【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：

  1 using System;
  2 using System.IO;
  3 using System.Linq;
  4 using System.Net;
  5 using System.Net.Sockets;
  6 using System.Threading;
  7 using UpdaterShare.GlobalSetting;
  8 using UpdaterShare.Model;
  9 using UpdaterShare.Utility;
 10 
 11 namespace UpdaterServerAPM
 12 {  
 13     public static class ServerSocket
 14     {
 15         private static int _downloadChannelsCount;
 16         private static string _serverPath;
 17         private static readonly ManualResetEvent AllDone = new ManualResetEvent(false);
 18 
 19         public static void StartServer(int port, int backlog)
 20         {         
 21             _downloadChannelsCount = DownloadSetting.DownloadChannelsCount;
 22             try
 23             {
 24                 IPAddress ipAddress = IPAddress.Any;
 25                 IPEndPoint localEndPoint = new IPEndPoint(ipAddress, port);
 26                 Socket listener = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
 27                 listener.Bind(localEndPoint);
 28                 listener.Listen(backlog);
 29 
 30                 while (true)
 31                 {
 32                     AllDone.Reset();
 33                     listener.BeginAccept(AcceptCallback, listener);
 34                     AllDone.WaitOne();
 35                 }
 36             }
 37             catch (Exception ex)
 38             {
 39                 var path = $"{AppDomain.CurrentDomain.BaseDirectory}\RunLog.txt";
 40                 File.AppendAllText(path, ex.Message);
 41             }
 42         }
 43 
 44 
 45         private static void AcceptCallback(IAsyncResult ar)
 46         {
 47             AllDone.Set();
 48             Socket listener = (Socket)ar.AsyncState;
 49             Socket handler = listener.EndAccept(ar);
 50             ComObject state = new ComObject { WorkSocket = handler };
 51             handler.BeginReceive(state.Buffer, 0, ComObject.BufferSize, 0, FindUpdateFileCallback, state);
 52         }
 53 
 54 
 55         private static void FindUpdateFileCallback(IAsyncResult ar)
 56         {
 57             ComObject state = (ComObject)ar.AsyncState;
 58             Socket handler = state.WorkSocket;
 59             int bytesRead = handler.EndReceive(ar);
 60             if (bytesRead > 0)
 61             {
 62                 var receiveData = state.Buffer.Take(bytesRead).ToArray();
 63                 var dataList = PacketUtils.SplitBytes(receiveData, PacketUtils.ClientFindFileInfoTag());
 64                 if (dataList != null && dataList.Any())
 65                 {
 66                     var request = PacketUtils.GetData(PacketUtils.ClientFindFileInfoTag(), dataList.FirstOrDefault());
 67                     string str = System.Text.Encoding.UTF8.GetString(request);
 68                     var infos = str.Split('_');
 69                     var productName = infos[0];
 70                     var revitVersion = infos[1];
 71                     var currentVersion = infos[2];
 72 
 73                     var mainFolder = AppDomain.CurrentDomain.BaseDirectory.Replace("bin", "TestFile");
 74                     var serverFileFolder = Path.Combine(mainFolder, "Server");
 75                     var serverFileFiles = new DirectoryInfo(serverFileFolder).GetFiles();
 76                    
 77                     var updatefile  = serverFileFiles.FirstOrDefault(x=>x.Name.Contains(productName) && x.Name.Contains(revitVersion) && x.Name.Contains(currentVersion));
 78                     if (updatefile != null)
 79                     {
 80                         if (string.IsNullOrEmpty(updatefile.FullName) || !File.Exists(updatefile.FullName)) return;
 81                         _serverPath = updatefile.FullName;
 82                         FoundUpdateFileResponse(handler);
 83                     }
 84                 }
 85             }
 86         }
 87 
 88 
 89         private static void FoundUpdateFileResponse(Socket handler)
 90         {
 91             byte[] foundUpdateFileData = PacketUtils.PacketData(PacketUtils.ServerFoundFileInfoTag(),null);
 92             ComObject state = new ComObject { WorkSocket = handler };
 93             handler.BeginSend(foundUpdateFileData, 0, foundUpdateFileData.Length, 0, HasFoundUpdateFileCallback, state);
 94         }
 95 
 96 
 97         private static void HasFoundUpdateFileCallback(IAsyncResult ar)
 98         {
 99             ComObject state = (ComObject)ar.AsyncState;
100             Socket handler = state.WorkSocket;
101             handler.EndSend(ar);
