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WSAEventSelect和WSAAsyncSelect模型类似,它也允许应用程序在一个或多个套接字上,接收以事件为基础的网络事件通知。对于WSAAsyncSelect模型采用的网络事件来说,它们均可原封不动地移植到事件选择模型上。在用事件选择模型开发的应用程序中,也能接收和处理所有那些事件。该模型最主要的差别在于网络事件会投递至一个事件对象句柄,而非投递至一个窗口例程。
服务器端代码:
// write by larry
// 2009-8-20
// This is a server using WSAEventSelect model.
#include "stdafx.h"
#include <WINSOCK2.H>
#include <stdio.h>
#pragma comment(lib, "ws2_32.lib")
#define PORT 5150
#define MSGSIZE 1024
int g_iTotalConn = 0;
SOCKET g_CliSocketArr[MAXIMUM_WAIT_OBJECTS];
WSAEVENT g_CliEventArr[MAXIMUM_WAIT_OBJECTS];
DWORD WINAPI WorkerThread(LPVOID lpParam);
void Cleanup(int index);
int main(int argc, char* argv[])
{
WSADATA wsaData;
SOCKET sListen, sClient;
SOCKADDR_IN local, client;
DWORD dwThreadId;
int iAddrSize = sizeof(SOCKADDR_IN);
// Initialize windows socket library
WSAStartup(0x0202, &wsaData);
// Create listening socket
sListen = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
// Bind
local.sin_family = AF_INET;
local.sin_addr.S_un.S_addr = htonl(INADDR_ANY);
local.sin_port = htons(PORT);
bind(sListen, (sockaddr*)&local, sizeof(SOCKADDR_IN));
// Listen
listen(sListen, 3);
// Create worker thread
CreateThread(NULL, 0, WorkerThread, NULL, 0, &dwThreadId);
while (TRUE)
{
// Accept a connection
sClient = accept(sListen, (sockaddr*)&client, &iAddrSize);
printf("Accepted client:%s:%d\n", inet_ntoa(client.sin_addr), ntohs(client.sin_port));
// Associate socket with network event
g_CliSocketArr[g_iTotalConn] = sClient;
g_CliEventArr[g_iTotalConn] = WSACreateEvent();
WSAEventSelect(g_CliSocketArr[g_iTotalConn], g_CliEventArr[g_iTotalConn], FD_READ|FD_CLOSE);
g_iTotalConn++;
}
return 0;
}
DWORD WINAPI WorkerThread(LPVOID lpParam)
{
int ret, index;
WSANETWORKEVENTS NetworkEvents;
char szMessage[MSGSIZE];
while (TRUE)
{
ret = WSAWaitForMultipleEvents(g_iTotalConn, g_CliEventArr, FALSE, 1000, FALSE);
if (ret == WSA_WAIT_FAILED || ret == WSA_WAIT_TIMEOUT)
{
continue;
}
index = ret - WSA_WAIT_EVENT_0;
WSAEnumNetworkEvents(g_CliSocketArr[index], g_CliEventArr[index], &NetworkEvents);
if (NetworkEvents.lNetworkEvents & FD_READ)
{
// Receive message from client
ret = recv(g_CliSocketArr[index], szMessage, MSGSIZE, 0);
if (ret == 0 || (ret == SOCKET_ERROR && WSAGetLastError() == WSAECONNRESET))
{
Cleanup(index);
}
else
{
szMessage[ret] = '\0';
send(g_CliSocketArr[index], szMessage, strlen(szMessage), 0);
}
}
if (NetworkEvents.lNetworkEvents & FD_CLOSE)
{
Cleanup(index);
}
}
return 0;
}
void Cleanup(int index)
{
closesocket(g_CliSocketArr[index]);
WSACloseEvent(g_CliEventArr[index]);
if (index < g_iTotalConn-1)
{
g_CliSocketArr[index] = g_CliSocketArr[g_iTotalConn-1];
g_CliEventArr[index] = g_CliEventArr[g_iTotalConn-1];
}
g_iTotalConn--;
}
同样的,这里的程序没有考虑两个问题,一是不能无条件的调用accept,因为我们支持的并发连接数有限。解决方法是将套接字按 MAXIMUM_WAIT_OBJECTS分组,每MAXIMUM_WAIT_OBJECTS个套接字一组,每一组分配一个工作者线程;或者采用 WSAAccept代替accept,并回调自己定义的Condition Function。第二个问题是没有对连接数为0的情形做特殊处理,程序在连接数为0的时候CPU占用率为100%。