异步tcp通信——APM.Core 服务端概述

为什么使用异步

　　异步线程是由线程池负责管理，而多线程，我们可以自己控制，当然在多线程中我们也可以使用线程池。就拿网络扒虫而言，如果使用异步模式去实现，它使用线程池进行管理。异步操作执行时，会将操作丢给线程池中的某个工作线程来完成。当开始I/O操作的时候，异步会将工作线程还给线程池，这意味着获取网页的工作不会再占用任何CPU资源了。直到异步完成，即获取网页完毕，异步才会通过回调的方式通知线程池。可见，异步模式借助于线程池，极大地节约了CPU的资源。
　　注：DMA（Direct Memory Access）直接内存存取，顾名思义DMA功能就是让设备可以绕过处理器，直接由内存来读取资料。通过直接内存访问的数据交换几乎可以不损耗CPU的资源。在硬件中，硬盘、网卡、声卡、显卡等都有直接内存访问功能。异步编程模型就是让我们充分利用硬件的直接内存访问功能来释放CPU的压力。
　　两者的应用场景：
　　　　计算密集型工作，采用多线程。
　　　　IO密集型工作，采用异步机制。

C#中实现异步tcp通信

　　socket中仅仅需要将Blocking=false即可轻松实现异步，部分示例如下：

 1 /// <summary>
 2         /// 启动tcp监听
 3         /// </summary>
 4         public void Start()
 5         {
 6             if (!_isStarted)
 7             {
 8                 _isStarted = true;
 9                 _server = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
10
11                 #region socket配置
12                 LingerOption lingerOption = new LingerOption(true, 30);
13                 _server.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.Linger, lingerOption);
14                 #endregion
15
16                 _server.Blocking = false;
17                 _server.ExclusiveAddressUse = false;
18                 _server.Bind(new IPEndPoint(IPAddress.Any, this._port));
19                 _server.Listen(1000000);
20                 Parallel.For(0, 1000000, i =>
21                 {
22                     _server.BeginAccept(new AsyncCallback(ProcessAccept), _server);
23                 });
24             }
25         }

　　tcp异步中处理接io操作最关键的参数：IAsyncResult，使用一般用begin开始，end结束。

　　接收数据处理如下：

 1 /// <summary>
 2         /// 处理传入的连接请求
 3         /// </summary>
 4         private void ProcessAccept(IAsyncResult ar)
 5         {
 6             var s = (Socket)ar.AsyncState;
 7             var remote = s.EndAccept(ar);
 8             var user = new UserToken(this._maxBufferSize) { ID = remote.RemoteEndPoint.ToString(), Client = remote };
 9             remote.BeginReceive(user.ReceiveBuffer, 0, user.ReceiveBuffer.Length, SocketFlags.None, new AsyncCallback(ProcessReceive),
10                 user);
11             s.BeginAccept(new AsyncCallback(ProcessAccept), s);
12         }

 1 private void ProcessReceive(IAsyncResult ar)
 2         {
 3             var user = (UserToken)ar.AsyncState;
 4             var remote = user.Client;
 5             try
 6             {
 7                 if (remote.Connected)
 8                 {
 9                     var ns = remote.EndReceive(ar);
10
11                     if (ns > 0)
12                     {
13                         var buffer = new byte[ns];
14
15                         Buffer.BlockCopy(user.ReceiveBuffer, 0, buffer, 0, buffer.Length);
16
17                         user.UnPackage(buffer, (p) =>
18                         {
19                             Interlocked.Increment(ref this._receiveCount);
20                             this.RaiseOnOnReceived(user, p);
21                         });
22
23                         user.ClearReceiveBuffer();
24
25                         buffer = null;
26
27                         remote.BeginReceive(user.ReceiveBuffer, 0, user.ReceiveBuffer.Length, SocketFlags.None, new AsyncCallback(ProcessReceive), user);
28                     }
29                 }
30                 else
31                 {
32                     this.RaiseOnDisConnected(user, new Exception("客户端已断开连接"));
33                     this.CloseClient(user);
34                 }
35             }
36             catch (SocketException sex)
37             {
38                 this.RaiseOnDisConnected(user, sex);
39                 this.CloseClient(user);
40             }
41             catch (Exception ex)
42             {
43                 this.RaiseOnError(user, ex);
44                 this.CloseClient(user);
45             }
46         }

　　发送数据处理如下：

 1 /// <summary>
 2         /// 发送信息
 3         /// </summary>
 4         /// <param name="remote"></param>
 5         /// <param name="data"></param>
 6         /// <param name="type"></param>
 7         /// <param name="auth"></param>
 8         private void SendAsync(UserToken remote, byte[] data, TransportType type = TransportType.Heart)
 9         {
10             try
11             {
12                 using (var pakage = new TcpPackage(data, type, remote.Auth))
13                 {
14                     remote.Client.BeginSend(pakage.Data, 0, pakage.Data.Length, SocketFlags.None, new AsyncCallback(EndSend), remote);
15                 }
16
17             }
18             catch (SocketException sex)
19             {
20                 this.RaiseOnDisConnected(remote, sex);
21             }
22             catch (Exception ex)
23             {
24                 this.RaiseOnError(remote, ex);
25             }
26         }

1 private void EndSend(IAsyncResult ar)
2         {
3             var remote = (UserToken)ar.AsyncState;
4             remote.Client.EndSend(ar);
5             Interlocked.Increment(ref this._sendCount);
6         }

　　心跳、消息、文件等逻辑都可以基于发送逻辑来完成

1 /// <summary>
2         /// 回复心跳
3         /// </summary>
4         /// <param name="remote"></param>
5         /// <param name="package"></param>
6         private void ReplyHeart(UserToken remote, TcpPackage package)
7         {
8             this.SendAsync(remote, null, TransportType.Heart);
9         }

1 /// <summary>
2         /// 发送信息
3         /// </summary>
4         /// <param name="remote"></param>
5         /// <param name="msg"></param>
6         public void SendMsg(UserToken remote, byte[] msg)
7         {
8             this.SendAsync(remote, msg, TransportType.Message);
9         }

 1 /// <summary>
 2         /// 发送文件
 3         /// </summary>
 4         /// <param name="remote"></param>
 5         /// <param name="filePath"></param>
 6         public void SendFile(UserToken remote, string filePath)
 7         {
 8             using (var file = new TransferFileInfo()
 9             {
10                 ID = remote.ID,
11                 FileBytes = File.ReadAllBytes(filePath),
12                 Name = filePath.Substring(filePath.LastIndexOf("\\") + 1),
13                 CreateTime = DateTime.Now.Ticks
14             })
15             {
16                 var buffer = TransferFileInfo.Serialize(file);
17                 this.SendAsync(remote, buffer, TransportType.File);
18                 buffer = null;
19             }
20         }

 1 /// <summary>
 2         /// 发送文件
 3         /// </summary>
 4         /// <param name="remote"></param>
 5         /// <param name="fileName"></param>
 6         /// <param name="file"></param>
 7         public void SendFile(UserToken remote, string fileName, byte[] file)
 8         {
 9             using (var fileInfo = new TransferFileInfo()
10             {
11                 ID = remote.ID,
12                 FileBytes = file,
13                 Name = fileName,
14                 CreateTime = DateTime.Now.Ticks
15             })
16             {
17                 var buffer = TransferFileInfo.Serialize(fileInfo);
18                 this.SendAsync(remote, buffer, TransportType.File);
19                 buffer = null;
20             }
21         }