102             handler.BeginReceive(state.Buffer, 0, ComObject.BufferSize, 0, ReadFilePositionRequestCallback, state);
103         }
104 
105 
106         private static void ReadFilePositionRequestCallback(IAsyncResult ar)
107         {
108             ComObject state = (ComObject)ar.AsyncState;
109             Socket handler = state.WorkSocket;
110             int bytesRead = handler.EndReceive(ar);
111             if (bytesRead > 0)
112             {
113                 var receiveData = state.Buffer.Take(bytesRead).ToArray();
114                 var dataList = PacketUtils.SplitBytes(receiveData, PacketUtils.ClientRequestFileTag());
115                 if (dataList != null)
116                 {
117                     foreach (var request in dataList)
118                     {
119                         if (PacketUtils.IsPacketComplete(request))
120                         {
121                             int startPosition = PacketUtils.GetRequestFileStartPosition(request); 
122                             SendFileResponse(handler, startPosition);
123                         }
124                     }
125                 }
126             }
127         }
128 
129         private static void SendFileResponse(Socket handler, int startPosition)
130         {
131             var packetSize = PacketUtils.GetPacketSize(_serverPath, _downloadChannelsCount);
132             if (packetSize != 0)
133             {
134                 byte[] filedata = FileUtils.GetFile(_serverPath, startPosition, packetSize);
135                 byte[] packetNumber = BitConverter.GetBytes(startPosition/packetSize);
136                 if (filedata != null)
137                 {
138                     byte[] segmentedFileResponseData = PacketUtils.PacketData(PacketUtils.ServerResponseFileTag(), filedata, packetNumber);
139                     ComObject state = new ComObject {WorkSocket = handler};
140                     handler.BeginSend(segmentedFileResponseData, 0, segmentedFileResponseData.Length, 0, SendFileResponseCallback, state);
141                 }
142             }
143             else
144             {               
145                 handler.Shutdown(SocketShutdown.Both);
146                 handler.Close();
147             }       
148         }
149 
150 
151         private static void SendFileResponseCallback(IAsyncResult ar)
152         {
153             try
154             {
155                 ComObject state = (ComObject)ar.AsyncState;
156                 Socket handler = state.WorkSocket;
157                 handler.EndSend(ar);
158                 handler.Shutdown(SocketShutdown.Both);
159                 handler.Close();             
160             }
161             catch (Exception e)
162             {
163 
164             }
165         }
166     }
167 }

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：

  1 using System;
  2 using System.IO;
  3 using System.Linq;
  4 using System.Net;
  5 using System.Net.Sockets;
  6 using System.Threading;
  7 using UpdaterShare.GlobalSetting;
  8 using UpdaterShare.Model;
  9 using UpdaterShare.Utility;
 10 
 11 namespace UpdaterServerSAEA
 12 {
 13     public class ServerSocket
 14     {
 15         private readonly int _port;
 16         private readonly int _backlog;
 17         private Socket _listenSocket;
 18         private const int _opsToPreAlloc = 2;
 19         private readonly BufferManager _bufferManager;
 20         private readonly SocketAsyncEventArgsPool _readWritePool;
 21         private readonly Semaphore _maxNumberAcceptedClients;
 22 
 23         private string _serverPath;
 24         private static readonly int _downloadChannelsCount = DownloadSetting.DownloadChannelsCount;
 25 
 26         public ServerSocket(int port, int backlog)
 27         {
 28             _port = port;
 29             _backlog = backlog;
 30 
 31             _bufferManager = new BufferManager(ComObject.BufferSize * backlog * _opsToPreAlloc, ComObject.BufferSize);
 32             _readWritePool = new SocketAsyncEventArgsPool(backlog);
 33             _maxNumberAcceptedClients = new Semaphore(backlog, backlog);
 34         }
 35 
 36 
 37         private void Init()
 38         {
 39             _bufferManager.InitBuffer();
 40 
 41             for (var i = 0; i < _backlog; i++)
 42             {
 43                 var readWriteEventArg = new SocketAsyncEventArgs();
 44                 _bufferManager.SetBuffer(readWriteEventArg);
 45                 _readWritePool.Push(readWriteEventArg);
 46             }
 47         }
 48 
 49 
 50         public void StartServer()
 51         {
 52             try
