【网络编程】之十一、重叠IO Overlapped IO 完成例程
完成例程是Win Sockets提供的另一种管理完成的重叠I/O方法，完成例程是一个函数，当发起重叠操作时，将该函数传递给发起操作的函数，当重叠IO操作完成时由系统调用。
下面来看一下例程必须拥有下面的函数原型：
下面来看一下WSAOVERLAPPED结构：
#include <winsock2.h>#include <ws2tcpip.h>#include <stdio.h>#include <stdlib.h>// Need to link with Ws2_32.lib#pragma comment(lib, "ws2_32.lib")int __cdecl main(){ //--------------------------------------------- // Declare and initialize variables WSADATA wsaData; WSABUF DataBuf; WSAOVERLAPPED Overlapped; SOCKET SendToSocket = INVALID_SOCKET; struct sockaddr_in RecvAddr; struct sockaddr_in LocalAddr; int RecvAddrSize = sizeof (RecvAddr); int LocalAddrSize = sizeof (LocalAddr); u_short Port = 27015; struct hostent *localHost; char *ip; char SendBuf[1024] = "Data buffer to send"; int BufLen = 1024; DWORD BytesSent = 0; DWORD Flags = 0; int rc, err; int retval = 0; //--------------------------------------------- // Initialize Winsock // Load Winsock rc = WSAStartup(MAKEWORD(2, 2), &wsaData); if (rc != 0) { printf("Unable to load Winsock: %d\n", rc); return 1; } // Make sure the SendOverlapped struct is zeroed out SecureZeroMemory((PVOID)&Overlapped, sizeof(WSAOVERLAPPED)); // Create an event handle and setup the overlapped structure. Overlapped.hEvent = WSACreateEvent(); if (Overlapped.hEvent == NULL) { printf("WSACreateEvent failed with error: %d\n", WSAGetLastError()); WSACleanup(); return 1; } //--------------------------------------------- // Create a socket for sending data SendToSocket = WSASocket(AF_INET, SOCK_DGRAM, IPPROTO_UDP, NULL, 0, WSA_FLAG_OVERLAPPED); if (SendToSocket == INVALID_SOCKET) { printf("socket failed with error: %d\n", WSAGetLastError()); WSACloseEvent(Overlapped.hEvent); WSACleanup(); return 1; } //--------------------------------------------- // Set up the RecvAddr structure with the IP address of // the receiver (in this example case "127.0.0.1") // and the specified port number. RecvAddr.sin_family = AF_INET; RecvAddr.sin_port = htons(Port); RecvAddr.sin_addr.s_addr = inet_addr("127.0.0.1"); //--------------------------------------------- // Set up the LocalAddr structure with the local IP address // and the specified port number. localHost = gethostbyname("");//返回本地主机的标准主机名 ip = inet_ntoa(*(struct in_addr *) *localHost->h_addr_list); LocalAddr.sin_family = AF_INET; LocalAddr.sin_addr.s_addr = inet_addr(ip); LocalAddr.sin_port = htons(Port); //--------------------------------------------- // Bind the sending socket to the LocalAddr structure // that has the internet address family, local IP address // and specified port number. rc = bind(SendToSocket, (struct sockaddr *) &LocalAddr, LocalAddrSize); if (rc == SOCKET_ERROR) { printf("bind failed with error: %d\n", WSAGetLastError()); WSACloseEvent(Overlapped.hEvent); closesocket(SendToSocket); WSACleanup(); return 1; } //--------------------------------------------- // Send a datagram to the receiver printf("Sending a datagram...\n"); DataBuf.len = BufLen; DataBuf.buf = SendBuf; rc = WSASendTo(SendToSocket, &DataBuf, 1, &BytesSent, Flags, (SOCKADDR *) & RecvAddr, RecvAddrSize, &Overlapped, NULL); if ((rc == SOCKET_ERROR) && (WSA_IO_PENDING != (err = WSAGetLastError()))) { printf("WSASendTo failed with error: %d\n", err); WSACloseEvent(Overlapped.hEvent); closesocket(SendToSocket); WSACleanup(); return 1; } rc = WSAWaitForMultipleEvents(1, &Overlapped.hEvent, TRUE, INFINITE, TRUE); if (rc == WSA_WAIT_FAILED) { printf("WSAWaitForMultipleEvents failed with error: %d\n", WSAGetLastError()); retval = 1; } rc = WSAGetOverlappedResult(SendToSocket, &Overlapped, &BytesSent, FALSE, &Flags);//返回指定套接字口上一个重叠操作结果。 if (rc == FALSE) { printf("WSASendTo failed with error: %d\n", WSAGetLastError()); retval = 1; } //--------------------------------------------- // When the application is finished sending, close the socket. printf("Finished sending. Closing socket.\n"); WSACloseEvent(Overlapped.hEvent); closesocket(SendToSocket); printf("Exiting.\n"); //--------------------------------------------- // Clean up and quit. WSACleanup(); return (retval);}
WSAOVERLAPPED 和 WSAGetOverlappedResult在上一节中都给出过：http://blog.csdn.net/jofranks/article/details/7895316
----2012/9/20
----jofranks 于南昌
