketAsyncEventArgs();
                unit.SendArg.Completed += new EventHandler<SocketAsyncEventArgs>(SendArg_Completed);
                this.pool.Push(unit);
            }
        }

　　其他外放专门控制池的方法

        /// <summary>
        /// 启动池
        /// </summary>
        /// <param name="ipAddress">服务端的IP</param>
        /// <param name="port">端口</param>
        public void RunPool(string ipAddress, int port)
        {
            IPEndPoint endpoint = new IPEndPoint(IPAddress.Parse(ipAddress), port);
            server = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
            server.Bind(endpoint);
            server.Listen(100);

            //调用方法异步Accept客户端的连接
            MyAsyncAccept();
            //设置信号，防止再池在已经启动的情况下再次启动
            mutex.WaitOne();
        }

        /// <summary>
        /// 停止池
        /// </summary>
        public void StopPool()
        {
            //把服务端的socket关了
            if (server != null)
                server.Close();
            //释放互斥信号，等待下次启动
            mutex.ReleaseMutex();
            //释放资源
            Dispose();
        }

　　要把这个操作类与现实的事物类比的话，这个与我们平常跟某个或一堆人聊天时差不多，别人说的东西，不用你自己控制你都会听得到(排除带上耳机，塞住耳朵这种极端的情况)，所以接收消息那个方法就不需要了，而你要说什么这个要靠个人控制，而事件那些也好类比，OnAccept就相当于某人加入到这次聊天中你会做些什么(say hello 或者无视)，OnRecevie就听到别人说什么自己有什么反应，OnSend就自己说完话之后有什么反应(有时候发现说错了会纠正，有时觉得自己说得好笑的也笑一场诸如此类)。

　　在使用的时候可以这样子

            SocketPoolController pool;
            pool = new SocketPoolController(32 * 1024, 1000);
            pool.OnReceive += new SocketPoolController.RecevieHandler(pool_OnReceive);
            pool.OnSend += new SocketPoolController.SendHandler(pool_OnSend);
            pool.OnAccept += new SocketPoolController.AcceptHandler(pool_OnAccept);
            pool.RunPool("127.0.0.1", 8081);
            Console.WriteLine("Pool has run\r\npress any key to stop...");
            Console.ReadKey();
            pool.StopPool();
            Console.WriteLine("Pool has stop\r\npress any key to exit...");
            Console.ReadLine();

　　在池里面有一部分地方看似跟用同步的差不多，像接受客户端的连接，发送消息这些地方。可是用这种异步，万一客户端突然断开连接也不会有同步那样马上抛异常。还有一点的是在这份代码里面缺少了对异常的捕捉，有一部分错误我在测试的过程中设了判断避开了。以前跟某只猫提过Socket编程会与多线程一起使用，我也觉得是这样，在之前一篇博文 《Socket一对多通信》里我也用到线程，后来的异步通信也是有线程的，不过不是.net framework自行创建的。看了田大哥的博文给我的另一个收获是信号量的使用，在以前不懂得使用信号量，只会设置一大堆标识状态的布尔值或整形的变量来计数判断。田大哥的博文介绍的时高性能的Socket，而我的这个应该性能不会高到哪里去。上面有什么说错的请各位指出，有什么说漏的，请各位提点，多多指导。谢谢！

    /// <summary>
    /// 连接单元
    /// </summary>
    class ConnectionUnit:IDisposable
    {
        private string _uid;//单元的编号，默认为-1
        private bool _state;//单元的状态，true表示使用，false表示空闲
        private SocketAsyncEventArgs _sendArg;//专用于发送
        private SocketAsyncEventArgs _recArg;//专用于接收
        internal Socket client { get; set; }//客户端的socket实例
        internal ArrayList tempArray { get; set; }//暂存已接收的数据，避免粘包用的

        public string Uid
        {
            get { return _uid; }
            set { _uid = value; }
        }

        public ConnectionUnit(string UID)
        {
            _uid = UID;
            tempArray = new ArrayList();
        }

        public ConnectionUnit() : this("-1") { }

        public bool State
        {
            get { return _state; }
            set { _state = value; }
        }

        public SocketAsyncEventArgs SendArg
        {
            get { return _sendArg; }
            set { _sendArg = value; }
        }

        public SocketAsyncEventArgs RecArg
        {
            get { return _recArg; }
            set { _recArg = value; }
        }

        public void Dispose()
        {
            if (_sendArg != null)
                _sendArg.Dispose();
            if (_recArg != null)
                _recArg.Dispose();

