Overlapped I/O模型--事件通知【摘录自《Windows网络编程》】

原文：http://www.cnblogs.com/NeuqUstcIim/archive/2008/08/16/1269479.html
 
重叠I / O的事件通知方法要求将Wi n 3 2事件对象与W S A O V E R L A P P E D结构关联在一起。若使用一个W S A O V E R L A P P E D结构，发出像W S A S e n d和W S A R e c v这样的I / O调用，它们会立即返回。

    一个重叠I / O请求最终完成后，我们的应用程序要负责取回重叠I / O操作的结果。一个重叠请求操作最终完成之后，在事件通知方法中， Wi n s o c k会更改与一个W S A O V E R L A P P E D结构对应的一个事件对象的事件传信状态，将其从“未传信”变成“已传信”。 由于一个事件对象

已分配给W S A O V E R L A P P E D结构，所以只需简单地调用W S AWa i t F o r M u l t i p l e E v e n t s函数，从而判断出一个重叠I / O调用在什么时候完成。

   注意： W S AWa i t F o r M u l t i p l e E v e n t s返回只是说明重叠IO操作完成，但是是成功的完成还是失败的完成还要调用W S A G e t O v e r l a p p e dR e s u l t（取得重叠结构）函数

    如W S A G e t O v e r l a p p e d R e s u l t函数调用成功，返回值就是T R U E。这意味着我们的重叠I / O操作已成功完成，而且由l p c b Tr a n s f e r参数指向的值已进行了更新。

 

   我们向大家阐述了如何编制一个简单的服务器应用，令其在一个套接字上对重叠I / O操作进行管理，程序完全利用了前述的事件通知机制。对该程序采用的编程步骤总结如下：
1) 创建一个套接字，开始在指定的端口上监听连接请求。
2) 接受一个进入的连接请求。
3) 为接受的套接字新建一个W S A O V E R L A P P E D结构，并为该结构分配一个事件对象句柄。也将事件对象句柄分配给一个事件数组，以便稍后由W S AWa i t F o r M u l t i p l e E v e n t s函数使用。
4) 在套接字上投递一个异步W S A R e c v请求，指定参数为W S A O V E R L A P P E D结构。
注意函数通常会以失败告终，返回S O C K E T _ E R R O R错误状态W S A _ I O _ P E N D I N G
（I/O操作尚未完成）。
5) 使用步骤3 )的事件数组，调用W S AWa i t F o r M u l t i p l e E v e n t s函数，并等待与重叠调用关联在一起的事件进入“已传信”状态（换言之，等待那个事件的“触发”）。
6) WSAWa i t F o r M u l t i p l e E v e n t s函数完成后，针对事件数组，调用W S A R e s e t E v e n t（重设事件）函数，从而重设事件对象，并对完成的重叠请求进行处理。
7) 使用W S A G e t O v e r l a p p e d R e s u l t函数，判断重叠调用的返回状态是什么。
8) 在套接字上投递另一个重叠W S A R e c v请求。

9) 重复步骤5 ) ~ 8 )。


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  1. #include "stdafx.h"
  2.  #include <winsock2.h>

  4.  #define DATA_BUFSIZE 4096

  6.  #pragma comment(lib, "ws2_32.lib")

  8.  int _tmain(int argc, _TCHAR* argv[])
  9.  {
  10.      DWORD EventTotal = 0,RecvBytes = 0, Flags = 0;
  11.      char buffer[DATA_BUFSIZE];

  13.      WSABUF DataBuf;
  14.      WSAEVENT EventArray[WSA_MAXIMUM_WAIT_EVENTS];
  15.      WSAOVERLAPPED AcceptOverlapped;
  16.      SOCKET Listen,Accept;

  18.      //step1:
  19.      //start Winsock and set up a listening socket
  20.      WSADATA wsaData;
  21.      WSAStartup(MAKEWORD(2,2), &wsaData);

  23.      ListenSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
  24.      u_short port = 27015;
  25.      char* ip;
  26.      sockaddr_in service;
  27.      service.sin_family = AF_INET;
  28.      service.sin_port = htons(port);
  29.      hostent* thisHost;
  30.      thisHost = gethostbyname("");
  31.      ip = inet_ntoa (*(struct in_addr *)*thisHost->h_addr_list);

