Socket I/O模型之事件选择(WSAEventSelect)

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：

C++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--;

}

// writeby larry

//2009-8-20

// Thisis a server using WSAEventSelect model.

#include"stdafx.h"

#include<WINSOCK2.H>

#include<stdio.h>

#pragmacomment(lib, "ws2_32.lib")

#definePORT 5150

#defineMSGSIZE 1024

intg_iTotalConn = 0;

SOCKETg_CliSocketArr[MAXIMUM_WAIT_OBJECTS];

WSAEVENTg_CliEventArr[MAXIMUM_WAIT_OBJECTS];

DWORDWINAPI WorkerThread(LPVOID lpParam);

voidCleanup(int index);

intmain(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("Acceptedclient:%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;

}

DWORDWINAPI 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;

}

voidCleanup(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--;

}

事件选择模型也比较简单，实现起来也不是太复杂，它的基本思想是将每个套接字都和一个WSAEVENT对象对应起来，并且在关联的时候指定需要关注的哪些网络事件。一旦在某个套接字上发生了我们关注的事件（FD_READ和FD_CLOSE），与之相关联的WSAEVENT对象被Signaled。程序定义了两个全局数组，一个套接字数组，一个WSAEVENT对象数组，其大小都是MAXIMUM_WAIT_OBJECTS（64），两个数组中的元素一一对应。

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%。