            _sendArg = null;
            _recArg = null;
        }
    }

    class BufferManager:IDisposable
    {
        private byte[] buffers;
        private int bufferSize;
        private int allSize;
        private int currentIndex;
        private Stack<int> freeIndexs;

        /// <summary>
        /// 构造缓存池
        /// </summary>
        /// <param name="buffersSize">池总大小</param>
        /// <param name="defaultSize">默认单元大小</param>
        internal BufferManager(int buffersSize, int defaultSize) 
        {
            this.bufferSize=defaultSize;
            this.allSize=buffersSize;
            currentIndex=0;
            this.buffers = new byte[allSize];
            freeIndexs = new Stack<int>();
        }

        /// <summary>
        /// 
        /// </summary>
        /// <param name="e"></param>
        /// <param name="offSet"></param>
        /// <returns></returns>
        internal bool SetBuffer(SocketAsyncEventArgs e)
        {
            if (freeIndexs.Count > 0)
            {
                e.SetBuffer(buffers, freeIndexs.Pop(), bufferSize);
            }
            else
            {
                if ((allSize - currentIndex) < bufferSize) return false;
                e.SetBuffer(buffers, currentIndex, bufferSize);
                currentIndex += bufferSize;
            }
            return true;
        }

        /// <summary>
        /// 
        /// </summary>
        /// <param name="e"></param>
        internal void FreeBuffer(SocketAsyncEventArgs e)
        {
            freeIndexs.Push(e.Offset);
            for (int i = e.Offset; i < e.Offset + bufferSize; i++)
            {
                if (buffers[i] == 0) break;
                buffers[i] = 0;
            }
            e.SetBuffer(null, 0, 0);
        }

        public void Dispose()
        {
            buffers = null;
            freeIndexs = null;
        }
    }

    class SocketAsyncEventArgsPool:IDisposable
    {
        private Dictionary<string, ConnectionUnit> busyCollection;
        private Stack<ConnectionUnit> freeCollecton;

        internal SocketAsyncEventArgsPool()
        {
            busyCollection = new Dictionary<string, ConnectionUnit>();
            freeCollecton = new Stack<ConnectionUnit>();
        }

        /// <summary>
        /// 取出
        /// </summary>
        internal ConnectionUnit Pop(string uid)
        {
            ConnectionUnit unit = freeCollecton.Pop();
            unit.State = true;
            unit.Uid = uid;
            busyCollection.Add(uid, unit);
            return unit;
        }

        /// <summary>
        /// 放回
        /// </summary>
        internal void Push(ConnectionUnit unit)
        {
            if (!string.IsNullOrEmpty(unit.Uid) && unit.Uid != "-1")
                busyCollection.Remove(unit.Uid);
            unit.Uid = "-1";
            unit.State = false;
            freeCollecton.Push(unit);
        }

        /// <summary>
        /// 获取
        /// </summary>
        internal ConnectionUnit GetConnectionUnitByUID(string uid)
        {
            if (busyCollection.ContainsKey(uid))
                return busyCollection[uid];
            return null;
        }

        /// <summary>
        /// 
        /// </summary>
        internal string[] GetOnLineList()
        {
            return busyCollection.Keys.ToArray();
        }

        public void Dispose()
        {
            foreach (KeyValuePair<string,ConnectionUnit> item in busyCollection)
                item.Value.Dispose();

            busyCollection.Clear();

            while (freeCollecton.Count > 0)
                freeCollecton.Pop().Dispose();
        }
    }

    public class SocketPoolController:IDisposable
    {
        /// <summary>
        /// 初始化池的互斥体
        /// </summary>
        private Mutex mutex = new Mutex();

        /// <summary>
        /// Accept限制信号
        /// </summary>
        private Semaphore semaphoreAccept;

        /// <summary>
        /// Accept信号
        /// </summary>
        private static ManualResetEvent acceptLock = new ManualResetEvent(false);

        /// <summary>
        /// Send信号
        /// </summary>
        private static ManualResetEvent sendLock = new ManualResetEvent(false);

        /// <summary>
        /// 最大并发数(连接数)
        /// </summary>
        private int maxConnect;

        /// <summary>
        /// 当前连接数(并发数)
        /// </summary>
        private int currentConnect;

        /// <summary>
        /// 缓冲池
        /// </summary>
        private BufferManager buffer;

