完成端口WSARecv作用分析
编写完成端口服务程序，主要就是以下几个步骤：
1、创建一个完成端口
2、根据CPU个数创建工作者线程，把完成端口传进去线程里
3、创建侦听SOCKET，把SOCKET和完成端口关联起来,并投递一个WSARecv操作
4、创建PerIOData，向连接进来的SOCKET投递WSARecv操作
5、线程里所做的事情：
a、GetQueuedCompletionStatus，在退出的时候就可以使用PostQueudCompletionStatus使线程退出
b、取得数据并处理
问题是小弟现在不是很明白第三步中在与完成端口关联后,投递一个WSARecv操作的作用是什么?或者说实际做了一个什么动作?
/* 完成端口服务器 接收到客户端的信息，直接显示出来*/#include "winerror.h"#include "Winsock2.h"#pragma comment(lib, "ws2_32")#include "windows.h"#include <iostream>using namespace std;/// 宏定义#define PORT 5050#define DATA_BUFSIZE 8192#define OutErr(a) cout << (a) << endl << "出错代码：" << WSAGetLastError() << endl << "出错文件：" << __FILE__ << endl << "出错行数：" << __LINE__ << endl#define OutMsg(a) cout << (a) << endl;/// 全局函数定义/////////////////////////////////////////////////////////////////////////// 函数名 : InitWinsock// 功能描述 : 初始化WINSOCK// 返回值 : void/////////////////////////////////////////////////////////////////////////void InitWinsock(){ // 初始化WINSOCK WSADATA wsd; if( WSAStartup(MAKEWORD(2, 2), &wsd) != 0) }/////////////////////////////////////////////////////////////////////////// 函数名 : BindServerOverlapped// 功能描述 : 绑定端口，并返回一个 Overlapped 的Listen Socket// 参数 : int nPort// 返回值 : SOCKET/////////////////////////////////////////////////////////////////////////SOCKET BindServerOverlapped(int nPort){ // 创建socket SOCKET sServer = WSASocket(AF_INET, SOCK_STREAM, 0, NULL, 0, WSA_FLAG_OVERLAPPED); // 绑定端口 struct sockaddr_in servAddr; servAddr.sin_family = AF_INET; servAddr.sin_port = htons(nPort); servAddr.sin_addr.s_addr = htonl(INADDR_ANY); if(bind(sServer, (struct sockaddr *)&servAddr, sizeof(servAddr)) < 0) { OutErr("bind Failed!"); return NULL; } // 设置监听队列为200 if(listen(sServer, 200) != 0) { OutErr("listen Failed!"); return NULL; } return sServer;}/// 结构体定义typedef struct{ OVERLAPPED Overlapped; WSABUF DataBuf; CHAR Buffer[DATA_BUFSIZE];} PER_IO_OPERATION_DATA, * LPPER_IO_OPERATION_DATA;typedef struct{ SOCKET Socket;} PER_HANDLE_DATA, * LPPER_HANDLE_DATA;DWORD WINAPI ProcessIO(LPVOID lpParam){ HANDLE CompletionPort = (HANDLE)lpParam; DWORD BytesTransferred; LPPER_HANDLE_DATA PerHandleData; LPPER_IO_OPERATION_DATA PerIoData; while(true) { if(0 == GetQueuedCompletionStatus(CompletionPort, &BytesTransferred, (LPDWORD)&PerHandleData, (LPOVERLAPPED*)&PerIoData, INFINITE)) { if( (GetLastError() == WAIT_TIMEOUT) || (GetLastError() == ERROR_NETNAME_DELETED) ) { cout << "closing socket" << PerHandleData->Socket << endl; closesocket(PerHandleData->Socket); delete PerIoData; delete PerHandleData; continue; } else { OutErr("GetQueuedCompletionStatus failed!"); } return 0; } // 说明客户端已经退出 if(BytesTransferred == 0) { cout << "closing socket" << PerHandleData->Socket << endl; closesocket(PerHandleData->Socket); delete PerIoData; delete PerHandleData; continue; } // 取得数据并处理 cout << PerHandleData->Socket << "发送过来的消息：" << PerIoData->Buffer << endl; // 继续向 socket 投递WSARecv操作 DWORD Flags = 0; DWORD dwRecv = 0; ZeroMemory(PerIoData, sizeof(PER_IO_OPERATION_DATA)); PerIoData->DataBuf.buf = PerIoData->Buffer; PerIoData->DataBuf.len = DATA_BUFSIZE; WSARecv(PerHandleData->Socket, &PerIoData->DataBuf, 1, &dwRecv, &Flags, &PerIoData->Overlapped, NULL); } return 0;}void main(){ InitWinsock(); HANDLE CompletionPort = CreateIoCompletionPort(INVALID_HANDLE_VALUE, NULL, 0, 0); // 根据系统的CPU来创建工作者线程 SYSTEM_INFO SystemInfo; GetSystemInfo(&SystemInfo); for(int i = 0; i < SystemInfo.dwNumberOfProcessors * 2; i++) { HANDLE hProcessIO = CreateThread(NULL, 0, ProcessIO, CompletionPort, 0, NULL); if(hProcessIO) } // 创建侦听SOCKET SOCKET sListen = BindServerOverlapped(PORT); SOCKET sClient; LPPER_HANDLE_DATA PerHandleData; LPPER_IO_OPERATION_DATA PerIoData; while(true) { // 等待客户端接入 //sClient = WSAAccept(sListen, NULL, NULL, NULL, 0); sClient = accept(sListen, 0, 0); cout << "Socket " << sClient << "连接进来" << endl; PerHandleData = new PER_HANDLE_DATA(); PerHandleData->Socket = sClient; // 将接入的客户端和完成端口联系起来 CreateIoCompletionPort((HANDLE)sClient, CompletionPort, (DWORD)PerHandleData, 0); // 建立一个Overlapped，并使用这个Overlapped结构对socket投递操作 PerIoData = new PER_IO_OPERATION_DATA(); ZeroMemory(PerIoData, sizeof(PER_IO_OPERATION_DATA)); PerIoData->DataBuf.buf = PerIoData->Buffer; PerIoData->DataBuf.len = DATA_BUFSIZE; // 投递一个WSARecv操作 DWORD Flags = 0; DWORD dwRecv = 0; WSARecv(sClient, &PerIoData->DataBuf, 1, &dwRecv, &Flags, &PerIoData->Overlapped, NULL); } DWORD dwByteTrans; PostQueuedCompletionStatus(CompletionPort, dwByteTrans, 0, 0); closesocket(sListen);}