【Socket】苍老师有了丈夫，我也有了SAEA

一、前言

       时间过得真是快，转眼就2018年了。首先祝各位博友，软件开发者新年新气象，事业有成，身体健康，阖家幸福！最近看到园子里好多关于自己的2017年度总结以及对自己新一年的愿景，觉得咱园子的氛围是真的好。这三天假期我也没闲着，一边看OB海鲜团吃鸡一边写Socket SocketAsyncEventArgs 代码。我上一篇博客已经用APM的方式实现了客户端与服务器端的Socket通信，并具有了一定的并发能力。所以这三天我就决定对服务器代码进行改造，使用MS在4.0时发布的SocketAsyncEventArgs（SAEA）写法。为了方便的进行服务器端两种写法的对比，我客户端的代码没有进行变化，依然使用APM方式。代码已经上传至Github，链接会在文末贴出。

二、我的业务功能

       我的业务功能依然是实现从服务器多线程下载更新文件。下载之前的那些操作我基本就不讲了，上一篇博文里的都有，本文还是回到Socket下载文件上。具体流程如下：

在我写SAEA代码之前，我仔细搜了一下网上的资源：MSDN、CNBLOG、CSDN、CodeProject。这四种来源的代码示例的主要流程是这样的：

对比我的流程，您会发现少了一半的通信过程。客户端的代码好写，但是服务器端如何发送完数据之后再接收数据？这中间的衔接过程还是有点门道的。特别是SAEA的代码采用了Buffer池化以及SAEA池化之后，里面有些小的细节就要想清楚了。下面就是具体的代码，我会以我自己的视角去论述APM与SAEA到底有什么区别。

三、对比

     其实对于服务器端的APM，我觉得最重要的并不是代码中的BeginXXX或者是EndXXX，因为这就是APM写法的特征，BeginXXX或者EndXXX然后里面有一个回调函数，在回调函数里去做一些业务上的事情。最重要的是要有一个线程等待的概念，也就是代码中的ManualResetEvent这个东西，它就像地铁闸机一样，处理好一个再放一个进去。APM写法的好处是显而易见的，就是代码看起来十分的简单。缺点依照MS的说法就是如果有过多的客-服交流，可能会产生较多的IAsyncResult对象，这样会增加服务器的开销。  

服务器端的APM写法：

 using System;
 using System.IO;
 using System.Linq;
 using System.Net;
 using System.Net.Sockets;
 using System.Threading;
 using UpdaterShare.GlobalSetting;
 using UpdaterShare.Model;
 using UpdaterShare.Utility;

 namespace UpdaterServerAPM
 {
     public static class ServerSocket
     {
         private static int _downloadChannelsCount;
         private static string _serverPath;
         private static readonly ManualResetEvent AllDone = new ManualResetEvent(false);

         public static void StartServer(int port, int backlog)
         {
             _downloadChannelsCount = DownloadSetting.DownloadChannelsCount;
             try
             {
                 IPAddress ipAddress = IPAddress.Any;
                 IPEndPoint localEndPoint = new IPEndPoint(ipAddress, port);
                 Socket listener = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
                 listener.Bind(localEndPoint);
                 listener.Listen(backlog);

                 while (true)
                 {
                     AllDone.Reset();
                     listener.BeginAccept(AcceptCallback, listener);
                     AllDone.WaitOne();
                 }
             }
             catch (Exception ex)
             {
                 var path = $"{AppDomain.CurrentDomain.BaseDirectory}\\RunLog.txt";
                 File.AppendAllText(path, ex.Message);
             }
         }

         private static void AcceptCallback(IAsyncResult ar)
         {
             AllDone.Set();
             Socket listener = (Socket)ar.AsyncState;
             Socket handler = listener.EndAccept(ar);
             ComObject state = new ComObject { WorkSocket = handler };
             handler.BeginReceive(state.Buffer, , ComObject.BufferSize, , FindUpdateFileCallback, state);
         }

