Socket I/O模型之选择(select)（转）

http://tangfeng.iteye.com/blog/518135

在windows平台构建网络应用，必须了解socket I/O模型。windows提供了选择(select)、异步选择(WSAAsyncSelect)、事件选择(WSAEventSelect)、重叠I /O(overlapped I/O)和完成端口(completion port)。

一、客户端代码

C++代码



#include "stdafx.h"

#include <WINSOCK2.H>

#include <stdio.h>

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

#define SERVER_ADDRESS "192.168.10.56"

#define PORT 5150

#define MSGSIZE 1024

int main(int argc, char* argv[])

{

WSADATA wsaData;

SOCKET sClient;

SOCKADDR_IN server;

char szMessage[MSGSIZE];

int ret;

// Initialize windows socket library

WSAStartup(0x0202, &wsaData);

// Create client socket

sClient = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);

// Connect to server

memset(&server, 0, sizeof(SOCKADDR_IN));

server.sin_family = AF_INET;

server.sin_addr.S_un.S_addr = inet_addr(SERVER_ADDRESS);

server.sin_port = htons(PORT);

connect(sClient, (sockaddr*)&server, sizeof(SOCKADDR_IN));

while (TRUE)

{

printf("Send:");

gets(szMessage);

// Send message

send(sClient, szMessage, strlen(szMessage), 0);

// Receive message

ret = recv(sClient, szMessage, MSGSIZE, 0);

szMessage[ret] = '\0';

printf("Received [%d bytes]: '%s'\n", ret, szMessage);

}

// Clean up

closesocket(sClient);

WSACleanup();

return 0;

}

这是一个最简单的客户端代码，负责发送数据，然后接受返回。

二、使用select模型的服务器

C++代码



// write by larry

// 2009-8-20

// This is server using select model.

#include "stdafx.h"

#include <winsock.h>

#include <stdio.h>

#define PORT 5150

#define MSGSIZE 1024

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

int g_iTotalConn = 0;

SOCKET g_CliSocketArr[FD_SETSIZE];

DWORD WINAPI WorkerThread(LPVOID lpParam);

int main(int argc, char* argv[])

{

WSADATA wsaData;

SOCKET sListen, sClient;

SOCKADDR_IN local, client;

int iAddrSize = sizeof(SOCKADDR_IN);

DWORD dwThreadId;

// 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));

// Add socket to g_CliSocketArr

g_CliSocketArr[g_iTotalConn++] = sClient;

}

return 0;

}

DWORD WINAPI WorkerThread(LPVOID lpParam)

{

int i;

fd_set fdread;

int ret;

struct timeval tv = {1, 0};

char szMessage[MSGSIZE];

while (TRUE)

{

FD_ZERO(&fdread);

for (i = 0; i < g_iTotalConn; i++)

{

FD_SET(g_CliSocketArr[i], &fdread);

}

// We only care read event

ret = select(0, &fdread, NULL, NULL, &tv);

if (ret == 0)

{

// Time expired

continue;

}

for (i = 0; i < g_iTotalConn; i++)

{

if (FD_ISSET(g_CliSocketArr[i], &fdread))

{

// A read event happened on g_CliSocketArr

ret = recv(g_CliSocketArr[i], szMessage, MSGSIZE, 0);

if (ret == 0 || (ret == SOCKET_ERROR && WSAGetLastError() == WSAECONNRESET))

{

// Client socket closed

printf("Client socket %d closed.\n", g_CliSocketArr[i]);

closesocket(g_CliSocketArr[i]);

if (i < g_iTotalConn-1)

{

g_CliSocketArr[i--] = g_CliSocketArr[--g_iTotalConn];

}

}

else

{

// We reveived a message from client

szMessage[ret] = '\0';

send(g_CliSocketArr[i], szMessage, strlen(szMessage), 0);

}

}

}

}

}

这是异步模型中最简单的一种，服务器端的几个主要流程如下：

1.创建监听套接字，绑定，监听；
2.创建工作者线程；
3.创建一个套接字数组，用来存放当前所有活动的客户端套接字，每accept一个连接就更新一次数组；
4.接受客户端的连接。