protected void IncomingPacketHandleHandOff(PacketBuilder packetBuilder)        {            try            {                if (NetworkComms.LoggingEnabled) NetworkComms.Logger.Trace(" ... checking for completed packet with " + packetBuilder.TotalBytesCached.ToString() + " bytes read.");                if (packetBuilder.TotalPartialPacketCount == 0)                    throw new Exception("Executing IncomingPacketHandleHandOff when no packets exist in packetbuilder.");                //循环，直到我们完成对packetBuilder的处理                //Loop until we are finished with this packetBuilder                int loopCounter = 0;                while (true)                {                    //If we have ended up with a null packet at the front, probably due to some form of concatentation we can pull it off here                    //It is possible we have concatenation of several null packets along with real data so we loop until the firstByte is greater than 0                    //此处，可能是处理心跳检测时对方发来的0字节数据                    if (packetBuilder.FirstByte() == 0)                    {                        if (NetworkComms.LoggingEnabled) NetworkComms.Logger.Trace(" ... null packet removed in IncomingPacketHandleHandOff() from " + ConnectionInfo + ", loop index - " + loopCounter.ToString());                        packetBuilder.ClearNTopBytes(1);                        //Reset the expected bytes to 0 so that the next check starts from scratch                        packetBuilder.TotalBytesExpected = 0;                        //If we have run out of data completely then we can return immediately                        if (packetBuilder.TotalBytesCached == 0) return;                    }                    else                    {                        //First determine the expected size of a header packet                        //获取数据包包头长度                        int packetHeaderSize = packetBuilder.FirstByte() + 1;                        //Do we have enough data to build a header?                        //如果没有足够的二级制数据来还原出一个数据包包头                        if (packetBuilder.TotalBytesCached < packetHeaderSize)                        {                            if (NetworkComms.LoggingEnabled) NetworkComms.Logger.Trace(" ... ... more data required for complete packet header.");                            //Set the expected number of bytes and then return                            packetBuilder.TotalBytesExpected = packetHeaderSize;                            return;                        }                        //We have enough for a header                        //有足够的数据来还原出数据包包头                        PacketHeader topPacketHeader;                        using(MemoryStream headerStream = packetBuilder.ReadDataSection(1, packetHeaderSize - 1))                            //数据包包头                            topPacketHeader = new PacketHeader(headerStream, NetworkComms.InternalFixedSendReceiveOptions);                        //Idiot test                        if (topPacketHeader.PacketType == null)                            throw new SerialisationException("packetType value in packetHeader should never be null");                        //We can now use the header to establish if we have enough payload data                        //First case is when we have not yet received enough data                         //如果没有足够的数据来还原出数据包                        if (packetBuilder.TotalBytesCached < packetHeaderSize + topPacketHeader.PayloadPacketSize)                        {                            if (NetworkComms.LoggingEnabled) NetworkComms.Logger.Trace(" ... ... more data required for complete packet payload. Expecting " + (packetHeaderSize + topPacketHeader.PayloadPacketSize).ToString() + " total packet bytes.");                            //Set the expected number of bytes and then return                            packetBuilder.TotalBytesExpected = packetHeaderSize + topPacketHeader.PayloadPacketSize;                            return;                        }                        //Second case is we have enough data                        //有足够的数据还原出数据包                        else if (packetBuilder.TotalBytesCached >= packetHeaderSize + topPacketHeader.PayloadPacketSize)                        {                            //We can either have exactly the right amount or even more than we were expecting                            //We may have too much data if we are sending high quantities and the packets have been concatenated                            //no problem!!                            SendReceiveOptions incomingPacketSendReceiveOptions = IncomingPacketSendReceiveOptions(topPacketHeader);                            if (NetworkComms.LoggingEnabled) NetworkComms.Logger.Debug("Received packet of type '" + topPacketHeader.PacketType + "' from " + ConnectionInfo + ", containing " + packetHeaderSize.ToString() + " header bytes and " + topPacketHeader.PayloadPacketSize.ToString() + " payload bytes.");                            //If this is a reserved packetType we call the method inline so that it gets dealt with immediately                            //判断是否为保留类型，保留类型会优先处理                            //保留类型包括心跳检测、连接建立等                            bool isReservedType = false;                            foreach (var tName in NetworkComms.reservedPacketTypeNames)                            {                                //isReservedType |= topPacketHeader.PacketType == tName;                                if (topPacketHeader.PacketType == tName)                                {                                    isReservedType = true;                                    break;                                }                            }                            //Only reserved packet types get completed inline                            //如果数据包类型为保留类型  设定为高优先级                            if (isReservedType)                            {#if WINDOWS_PHONE                                var priority = QueueItemPriority.Normal;#else                                var priority = (QueueItemPriority)Thread.CurrentThread.Priority;#endif                                //创建优先级队列项目                                PriorityQueueItem item = new PriorityQueueItem(priority, this, topPacketHeader, packetBuilder.ReadDataSection(packetHeaderSize, topPacketHeader.PayloadPacketSize), incomingPacketSendReceiveOptions);                                if (NetworkComms.LoggingEnabled) NetworkComms.Logger.Trace(" ... handling packet type '" + topPacketHeader.PacketType + "' inline. Loop index - " + loopCounter.ToString());                                NetworkComms.CompleteIncomingItemTask(item);                            }                            else                            {                                //创建优先级队列项目                                QueueItemPriority itemPriority = (incomingPacketSendReceiveOptions.Options.ContainsKey("ReceiveHandlePriority") ? (QueueItemPriority)Enum.Parse(typeof(QueueItemPriority), incomingPacketSendReceiveOptions.Options["ReceiveHandlePriority"]) : QueueItemPriority.Normal);                                //把数据包包头，和数据包数据 赋值给优先级队列项                                  PriorityQueueItem item = new PriorityQueueItem(itemPriority, this, topPacketHeader, packetBuilder.ReadDataSection(packetHeaderSize, topPacketHeader.PayloadPacketSize), incomingPacketSendReceiveOptions);                                //QueueItemPriority.Highest is the only priority that is executed inline#if !WINDOWS_PHONE                                //如果是最高优先级，当前线程处理                                if (itemPriority == QueueItemPriority.Highest)                                {                                    if (NetworkComms.LoggingEnabled) NetworkComms.Logger.Trace(" ... handling packet type '" + topPacketHeader.PacketType + "' with priority HIGHEST inline. Loop index - " + loopCounter.ToString());                                    NetworkComms.CompleteIncomingItemTask(item);                                }                                else                                {                                    //不是最高优先级 交给自定义线程池处理   此线程池支持优先级处理                                    int threadId = NetworkComms.CommsThreadPool.EnqueueItem(item.Priority, NetworkComms.CompleteIncomingItemTask, item);                                    if (NetworkComms.LoggingEnabled) NetworkComms.Logger.Trace(" ... added completed " + item.PacketHeader.PacketType + " packet to thread pool (Q:" + NetworkComms.CommsThreadPool.QueueCount.ToString() + ", T:" + NetworkComms.CommsThreadPool.CurrentNumTotalThreads.ToString() + ", I:" + NetworkComms.CommsThreadPool.CurrentNumIdleThreads.ToString() + ") with priority " + itemPriority.ToString() + (threadId > 0 ? ". Selected threadId=" + threadId.ToString() : "") + ". Loop index=" + loopCounter.ToString() + ".");                                }#else                                int threadId = NetworkComms.CommsThreadPool.EnqueueItem(item.Priority, NetworkComms.CompleteIncomingItemTask, item);                                if (NetworkComms.LoggingEnabled) NetworkComms.Logger.Trace(" ... added completed " + item.PacketHeader.PacketType + " packet to thread pool (Q:" + NetworkComms.CommsThreadPool.QueueCount.ToString() + ", T:" + NetworkComms.CommsThreadPool.CurrentNumTotalThreads.ToString() + ", I:" + NetworkComms.CommsThreadPool.CurrentNumIdleThreads.ToString() + ") with priority " + itemPriority.ToString() + (threadId > 0 ? ". Selected threadId=" + threadId.ToString() : "") + ". Loop index=" + loopCounter.ToString() + ".");#endif                            }                            //从PacketBuilder中删除已经处理过的数据                            //We clear the bytes we have just handed off                            if (NetworkComms.LoggingEnabled) NetworkComms.Logger.Trace("Removing " + (packetHeaderSize + topPacketHeader.PayloadPacketSize).ToString() + " bytes from incoming packet buffer from connection with " + ConnectionInfo +".");                            packetBuilder.ClearNTopBytes(packetHeaderSize + topPacketHeader.PayloadPacketSize);                            //Reset the expected bytes to 0 so that the next check starts from scratch                            packetBuilder.TotalBytesExpected = 0;                            //If we have run out of data completely then we can return immediately                            if (packetBuilder.TotalBytesCached == 0) return;                        }                        else                            throw new CommunicationException("This should be impossible!");                    }                    loopCounter++;                }            }            catch (Exception ex)            {                //Any error, throw an exception.                if (NetworkComms.LoggingEnabled) NetworkComms.Logger.Fatal("A fatal exception occured in IncomingPacketHandleHandOff(), connection with " + ConnectionInfo + " be closed. See log file for more information.");                NetworkComms.LogError(ex, "CommsError");                CloseConnection(true, 45);            }        }