networkComms.net2.3.1开源版本，基于gpl V3协议。因为不能公开3.x版本的源码，所以基于此版本进行学习。3.X版本进行了诸多改进和Bug修复，使用方法上两者相差不大。

namespace NetworkCommsDotNet{    /// <summary>    /// Connection对象  这个类是TcpConnection和 UDPConnnection连接类的父类    /// Connection由以下五个文件组成 大家注意到每个类前面都有个 partial关键字    /// ConnectionCreate.cs <1>    /// ConnectionDelegatesHandlers.cs <2>    /// ConnectionIncomingData.cs <3>    /// ConnectionSendClose.cs <4>    /// ConnectionStatic.cs  <5>    /// </summary>       public abstract partial class Connection    {        static ManualResetEvent workedThreadSignal = new ManualResetEvent(false);        static volatile bool shutdownWorkerThreads = false;        static object staticConnectionLocker = new object();        static Thread connectionKeepAliveWorker;        /// <summary>        /// 一些默认的设置        /// </summary>        static Connection()        {            ConnectionKeepAlivePollIntervalSecs = 30;            MaxNumSendTimes = 100;            MinNumSendsBeforeConnectionSpecificSendTimeout = 4;            MinSendTimeoutMS = 2000;            MinimumMSPerKBSendTimeout = 20;            DefaultMSPerKBSendTimeout = 1000;            NumberOfStDeviationsForWriteTimeout = 3;        }        /// <summary>        /// 每KB数据发送超时的最小时间 默认为10.        /// </summary>        public static double MinimumMSPerKBSendTimeout { get; set; }        /// <summary>        /// 写入间隔的最大时间  默认100        /// </summary>        public static int MaxNumSendTimes { get; set; }        /// <summary>        /// The minimum number of writes before the connection specific write timeouts will be used. Default is 3.        /// </summary>        public static int MinNumSendsBeforeConnectionSpecificSendTimeout { get; set; }        /// <summary>        /// The default milliseconds per KB write timeout before connection specific values become available. Default is 1000. See <see cref="MinNumSendsBeforeConnectionSpecificSendTimeout"/>.        /// </summary>        public static int DefaultMSPerKBSendTimeout { get; set; }        /// <summary>        /// The minimum timeout for any sized send in milliseconds. Prevents timeouts when sending less than 1KB. Default is 500.        /// </summary>        public static int MinSendTimeoutMS { get; set; }        /// <summary>        /// The interval between keep alive polls of all connections. Set to int.MaxValue to disable keep alive poll        /// </summary>        public static int ConnectionKeepAlivePollIntervalSecs { get; set; }        /// <summary>        /// The number of standard deviations from the mean to use for write timeouts. Default is 4.0.        /// </summary>        public static double NumberOfStDeviationsForWriteTimeout { get; set; }               /// 如果 connectionKeepAliveWorker线程没有启动，则启动之 这个线程主要用来进行心跳检测              protected static void TriggerConnectionKeepAliveThread()        {            lock (staticConnectionLocker)            {                if (!shutdownWorkerThreads && (connectionKeepAliveWorker == null || connectionKeepAliveWorker.ThreadState == ThreadState.Stopped))                {                    connectionKeepAliveWorker = new Thread(ConnectionKeepAliveWorker);                    connectionKeepAliveWorker.Name = "ConnectionKeepAliveWorker";                    connectionKeepAliveWorker.Start();                }            }        }              /// 一个单独的静态工作者线程，用来保持连接是活动的              private static void ConnectionKeepAliveWorker()        {            if (NetworkComms.LoggingEnabled) NetworkComms.Logger.Debug("Connection keep alive polling thread has started.");            DateTime lastPollCheck = DateTime.Now;            while (!shutdownWorkerThreads)            {                try                {                    //We have a short sleep here so that we can exit the thread fairly quickly if we need too                    if (ConnectionKeepAlivePollIntervalSecs == int.MaxValue)                        workedThreadSignal.WaitOne(5000);                    else                        workedThreadSignal.WaitOne(100);                    //Check for shutdown here                    if (shutdownWorkerThreads) break;                    //Any connections which we have not seen in the last poll interval get tested using a null packet                    if (ConnectionKeepAlivePollIntervalSecs < int.MaxValue && (DateTime.Now - lastPollCheck).TotalSeconds > (double)ConnectionKeepAlivePollIntervalSecs)                    {                        AllConnectionsSendNullPacketKeepAlive();                        lastPollCheck = DateTime.Now;                    }                }                catch (Exception ex)                {                    NetworkComms.LogError(ex, "ConnectionKeepAlivePollError");                }            }        }        /// <summary>        /// Polls all existing connections based on ConnectionKeepAlivePollIntervalSecs value. Serverside connections are polled slightly earlier than client side to help reduce potential congestion.        /// </summary>        /// <param name="returnImmediately"></param>        private static void AllConnectionsSendNullPacketKeepAlive(bool returnImmediately = false)        {            if (NetworkComms.LoggingEnabled) NetworkComms.Logger.Trace("Starting AllConnectionsSendNullPacketKeepAlive");            //Loop through all connections and test the alive state            List<Connection> allConnections = NetworkComms.GetExistingConnection();            int remainingConnectionCount = allConnections.Count;#if WINDOWS_PHONE            QueueItemPriority nullSendPriority = QueueItemPriority.High;#else            QueueItemPriority nullSendPriority = QueueItemPriority.AboveNormal;#endif            ManualResetEvent allConnectionsComplete = new ManualResetEvent(false);            for (int i = 0; i < allConnections.Count; i++)            {                //We don‘t send null packets to unconnected udp connections                UDPConnection asUDP = allConnections[i] as UDPConnection;                if (asUDP != null && asUDP.UDPOptions == UDPOptions.None)                {                    if (Interlocked.Decrement(ref remainingConnectionCount) == 0)                        allConnectionsComplete.Set();                    continue;                }                else                {                    int innerIndex = i;                    NetworkComms.CommsThreadPool.EnqueueItem(nullSendPriority, new WaitCallback((obj) =>                    {                        try                        {                            //If the connection is server side we poll preferentially                            if (allConnections[innerIndex] != null)                            {                                if (allConnections[innerIndex].ConnectionInfo.ServerSide)                                {                                    //We check the last incoming traffic time                                    //In scenarios where the client is sending us lots of data there is no need to poll                                    if ((DateTime.Now - allConnections[innerIndex].ConnectionInfo.LastTrafficTime).TotalSeconds > ConnectionKeepAlivePollIntervalSecs)                                        allConnections[innerIndex].SendNullPacket();                                }                                else                                {                                    //If we are client side we wait upto an additional 3 seconds to do the poll                                    //This means the server will probably beat us                                    if ((DateTime.Now - allConnections[innerIndex].ConnectionInfo.LastTrafficTime).TotalSeconds > ConnectionKeepAlivePollIntervalSecs + 1.0 + (NetworkComms.randomGen.NextDouble() * 2.0))                                        allConnections[innerIndex].SendNullPacket();                                }                            }                        }                        catch (Exception) { }                        finally                        {                            if (Interlocked.Decrement(ref remainingConnectionCount) == 0)                                allConnectionsComplete.Set();                        }                    }), null);                }            }            //Max wait is 1 seconds per connection            if (!returnImmediately && allConnections.Count > 0)            {                if (!allConnectionsComplete.WaitOne(allConnections.Count * 2500))                    //This timeout should not really happen so we are going to log an error if it does                    NetworkComms.LogError(new TimeoutException("Timeout after " + allConnections.Count.ToString() + " seconds waiting for null packet sends to finish. " + remainingConnectionCount.ToString() + " connection waits remain. This error indicates very high send load or a possible send deadlock."), "NullPacketKeepAliveTimeoutError");            }        }        /// <summary>        /// Shutdown any static connection components        /// </summary>        /// <param name="threadShutdownTimeoutMS"></param>        internal static void ShutdownBase(int threadShutdownTimeoutMS = 1000)        {            try            {                shutdownWorkerThreads = true;                if (connectionKeepAliveWorker != null && !connectionKeepAliveWorker.Join(threadShutdownTimeoutMS))                    connectionKeepAliveWorker.Abort();            }            catch (Exception ex)            {                NetworkComms.LogError(ex, "CommsShutdownError");            }            finally            {                shutdownWorkerThreads = false;                workedThreadSignal.Reset();            }        }    }}