        /// <summary>
        /// SocketasyncEventArgs池
        /// </summary>
        private SocketAsyncEventArgsPool pool;

        /// <summary>
        /// 服务端Socket
        /// </summary>
        private Socket server;

        /// <summary>
        /// 完成接受的委托
        /// </summary>
        public delegate void AcceptHandler(string uid);

        /// <summary>
        /// 完成发送的委托
        /// </summary>
        public delegate void SendHandler(string uid, string result);

        /// <summary>
        /// 完成接收的委托
        /// </summary>
        public delegate void RecevieHandler(string uid, string data);

        /// <summary>
        /// 完成接受事件
        /// </summary>
        public event AcceptHandler OnAccept;

        /// <summary>
        /// 完成发送事件
        /// </summary>
        public event SendHandler OnSend;

        /// <summary>
        /// 完成接收事件
        /// </summary>
        public event RecevieHandler OnReceive;

        /// <summary>
        /// 构造函数
        /// </summary>
        /// <param name="buffersize">单元缓冲区大小</param>
        /// <param name="maxCount">并发总数</param>
        public SocketPoolController(int buffersize, int maxCount)
        {
            buffer = new BufferManager(buffersize * maxCount,buffersize);
            this.currentConnect = 0;
            this.maxConnect = maxCount;
            this.currentConnect = 0;
            this.pool = new SocketAsyncEventArgsPool();
            //设置并发数信号，经试验过是并发数-1才对
            this.semaphoreAccept = new Semaphore(maxCount-1, maxCount-1);
            InitPool();
        }

        /// <summary>
        /// 初始化SocketAsyncEventArgs池
        /// 这里主要是给空闲栈填充足够的实例
        /// </summary>
        private void InitPool()
        {
            ConnectionUnit unit = null;
            for (int i = 0; i < maxConnect; i++)
            {
                unit = new ConnectionUnit();
                unit.Uid = "-1";
                unit.RecArg = new SocketAsyncEventArgs();
                unit.RecArg.Completed += new EventHandler<SocketAsyncEventArgs>(RecArg_Completed);
                unit.SendArg = new SocketAsyncEventArgs();
                unit.SendArg.Completed += new EventHandler<SocketAsyncEventArgs>(SendArg_Completed);
                this.pool.Push(unit);
            }
        }

        /// <summary>
        /// 启动池
        /// </summary>
        /// <param name="ipAddress">服务端的IP</param>
        /// <param name="port">端口</param>
        public void RunPool(string ipAddress, int port)
        {
            IPEndPoint endpoint = new IPEndPoint(IPAddress.Parse(ipAddress), port);
            server = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
            server.Bind(endpoint);
            server.Listen(100);

            //调用方法异步Accept客户端的连接
            MyAsyncAccept();
            //设置信号，防止再池在已经启动的情况下再次启动
            mutex.WaitOne();
        }

        /// <summary>
        /// 异步Accept客户端的连接
        /// </summary>
        void MyAsyncAccept()
        {
            //这里使用Action的方式异步循环接受客户端的连接
            //模仿同事的做法没开线程，不知这种方式是好是坏
            Action callback = new Action(delegate()
            {
                while (true)
                {
                    //每次接受都要新开一个SocketAsyncEventArgs,否则会报错
                    //其实我也想重复利用的
                    SocketAsyncEventArgs e = new SocketAsyncEventArgs();
                    e.Completed += new EventHandler<SocketAsyncEventArgs>(Accept_Completed);
                    
                    acceptLock.Reset();
                    server.AcceptAsync(e);
                    //在异步接受完成之前阻塞当前线程
                    acceptLock.WaitOne();
                }
            });
            callback.BeginInvoke(null, null);
        }


        /// <summary>
        /// 停止池
        /// </summary>
        public void StopPool()
        {
            //把服务端的socket关了
            if (server != null)
                server.Close();
            //释放互斥信号，等待下次启动
            mutex.ReleaseMutex();
            //释放资源
            Dispose();
        }