  33.      service.sin_addr.s_addr = inet_addr(ip);

  35.      //-----------------------------------------
  36.      // Bind the listening socket to the local IP address
  37.      // and port number
  38.      bind(ListenSocket, (SOCKADDR *) &service, sizeof(SOCKADDR));

  40.      //-----------------------------------------
  41.      // Set the socket to listen for incoming
  42.      // connection requests
  43.      listen(ListenSocket, 1);
  44.      printf("Listening\n");

  46.      //step2:
  47.      Accept=accept(Listen,NULL,NULL);

  49.      //step3:
  50.      //set up an overlapped structure
  51.      EventArray[EventTotal]=WSACreateEvent();//先存到事件数组中
  52.      ZeroMemory(&AcceptOverlapped,sizeof(WSAOVERLAPPED));
  53.      AcceptOverlapped.hEvent = EventArray[EventTotal];

  55.      DataBuf.len = DATA_BUFSIZE;
  56.      DataBuf.buf =buffer;

  58.      EventTotal++;

  60.      //step4:
  61.      //投递WSARecv准备在Accept套接字上接收数据
  62.      WSARecv(Accept,&DataBuf,1,&RecvBytes,&Flag,&AcceptOverlapped,NULL);

  64.      while (TRUE){
  65.          //step5:
  66.          //等待overlapped IO调用的完成
  67.          DWORD Index;
  68.          Index = WSAWaitForMultipleEvents(EventTotal, EventArray, FALSE, WSA_INFINITE, FALSE);

  70.          //step6:
  71.          // Reset the signaled event
  72.          WSAResetEvent(EventArray[Index - WSA_WAIT_EVENT_0]);

  74.          //step7:
  75.          // Determine the status of the overlapped event
  76.          WSAGetOverlappedResult(AcceptSocket, &AcceptOverlapped, &BytesTransferred, FALSE, &Flags);


  79.          // If the connection has been closed, close the accepted socket
  80.          if (BytesTransferred == 0) {
  81.              printf("Closing Socket %d\n", AcceptSocket);
  82.              closesocket(AcceptSocket);
  83.              WSACloseEvent(EventArray[Index - WSA_WAIT_EVENT_0]);
  84.              return;
  85.          }

  87.          // If data has been received,do something with received data
  88.          //DataBuf contains the received data

  90.          //step8:
  91.          //post another WSARecv () request on the socket
  92.          Flag=0;
  93.          ZeroMemory(&AcceptOverlapped,sizeof(WSAOVERLAPPED));
  94.          AcceptOverlapped.hEvent=EventArray[Index - WSA_WAIT_EVENT_0];//该事件对象已经被复位

  96.          DataBuf.len = DATA_BUFSIZE;
  97.          DataBuf.buf =buffer;

  99.          WSARecv(Accept,&DataBuf,1,&RecvBytes,&Flag,&AcceptOverlapped,NULL);
  100.      }
  101.      return 0;
  102.  }

改进后的程序（并非实际可以运行的程序，只是为了理清思路）：

点击(此处)折叠或打开

  1. #define LISTEN_PORT 5000
  2.  #define DATA_BUFSIZE 8192
  3.  #define POST_RECV 0X01
  4.  #define POST_SEND 0X02

  6.  int main( )
  7.  {
  8.      LPPER_HANDLE_DATA lpPerHandleData;
  9.      SOCKET hListenSocket;
  10.      SOCKET hClientSocket;
  11.      SOCKADDR_IN ClientAddr;
  12.      int nAddrLen;
  13.      HANDLE hThread;

  15.      // Start WinSock and create a listen socket.