         private static void FindUpdateFileCallback(IAsyncResult ar)
         {
             ComObject state = (ComObject)ar.AsyncState;
             Socket handler = state.WorkSocket;
             int bytesRead = handler.EndReceive(ar);
             if (bytesRead > )
             {
                 var receiveData = state.Buffer.Take(bytesRead).ToArray();
                 var dataList = PacketUtils.SplitBytes(receiveData, PacketUtils.ClientFindFileInfoTag());
                 if (dataList != null && dataList.Any())
                 {
                     var request = PacketUtils.GetData(PacketUtils.ClientFindFileInfoTag(), dataList.FirstOrDefault());
                     string str = System.Text.Encoding.UTF8.GetString(request);
                     var infos = str.Split('_');
                     var productName = infos[];
                     var revitVersion = infos[];
                     var currentVersion = infos[];

                     var mainFolder = AppDomain.CurrentDomain.BaseDirectory.Replace("bin", "TestFile");
                     var serverFileFolder = Path.Combine(mainFolder, "Server");
                     var serverFileFiles = new DirectoryInfo(serverFileFolder).GetFiles();

                     var updatefile  = serverFileFiles.FirstOrDefault(x=>x.Name.Contains(productName) && x.Name.Contains(revitVersion) && x.Name.Contains(currentVersion));
                     if (updatefile != null)
                     {
                         if (string.IsNullOrEmpty(updatefile.FullName) || !File.Exists(updatefile.FullName)) return;
                         _serverPath = updatefile.FullName;
                         FoundUpdateFileResponse(handler);
                     }
                 }
             }
         }

         private static void FoundUpdateFileResponse(Socket handler)
         {
             byte[] foundUpdateFileData = PacketUtils.PacketData(PacketUtils.ServerFoundFileInfoTag(),null);
             ComObject state = new ComObject { WorkSocket = handler };
             handler.BeginSend(foundUpdateFileData, , foundUpdateFileData.Length, , HasFoundUpdateFileCallback, state);
         }

         private static void HasFoundUpdateFileCallback(IAsyncResult ar)
         {
             ComObject state = (ComObject)ar.AsyncState;
             Socket handler = state.WorkSocket;
             handler.EndSend(ar);
             handler.BeginReceive(state.Buffer, , ComObject.BufferSize, , ReadFilePositionRequestCallback, state);
         }

         private static void ReadFilePositionRequestCallback(IAsyncResult ar)
         {
             ComObject state = (ComObject)ar.AsyncState;
             Socket handler = state.WorkSocket;
             int bytesRead = handler.EndReceive(ar);
             if (bytesRead > )
             {
                 var receiveData = state.Buffer.Take(bytesRead).ToArray();
                 var dataList = PacketUtils.SplitBytes(receiveData, PacketUtils.ClientRequestFileTag());
                 if (dataList != null)
                 {
                     foreach (var request in dataList)
                     {
                         if (PacketUtils.IsPacketComplete(request))
                         {
                             int startPosition = PacketUtils.GetRequestFileStartPosition(request);
                             SendFileResponse(handler, startPosition);
                         }
                     }
                 }
             }
         }

         private static void SendFileResponse(Socket handler, int startPosition)
         {
             var packetSize = PacketUtils.GetPacketSize(_serverPath, _downloadChannelsCount);
             if (packetSize != )
             {
                 byte[] filedata = FileUtils.GetFile(_serverPath, startPosition, packetSize);
                 byte[] packetNumber = BitConverter.GetBytes(startPosition/packetSize);
                 if (filedata != null)
                 {
                     byte[] segmentedFileResponseData = PacketUtils.PacketData(PacketUtils.ServerResponseFileTag(), filedata, packetNumber);
                     ComObject state = new ComObject {WorkSocket = handler};
                     handler.BeginSend(segmentedFileResponseData, , segmentedFileResponseData.Length, , SendFileResponseCallback, state);
                 }
             }
             else
             {
                 handler.Shutdown(SocketShutdown.Both);
                 handler.Close();
             }
         }

         private static void SendFileResponseCallback(IAsyncResult ar)
         {
             try
             {
                 ComObject state = (ComObject)ar.AsyncState;
                 Socket handler = state.WorkSocket;
                 handler.EndSend(ar);
                 handler.Shutdown(SocketShutdown.Both);
                 handler.Close();
             }
             catch (Exception e)
             {

