【Socket】蒼老師有了丈夫，我也有了SAEA

一、前言時間過得真是快，轉眼就2018年了。首先祝各位博友，軟體開發者新年新氣象，事業有成，身體健康，闔家幸福！最近看到園子里好多關於自己的2017年度總結以及對自己新一年的願景，覺得咱園子的氛圍是真的好。這三天假期我也沒閑著，一邊看OB海鮮團吃雞一邊寫Socket SocketAsyncEven ...

一、前言

時間過得真是快，轉眼就2018年了。首先祝各位博友，軟體開發者新年新氣象，事業有成，身體健康，闔家幸福！最近看到園子里好多關於自己的2017年度總結以及對自己新一年的願景，覺得咱園子的氛圍是真的好。這三天假期我也沒閑著，一邊看OB海鮮團吃雞一邊寫Socket SocketAsyncEventArgs 代碼。我上一篇博客已經用APM的方式實現了客戶端與伺服器端的Socket通信，並具有了一定的併發能力。所以這三天我就決定對伺服器代碼進行改造，使用MS在4.0時發佈的SocketAsyncEventArgs（SAEA）寫法。為了方便的進行伺服器端兩種寫法的對比，我客戶端的代碼沒有進行變化，依然使用APM方式。代碼已經上傳至Github，鏈接會在文末貼出。

二、我的業務功能

我的業務功能依然是實現從伺服器多線程下載更新文件。下載之前的那些操作我基本就不講了，上一篇博文里的都有，本文還是回到Socket下載文件上。具體流程如下：

在我寫SAEA代碼之前，我仔細搜了一下網上的資源：MSDN、CNBLOG、CSDN、CodeProject。這四種來源的代碼示例的主要流程是這樣的：

對比我的流程，您會發現少了一半的通信過程。客戶端的代碼好寫，但是伺服器端如何發送完數據之後再接收數據？這中間的銜接過程還是有點門道的。特別是SAEA的代碼採用了Buffer池化以及SAEA池化之後，裡面有些小的細節就要想清楚了。下麵就是具體的代碼，我會以我自己的視角去論述APM與SAEA到底有什麼區別。

三、對比

其實對於伺服器端的APM，我覺得最重要的並不是代碼中的BeginXXX或者是EndXXX，因為這就是APM寫法的特征，BeginXXX或者EndXXX然後裡面有一個回調函數，在回調函數里去做一些業務上的事情。最重要的是要有一個線程等待的概念，也就是代碼中的ManualResetEvent這個東西，它就像地鐵閘機一樣，處理好一個再放一個進去。APM寫法的好處是顯而易見的，就是代碼看起來十分的簡單。缺點依照MS的說法就是如果有過多的客-服交流，可能會產生較多的IAsyncResult對象，這樣會增加伺服器的開銷。

伺服器端的APM寫法：

  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 }

說到SAEA，我覺得初入的小伙伴一定要先看MSDN上的實例，特別是它的BufferManager以及SocketAsyncEventArgsPool是怎麼寫的，到底是乾什麼用的。這裡我可以簡單的說下：SocketAsyncEventArgsPool是用來存放SAEA對象的，其個數依賴於你伺服器所能承擔的隊列長度，比如說我伺服器能承擔100個客戶的等待，我就在伺服器端生成100個SAEA對象放在池子里，當有客戶來連接時，我從池子里取出一個來和他對接。客戶走了，我再扔到池子里去。BufferManager則是對池子里的SAEA對象進行Buffer分配的，也相當於一個池子，這個池子的大小是隊列長度*通信緩存長度*2，乘以2是因為讀與寫是分開的。通信緩存長度很好理解，客戶端要傳個2G的信息給伺服器端不可能一下子接收2G，肯定是一口一口吃，那麼這一口的大小就是通信緩存長度。那麼分配給每個SAEA的緩存是多大呢？當然就是通信緩存長度的大小咯。註意！！註意！！註意！！既然是池化了，所有關於Buffer的操作都要圍繞分配給SAEA的Buffer去操作！見148-149行。當伺服器拿著分配到的Buffer去接收信息後，如果再要發送信息，所要做的第一件事就是先清空分配的Buffer再使用，BufferManager給你分配哪段你就用哪段，別使用錯了。有幾個參數需要註意：e.Offset（偏移），e.Count（大小），e.Buffer（緩存位元組數組）， e.BytesTransferred（通信傳輸的位元組長度）。如果伺服器端要發送數據，一定要用Array.Copy將信息寫入對應分配的Buffer中。

說完池化，接著就是寫法上的小區別，我覺得區別並不大，無非就是委托換了個寫法。當然還要判斷下是否為非同步操作，如果是否則需要進行同步操作，見82-85行代碼。

伺服器的SAEA寫法：

  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