 53             {
 54                 Init();
 55                 IPAddress ipAddress = IPAddress.Any;
 56                 IPEndPoint localEndPoint = new IPEndPoint(ipAddress, _port);
 57                 _listenSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
 58                 _listenSocket.Bind(localEndPoint);
 59                 _listenSocket.Listen(_backlog);
 60                 StartAccept(null);
 61             }
 62             catch (Exception ex)
 63             {
 64                 Console.WriteLine(ex.Message);
 65             }
 66         }
 67 
 68         private void StartAccept(SocketAsyncEventArgs acceptEventArg)
 69         {
 70             if (acceptEventArg == null)
 71             {
 72                 acceptEventArg = new SocketAsyncEventArgs();
 73                 acceptEventArg.Completed += StartAccept_Completed;
 74             }
 75             else
 76             {
 77                 acceptEventArg.AcceptSocket = null;
 78             }
 79 
 80             _maxNumberAcceptedClients.WaitOne();
 81 
 82             if (!_listenSocket.AcceptAsync(acceptEventArg))
 83             {
 84                 ProcessAccept(acceptEventArg);
 85             }
 86         }
 87 
 88         private void StartAccept_Completed(object sender, SocketAsyncEventArgs e)
 89         {
 90             ProcessAccept(e);
 91         }
 92 
 93 
 94         private void ProcessAccept(SocketAsyncEventArgs e)
 95         {
 96             if (e.SocketError == SocketError.Success)
 97             {
 98                 var socket = e.AcceptSocket;
 99                 if (socket.Connected)
100                 {
101                     SocketAsyncEventArgs readEventArgs = _readWritePool.Pop();
102                     readEventArgs.AcceptSocket = socket;
103                     readEventArgs.Completed += ProcessAccept_Completed;
104                     if (!socket.ReceiveAsync(readEventArgs))
105                     {
106                         ProcessReceiveFindFileRequest(readEventArgs);
107                     }
108                     StartAccept(e);
109                 }
110             }
111         }
112 
113         private void ProcessAccept_Completed(object sender, SocketAsyncEventArgs e)
114         {
115             ProcessReceiveFindFileRequest(e);
116         }
117 
118 
119         private void ProcessReceiveFindFileRequest(SocketAsyncEventArgs e)
120         {
121             var bytesRead = e.BytesTransferred;
122             if (bytesRead > 0 && e.SocketError == SocketError.Success)
123             {
124                 var receiveData = e.Buffer.Skip(e.Offset).Take(bytesRead).ToArray();
125                 var dataList = PacketUtils.SplitBytes(receiveData, PacketUtils.ClientFindFileInfoTag());
126                 if (dataList != null && dataList.Any())
127                 {
128                     var request = PacketUtils.GetData(PacketUtils.ClientFindFileInfoTag(), dataList.FirstOrDefault());
129                     string str = System.Text.Encoding.UTF8.GetString(request);
130                     var infos = str.Split('_');
131                     var productName = infos[0];
132                     var revitVersion = infos[1];
133                     var currentVersion = infos[2];
134 
135                     var mainFolder = AppDomain.CurrentDomain.BaseDirectory.Replace("bin", "TestFile");
136                     var serverFileFolder = Path.Combine(mainFolder, "Server");
137                     var serverFileFiles = new DirectoryInfo(serverFileFolder).GetFiles();
138 
139                     var updatefile = serverFileFiles.FirstOrDefault(x => x.Name.Contains(productName) && x.Name.Contains(revitVersion) && x.Name.Contains(currentVersion));
140                     if (updatefile != null)
141                     {
142                         if (string.IsNullOrEmpty(updatefile.FullName) || !File.Exists(updatefile.FullName)) return;
143                         _serverPath = updatefile.FullName;
144 
145                         //ready to send back to Client
146                         byte[] foundUpdateFileData = PacketUtils.PacketData(PacketUtils.ServerFoundFileInfoTag(), null);
147 
148                         Array.Clear(e.Buffer, e.Offset, e.Count);
149                         Array.Copy(foundUpdateFileData, 0, e.Buffer, e.Offset, foundUpdateFileData.Length);
150 
151                         e.Completed -= ProcessAccept_Completed;
152                         e.Completed += ProcessReceiveFindFileRequest_Completed;
153 
154                         if (!e.AcceptSocket.SendAsync(e))
155                         {