  17.      listen(hListenSocket, 5);
  18.      for (; ;)
  19.      {
  20.          nAddrLen = sizeof(SOCKADDR);
  21.          hClientSocket = accept(hListenSocket, (LPSOCKADDR)&ClientAddr, &nAddrLen);

  23.          lpPerHandleData = (LPPER_HANDLE_DATA)malloc(sizeof(PER_HANDLE_DATA));
  24.          lpPerHandleData->hSocket = hClientSocket;
  25.          // 注意这里将连接的客户端的IP地址，保存到了lpPerHandleData字段中了
  26.          strcpy(lpPerHandleData->szClientIP, inet_ntoa(ClientAddr.sin_addr));

  28.          // 为本次客户请求产生子线程
  29.          hThread = CreateThread(
  30.              NULL,
  31.              0,
  32.              OverlappedThread,
  33.              lpPerHandleData, // 将lpPerHandleData传给子线程
  34.              0,
  35.              NULL
  36.              );
  37.          CloseHandle(hThread);
  38.      }
  39.      return 0;
  40.  }

  42.  DWORD WINAPI OverlappedThread(LPVOID lpParam)
  43.  {
  44.      LPPER_HANDLE_DATA lpPerHandleData = (LPPER_HANDLE_DATA)lpParam;
  45.      WSAOVERLAPPED Overlapped;
  46.      WSABUF wsaBuf;
  47.      WSAEVENT EventArray[WSA_MAXIMUM_WAIT_EVENTS];//事件对象数组

  49.      DWORD dwEventTotal = 0, // 程序中事件的总数
  50.      char Buffer[DATA_BUFSIZE];
  51.      BOOL bResult;
  52.      int nResult;

  54.      EventArray[dwEventTotal] = WSACreateEvent();

  56.      ZeroMemory(&Overlapped, sizeof(WSAOVERLAPPED));

  58.      Overlapped.hEvent = EventArray[dwEventTotal]; // 关联事件

  60.      ZeroMemory(Buffer, DATA_BUFSIZE);
  61.      wsaBuf.buf = Buffer;
  62.      wsaBuf.len = sizeof(Buffer);
  63.      
  64.      lpPerHandleData->nOperateType = POST_RECV; // 记录本次操作是Recv(..)

  66.      dwEventTotal ++; // 总数加一
  67.      dwFlags = 0;

  69.      nResult = WSARecv(
  70.          lpPerHandleData->hSocket, // Receive socket
  71.          &wsaBuf, // 指向WSABUF结构的指针
  72.          1, // WSABUF数组的个数
  73.          &dwNumOfBytesRecved, // 存放当WSARecv完成后所接收到的字节数,实际接收到的字节数
  74.          &dwFlags, // A pointer to flags
  75.          &Overlapped, // A pointer to a WSAOVERLAPPED structure
  76.          NULL // A pointer to the completion routine,this is NULL
  77.          );

  79.      if ( nResult == SOCKET_ERROR && GetLastError() != WSA_IO_PENDING)
  80.      {
  81.          printf("WSARecv(..) failed.\n");
  82.          free(lpPerHandleData);

  84.          closesocket(lpPerHandleData->hSocket;
  85.           WSACloseEvent(EventArray[dwEventTotal]);
  86.          return -1;
  87.      }

  89.      while (TRUE)
  90.      {
  91.          DWORD dwIndex;

  93.          dwIndex = WSAWaitForMultipleEvents(dwEventTotal, EventArray ,
  94.              FALSE ,WSA_INFINITE,FALSE);

  96.         WSAResetEvent(EventArray[dwIndex– WSA_WAIT_EVENT_0]);


  99.          bResult = WSAGetOverlappedResult(
  100.              lpPerHandleData->hSocket,
  101.              &Overlapped,
  102.              &dwBytesTransferred, // 当一个同步I/O完成后,接收到的字节数
  103.              TRUE, // 等待I/O操作的完成
  104.              &dwFlags
  105.              );
  106.          if (bResult == FALSE && WSAGetLastError() != WSA_IO_INCOMPLETE)
  107.          {
  108.              printf("WSAGetOverlappdResult(..) failed.\n");
  109.              free(lpPerHandleData);
  110.              return 0; // 错误退出
  111.          }

  113.          if (dwBytesTransferred == 0)
  114.          {
  115.              printf("客户端已退出,将断开与之的连接!\n");
  116.              closesocket(lpPerHandleData->hSocket);
  117.              free(lpPerHandleData);
  118.              break;
  119.          }

  121.          // 在这里将接收到的数据进行处理
  122.          printf("Received from IP: %s.\ndata: %s\n", lpPerHandleData->szClientIP, wsaBuf.buf);