        /// <summary>
        /// 发送消息
        /// </summary>
        /// <param name="uid"></param>
        /// <param name="message"></param>
        public void SendMessage(string uid, string message)
        {
            sendLock.Reset();
            ConnectionUnit unit=pool.GetConnectionUnitByUID(uid);
            //如果获取不了连接单元就不发送了，
            if (unit == null)
            { 
                if(OnSend!=null) OnSend(uid,"100");
                sendLock.Set();
                return;
            }
            byte[] datas = Encoding.ASCII.GetBytes(message);
            unit.SendArg.SetBuffer(datas, 0, datas.Length);
            unit.client.SendAsync(unit.SendArg);
            //阻塞当前线程，等到发送完成才释放
            sendLock.WaitOne();
        }

        void SendArg_Completed(object sender, SocketAsyncEventArgs e)
        {
            Socket client = sender as Socket;
            ConnectionUnit unit = e.UserToken as ConnectionUnit;
            //这里的消息码有三个，2字头的是成功的，1字头是不成功的
            //101是未知错误，100是客户端不在线
            if (e.SocketError == SocketError.Success)
                if (OnSend != null) OnSend(unit.Uid, "200");
            else if (OnSend != null) OnSend(unit.Uid, "101");
            //释放信号，以便下次发送消息执行
            sendLock.Set();
        }

        void RecArg_Completed(object sender, SocketAsyncEventArgs e)
        {
            Socket client = sender as Socket;
            ConnectionUnit unit = e.UserToken as ConnectionUnit;
            //这里大致与上一篇异步通信的一样，只是对缓冲区的处理有一点差异
            if (e.SocketError == SocketError.Success)
            {
                int rec = e.BytesTransferred;
                if (rec == 0)
                {
                    CloseSocket(unit);
                    return;
                }
                if (client.Available > 0)
                {
                    unit.tempArray.AddRange(e.Buffer);
                    buffer.FreeBuffer(unit.RecArg);
                    buffer.SetBuffer(unit.RecArg);
                    client.SendAsync(unit.RecArg);
                    return;
                }
                byte[] data = e.Buffer;
                int len = rec;
                if (unit.tempArray.Count != 0)
                {
                    foreach (byte item in data)
                    {
                        if (item == 0) break;
                        unit.tempArray.Add(item);
                    }
                    data = unit.tempArray.ToArray(typeof(byte)) as byte[];
                    rec = data.Length;
                    unit.tempArray.Clear();
                }

                string dataStr = Encoding.ASCII.GetString(data, 0, len);
                if (OnReceive != null)
                    OnReceive(unit.Uid, dataStr);

                if (!unit.State) return;
                buffer.FreeBuffer(e);
                buffer.SetBuffer(e);
                client.ReceiveAsync(e);
            }
            //这里还多个了一个关闭当前连接
            else
            {
                CloseSocket(unit);
            }
        }

        void Accept_Completed(object sender, SocketAsyncEventArgs e)
        {
            Socket client = e.AcceptSocket;
            try
            {
                if (client.Connected)
                {
                    IPEndPoint point = client.RemoteEndPoint as IPEndPoint;
                    string uid = point.Address + ":" + point.Port;
                    ConnectionUnit unit = pool.Pop(uid);
                    unit.client = client;
                    unit.State = true;
                    unit.Uid = uid;
                    unit.RecArg.UserToken = unit;
                    unit.SendArg.UserToken = unit;
                    buffer.SetBuffer(unit.RecArg);

                    //在接受成功之后就开始接收数据了
                    client.ReceiveAsync(unit.RecArg);
                    //设置并发限制信号和增加当前连接数
                    semaphoreAccept.WaitOne();
                    Interlocked.Increment(ref currentConnect);

                    if (OnAccept != null) OnAccept(uid);
                }
                else if (client != null)
                {
                    client.Close();
                    client.Dispose();
                    client = null;
                }
            }
            catch (Exception ex) { Console.WriteLine(ex.ToString()); }
            //设置Accept信号，以便下次Accept的执行
            acceptLock.Set();
            e.Dispose();
        }

        /// <summary>
        /// 关闭一个连接单元
        /// </summary>
        private void CloseSocket( ConnectionUnit unit )
        {
            //关闭并释放客户端socket的字眼
            if (unit.client != null)
            {
                unit.client.Shutdown(SocketShutdown.Both);
                unit.client.Dispose();
                unit.client = null;
            }
            //Console.WriteLine(unit.Uid+" disconnect ");
            //把连接放回连接池
            pool.Push(unit);
            //释放并发信号
            semaphoreAccept.Release();
            //减少当前连接数
            Interlocked.Decrement(ref currentConnect);
        }
        
        public void Dispose()
        {
            if (pool != null)
            {
                pool.Dispose();
                pool = null;
            }
            if (buffer != null)
            {
                buffer.Dispose();
                buffer = null;
            }
            if (server != null)
            {
                server.Dispose();
                server = null;
            }

        }
    }