             }
         }
     }
 }

说到SAEA，我觉得初入的小伙伴一定要先看MSDN上的实例，特别是它的BufferManager以及SocketAsyncEventArgsPool是怎么写的，到底是干什么用的。这里我可以简单的说下：SocketAsyncEventArgsPool是用来存放SAEA对象的，其个数依赖于你服务器所能承担的队列长度，比如说我服务器能承担100个客户的等待，我就在服务器端生成100个SAEA对象放在池子里，当有客户来连接时，我从池子里取出一个来和他对接。客户走了，我再扔到池子里去。BufferManager则是对池子里的SAEA对象进行Buffer分配的，也相当于一个池子，这个池子的大小是队列长度*通信缓存长度*2，乘以2是因为读与写是分开的。通信缓存长度很好理解，客户端要传个2G的信息给服务器端不可能一下子接收2G，肯定是一口一口吃，那么这一口的大小就是通信缓存长度。那么分配给每个SAEA的缓存是多大呢？当然就是通信缓存长度的大小咯。注意！！注意！！注意！！既然是池化了，所有关于Buffer的操作都要围绕分配给SAEA的Buffer去操作！见148-149行。当服务器拿着分配到的Buffer去接收信息后，如果再要发送信息，所要做的第一件事就是先清空分配的Buffer再使用，BufferManager给你分配哪段你就用哪段，别使用错了。有几个参数需要注意：e.Offset（偏移），e.Count（大小），e.Buffer（缓存字节数组）， e.BytesTransferred（通信传输的字节长度）。如果服务器端要发送数据，一定要用Array.Copy将信息写入对应分配的Buffer中。

说完池化，接着就是写法上的小区别，我觉得区别并不大，无非就是委托换了个写法。当然还要判断下是否为异步操作，如果是否则需要进行同步操作，见82-85行代码。

服务器的SAEA写法：

 using System;
 using System.IO;
 using System.Linq;
 using System.Net;
 using System.Net.Sockets;
 using System.Threading;
 using UpdaterShare.GlobalSetting;
 using UpdaterShare.Model;
 using UpdaterShare.Utility;

 namespace UpdaterServerSAEA
 {
     public class ServerSocket
     {
         private readonly int _port;
         private readonly int _backlog;
         private Socket _listenSocket;
         private const int _opsToPreAlloc = ;
         private readonly BufferManager _bufferManager;
         private readonly SocketAsyncEventArgsPool _readWritePool;
         private readonly Semaphore _maxNumberAcceptedClients;

         private string _serverPath;
         private static readonly int _downloadChannelsCount = DownloadSetting.DownloadChannelsCount;

         public ServerSocket(int port, int backlog)
         {
             _port = port;
             _backlog = backlog;

             _bufferManager = new BufferManager(ComObject.BufferSize * backlog * _opsToPreAlloc, ComObject.BufferSize);
             _readWritePool = new SocketAsyncEventArgsPool(backlog);
             _maxNumberAcceptedClients = new Semaphore(backlog, backlog);
         }

         private void Init()
         {
             _bufferManager.InitBuffer();

             for (var i = ; i < _backlog; i++)
             {
                 var readWriteEventArg = new SocketAsyncEventArgs();
                 _bufferManager.SetBuffer(readWriteEventArg);
                 _readWritePool.Push(readWriteEventArg);
             }
         }