  124.          // 发送另外一个请求操作
  125.          ZeroMemory(&Overlapped, sizeof(WSAOVERLAPPED));
  126.          lpPerHandleData->nOperateType = POST_RECV;

  128.          dwFlags = 0;
  129.          nResult = WSARecv();
  130.          if (){}

  132.      }

  134.      return 1;
  135.  }

最后的一个改进版本，看上去是个不错的版本，相对来说算是比较实用的。但是使用了过多的全局变量，代码是C风格的，不可取。

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  1. #include <winsock2.h>
  2.  #include <stdio.h>

  4.  #define PORT 5150
  5.  #define MSGSIZE 1024

  7.  #pragma comment(lib, "ws2_32.lib")

  9.  typedef struct
  10.  {
  11.  WSAOVERLAPPED overlap;
  12.  WSABUF Buffer;
  13.  char szMessage[MSGSIZE];
  14.  DWORD NumberOfBytesRecvd;
  15.  DWORD Flags;
  16.  }PER_IO_OPERATION_DATA, *LPPER_IO_OPERATION_DATA;

  18.  int g_iTotalConn = 0;
  19.  SOCKET g_CliSocketArr[MAXIMUM_WAIT_OBJECTS];
  20.  WSAEVENT g_CliEventArr[MAXIMUM_WAIT_OBJECTS];
  21.  LPPER_IO_OPERATION_DATA g_pPerIODataArr[MAXIMUM_WAIT_OBJECTS];

  23.  DWORD WINAPI WorkerThread(LPVOID);

  25.  void Cleanup(int);

  27.  int main()
  28.  {
  29.  WSADATA wsaData;
  30.  SOCKET sListen, sClient;
  31.  SOCKADDR_IN local, client;
  32.  DWORD dwThreadId;
  33.  int iaddrSize = sizeof(SOCKADDR_IN);
  34.  // Initialize Windows Socket library
  35.  WSAStartup(0x0202, &wsaData);
  36.  // Create listening socket
  37.  sListen = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
  38.  // Bind
  39.  local.sin_addr.S_un.S_addr = htonl(INADDR_ANY);
  40.  local.sin_family = AF_INET;
  41.  local.sin_port = htons(PORT);
  42.  bind(sListen, (struct sockaddr *)&local, sizeof(SOCKADDR_IN));
  43.  // Listen
  44.  listen(sListen, 3);


  47. //网上的代码如此，好奇怪，为什么是在连接还没开始的时候就创建一个线程，而不是像上面的程序一样，accept一个
  48. //connection创建一个线程，并将从connection 的socket中获取的信息当作形参传递给workThread?
  49. //这里是只创建一个线程为重叠socket I/O操作服务
  50.  // Create worker thread
  51.  CreateThread(NULL, 0, WorkerThread, NULL, 0, &dwThreadId);
  52.  while (TRUE)
  53.  {
  54.      // Accept a connection
  55.      sClient = accept(sListen, (struct sockaddr *)&client, &iaddrSize);

  57.          //这很好，在accept函数中的后两个形参中获取client的相关信息，并直接在server端的控制台中显示出来
  58.      printf("Accepted client:%s:%d\n", inet_ntoa(client.sin_addr), ntohs(client.sin_port));
  59.      g_CliSocketArr[g_iTotalConn] = sClient;//添加到socket数组中
  60.     
  61.      // Allocate a PER_IO_OPERATION_DATA structure
  62.      g_pPerIODataArr[g_iTotalConn] = ER(LPPER_IO_OPATION_DATA)HeapAlloc(
  63.               GetProcessHeap(),HEAP_ZERO_MEMORY,sizeof(PER_IO_OPERATION_DATA));
  64.      g_pPerIODataArr[g_iTotalConn]->Buffer.len = MSGSIZE;
  65.      g_pPerIODataArr[g_iTotalConn]->Buffer.buf = g_pPerIODataArr[g_iTotalConn]->eszMssage;
  66.      g_CliEventArr[g_iTotalConn] = g_pPerIODataArr[g_iTotalConn]->overlap.hEvent = WSACreateEvent();
  67.      // Launch an asynchronous operation
  68.      WSARecv(
  69.        g_CliSocketArr[g_iTotalConn],
  70.        &g_pPerIODataArr[g_iTotalConn]->Buffer,
  71.        1,
  72.        &g_pPerIODataArr[g_iTotalConn]->NumberOfBytesRecvd,
  73.        &g_pPerIODataArr[g_iTotalConn]->Flags,
  74.        &g_pPerIODataArr[g_iTotalConn]->overlap,
  75.        NULL);
  76.     
  77.      g_iTotalConn++;
  78.  }