156                             ProcessFilePosition(e);
157                         }
158                     }
159                 }
160             }
161         }
162 
163 
164         private void ProcessReceiveFindFileRequest_Completed(object sender, SocketAsyncEventArgs e)
165         {
166             ProcessFilePosition(e);
167         }
168 
169 
170         private void ProcessFilePosition(SocketAsyncEventArgs e)
171         {
172             if (e.SocketError == SocketError.Success)
173             {
174                 var socket = e.AcceptSocket;
175                 if (socket.Connected)
176                 {
177                     //clear buffer
178                     Array.Clear(e.Buffer, e.Offset, e.Count);
179 
180                     e.Completed -= ProcessReceiveFindFileRequest_Completed;
181                     e.Completed += ProcessFilePosition_Completed;
182 
183                     if (!socket.ReceiveAsync(e))
184                     {
185                         ProcessSendFile(e);
186                     }
187                 }
188             }
189         }
190 
191         private void ProcessFilePosition_Completed(object sender, SocketAsyncEventArgs e)
192         {
193             ProcessSendFile(e);
194         }
195 
196         private void ProcessSendFile(SocketAsyncEventArgs e)
197         {
198             var bytesRead = e.BytesTransferred;
199             if (bytesRead > 0 && e.SocketError == SocketError.Success)
200             {
201                 var receiveData = e.Buffer.Skip(e.Offset).Take(bytesRead).ToArray();
202                 var dataList = PacketUtils.SplitBytes(receiveData, PacketUtils.ClientRequestFileTag());
203                 if (dataList != null)
204                 {
205                     foreach (var request in dataList)
206                     {
207                         if (PacketUtils.IsPacketComplete(request))
208                         {
209                             int startPosition = PacketUtils.GetRequestFileStartPosition(request);
210 
211                             var packetSize = PacketUtils.GetPacketSize(_serverPath, _downloadChannelsCount);
212                             if (packetSize != 0)
213                             {
214                                 byte[] filedata = FileUtils.GetFile(_serverPath, startPosition, packetSize);
215                                 byte[] packetNumber = BitConverter.GetBytes(startPosition / packetSize);
216 
217                                 Console.WriteLine("Receive File Request PacketNumber: "+startPosition / packetSize);
218 
219                                 if (filedata != null)
220                                 {
221                                     //ready to send back to Client
222                                     byte[] segmentedFileResponseData = PacketUtils.PacketData(PacketUtils.ServerResponseFileTag(), filedata, packetNumber);
223 
224                                     Array.Clear(e.Buffer, e.Offset, e.Count);
225                                     Array.Copy(segmentedFileResponseData, 0, e.Buffer, e.Offset, segmentedFileResponseData.Length);
226 
227                                     e.Completed -= ProcessFilePosition_Completed;
228                                     e.Completed += ProcessSendFile_Completed;
229 
230                                     if (!e.AcceptSocket.SendAsync(e))
231                                     {
232                                         CloseClientSocket(e);
233                                     }
234                                 }
235                             }
236                         }
237                     }
238                 }
239             }
240             else
241             {
242                 CloseClientSocket(e);
243             }
244         }
245 
246 
247         private void ProcessSendFile_Completed(object sender, SocketAsyncEventArgs e)
248         {
249             CloseClientSocket(e);
250         }
251 
252 
253         private void CloseClientSocket(SocketAsyncEventArgs e)
254         {
255             try
256             {
257                 e.AcceptSocket.Shutdown(SocketShutdown.Both);
258                 e.AcceptSocket.Close();
259             }
260             catch (Exception ex)
261             {
262                 Console.WriteLine(ex.Message);
263             }
264             finally
265             {
266                 _maxNumberAcceptedClients.Release();
267                 _readWritePool.Push(e);
268             }
269         }
270     }
271 }

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