         public void StartServer()
         {
             try
             {
                 Init();
                 IPAddress ipAddress = IPAddress.Any;
                 IPEndPoint localEndPoint = new IPEndPoint(ipAddress, _port);
                 _listenSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
                 _listenSocket.Bind(localEndPoint);
                 _listenSocket.Listen(_backlog);
                 StartAccept(null);
             }
             catch (Exception ex)
             {
                 Console.WriteLine(ex.Message);
             }
         }

         private void StartAccept(SocketAsyncEventArgs acceptEventArg)
         {
             if (acceptEventArg == null)
             {
                 acceptEventArg = new SocketAsyncEventArgs();
                 acceptEventArg.Completed += StartAccept_Completed;
             }
             else
             {
                 acceptEventArg.AcceptSocket = null;
             }

             _maxNumberAcceptedClients.WaitOne();

             if (!_listenSocket.AcceptAsync(acceptEventArg))
             {
                 ProcessAccept(acceptEventArg);
             }
         }

         private void StartAccept_Completed(object sender, SocketAsyncEventArgs e)
         {
             ProcessAccept(e);
         }

         private void ProcessAccept(SocketAsyncEventArgs e)
         {
             if (e.SocketError == SocketError.Success)
             {
                 var socket = e.AcceptSocket;
                 if (socket.Connected)
                 {
                     SocketAsyncEventArgs readEventArgs = _readWritePool.Pop();
                     readEventArgs.AcceptSocket = socket;
                     readEventArgs.Completed += ProcessAccept_Completed;
                     if (!socket.ReceiveAsync(readEventArgs))
                     {
                         ProcessReceiveFindFileRequest(readEventArgs);
                     }
                     StartAccept(e);
                 }
             }
         }

         private void ProcessAccept_Completed(object sender, SocketAsyncEventArgs e)
         {
             ProcessReceiveFindFileRequest(e);
         }

         private void ProcessReceiveFindFileRequest(SocketAsyncEventArgs e)
         {
             var bytesRead = e.BytesTransferred;
             if (bytesRead >  && e.SocketError == SocketError.Success)
             {
                 var receiveData = e.Buffer.Skip(e.Offset).Take(bytesRead).ToArray();
                 var dataList = PacketUtils.SplitBytes(receiveData, PacketUtils.ClientFindFileInfoTag());
                 if (dataList != null && dataList.Any())
                 {
                     var request = PacketUtils.GetData(PacketUtils.ClientFindFileInfoTag(), dataList.FirstOrDefault());
                     string str = System.Text.Encoding.UTF8.GetString(request);
                     var infos = str.Split('_');
                     var productName = infos[];
                     var revitVersion = infos[];
                     var currentVersion = infos[];

                     var mainFolder = AppDomain.CurrentDomain.BaseDirectory.Replace("bin", "TestFile");
                     var serverFileFolder = Path.Combine(mainFolder, "Server");
                     var serverFileFiles = new DirectoryInfo(serverFileFolder).GetFiles();

                     var updatefile = serverFileFiles.FirstOrDefault(x => x.Name.Contains(productName) && x.Name.Contains(revitVersion) && x.Name.Contains(currentVersion));
                     if (updatefile != null)
                     {
                         if (string.IsNullOrEmpty(updatefile.FullName) || !File.Exists(updatefile.FullName)) return;
                         _serverPath = updatefile.FullName;

                         //ready to send back to Client
                         byte[] foundUpdateFileData = PacketUtils.PacketData(PacketUtils.ServerFoundFileInfoTag(), null);

                         Array.Clear(e.Buffer, e.Offset, e.Count);
                         Array.Copy(foundUpdateFileData, , e.Buffer, e.Offset, foundUpdateFileData.Length);

                         e.Completed -= ProcessAccept_Completed;
                         e.Completed += ProcessReceiveFindFileRequest_Completed;