  80.  closesocket(sListen);
  81.  WSACleanup();
  82.  return 0;
  83.  }
  84.  DWORD WINAPI WorkerThread(LPVOID lpParam)
  85.  {
  86.  int ret, index;
  87.  DWORD cbTransferred;
  88.  while (TRUE)
  89.  {
  90.      ret = WSAWaitForMultipleEvents(g_iTotalConn, g_CliEventArr, FALSE, 1000, FALSE);
  91.      if (ret == WSA_WAIT_FAILED || ret == WSA_WAIT_TIMEOUT)
  92.      {
  93.        continue;
  94.      }
  95.      index = ret - WSA_WAIT_EVENT_0;
  96.      WSAResetEvent(g_CliEventArr[index]);
  97.      WSAGetOverlappedResult(
  98.        g_CliSocketArr[index],
  99.        &g_pPerIODataArr[index]->overlap,
  100.        &cbTransferred,
  101.        TRUE,
  102.        &g_pPerIODataArr[g_iTotalConn]->Flags);
  103.      if (cbTransferred == 0)
  104.      {
  105.        // The connection was closed by client
  106.        Cleanup(index);
  107.      }
  108.      else
  109.      {
  110.        // g_pPerIODataArr[index]->szMessage contains the received data
  111.        g_pPerIODataArr[index]->szMessage[cbTransferred] = '\0';
  112.        send(g_CliSocketArr[index], g_pPerIODataArr[index]->szMessage,\
  113.          cbTransferred, 0);
  114.        // Launch another asynchronous operation
  115.        WSARecv(
  116.          g_CliSocketArr[index],
  117.          &g_pPerIODataArr[index]->Buffer,
  118.          1,
  119.          &g_pPerIODataArr[index]->NumberOfBytesRecvd,
  120.          &g_pPerIODataArr[index]->Flags,
  121.          &g_pPerIODataArr[index]->overlap,
  122.          NULL);
  123.      }
  124.  }
  125.  return 0;
  126.  }
  127.  void Cleanup(int index)
  128.  {
  129.  closesocket(g_CliSocketArr[index]);
  130.  WSACloseEvent(g_CliEventArr[index]);
  131.  HeapFree(GetProcessHeap(), 0, g_pPerIODataArr[index]);
  132.  if (index < g_iTotalConn - 1)
  133.  {
  134.      g_CliSocketArr[index] = g_CliSocketArr[g_iTotalConn - 1];
  135.      g_CliEventArr[index] = g_CliEventArr[g_iTotalConn - 1];
  136.      g_pPerIODataArr[index] = g_pPerIODataArr[g_iTotalConn - 1];
  137.  }
  138.  g_pPerIODataArr[--g_iTotalConn] = NULL;
  139.  }

    这个模型与上述其他模型不同的是它使用Winsock2提供的异步I/O函数WSARecv。在调用WSARecv时，指定一个WSAOVERLAPPED结构，这个调用不是阻塞的，也就是说，它会立刻返回。一旦有数据到达的时候，被指定的WSAOVERLAPPED结构中的hEvent被Signaled。由于下面这个语句g_CliEventArr[g_iTotalConn] = g_pPerIODataArr[g_iTotalConn]->overlap.hEvent；

    使得与该套接字相关联的WSAEVENT对象也被Signaled，所以WSAWaitForMultipleEvents的调用操作成功返回。我们现在应该做的就是与调用WSARecv相同的WSAOVERLAPPED结构为参数调用WSAGetOverlappedResult，从而得到本次I/O传送的字节数等相关信息。在取得接收的数据后，把数据原封不动的发送到客户端，然后重新激活一个WSARecv异步操作。

 

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