                         if (!e.AcceptSocket.SendAsync(e))
                         {
                             ProcessFilePosition(e);
                         }
                     }
                 }
             }
         }

         private void ProcessReceiveFindFileRequest_Completed(object sender, SocketAsyncEventArgs e)
         {
             ProcessFilePosition(e);
         }

         private void ProcessFilePosition(SocketAsyncEventArgs e)
         {
             if (e.SocketError == SocketError.Success)
             {
                 var socket = e.AcceptSocket;
                 if (socket.Connected)
                 {
                     //clear buffer
                     Array.Clear(e.Buffer, e.Offset, e.Count);

                     e.Completed -= ProcessReceiveFindFileRequest_Completed;
                     e.Completed += ProcessFilePosition_Completed;

                     if (!socket.ReceiveAsync(e))
                     {
                         ProcessSendFile(e);
                     }
                 }
             }
         }

         private void ProcessFilePosition_Completed(object sender, SocketAsyncEventArgs e)
         {
             ProcessSendFile(e);
         }

         private void ProcessSendFile(SocketAsyncEventArgs e)
         {
             var bytesRead = e.BytesTransferred;
             if (bytesRead >  && e.SocketError == SocketError.Success)
             {
                 var receiveData = e.Buffer.Skip(e.Offset).Take(bytesRead).ToArray();
                 var dataList = PacketUtils.SplitBytes(receiveData, PacketUtils.ClientRequestFileTag());
                 if (dataList != null)
                 {
                     foreach (var request in dataList)
                     {
                         if (PacketUtils.IsPacketComplete(request))
                         {
                             int startPosition = PacketUtils.GetRequestFileStartPosition(request);

                             var packetSize = PacketUtils.GetPacketSize(_serverPath, _downloadChannelsCount);
                             if (packetSize != )
                             {
                                 byte[] filedata = FileUtils.GetFile(_serverPath, startPosition, packetSize);
                                 byte[] packetNumber = BitConverter.GetBytes(startPosition / packetSize);

                                 Console.WriteLine("Receive File Request PacketNumber: "+startPosition / packetSize);

                                 if (filedata != null)
                                 {
                                     //ready to send back to Client
                                     byte[] segmentedFileResponseData = PacketUtils.PacketData(PacketUtils.ServerResponseFileTag(), filedata, packetNumber);

                                     Array.Clear(e.Buffer, e.Offset, e.Count);
                                     Array.Copy(segmentedFileResponseData, , e.Buffer, e.Offset, segmentedFileResponseData.Length);

                                     e.Completed -= ProcessFilePosition_Completed;
                                     e.Completed += ProcessSendFile_Completed;

                                     if (!e.AcceptSocket.SendAsync(e))
                                     {
                                         CloseClientSocket(e);
                                     }
                                 }
                             }
                         }
                     }
                 }
             }
             else
             {
                 CloseClientSocket(e);
             }
         }

         private void ProcessSendFile_Completed(object sender, SocketAsyncEventArgs e)
         {
             CloseClientSocket(e);
         }

         private void CloseClientSocket(SocketAsyncEventArgs e)
         {
             try
             {
                 e.AcceptSocket.Shutdown(SocketShutdown.Both);
                 e.AcceptSocket.Close();
             }
             catch (Exception ex)
             {
                 Console.WriteLine(ex.Message);
             }
             finally
             {
                 _maxNumberAcceptedClients.Release();
                 _readWritePool.Push(e);
             }
         }
     }
 }

四、总结

      坑坑洼洼总算是写完了SAEA的代码，由于本人知识面有限，如果说的不对，还请各位及时直接提出批评与建议，我这个人比较在乎技术不在乎面子的。

附：

MSDN示例：

https://msdn.microsoft.com/en-us/library/system.net.sockets.socketasynceventargs(v=vs.110).aspx

启蒙博客：

http://www.cnblogs.com/gaochundong/p/csharp_tcp_service_models.html

大神改造：

http://freshflower.iteye.com/blog/2285272

架构狂魔：

http://www.cnblogs.com/jiahuafu/archive/2013/01/05/2845631.html

我的GitHub

https://github.com/airforce094/Socket_APM-SAEA