select模型使用例子

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

#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;
}

#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

// 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);
                }
            }
        }
    }
}

// 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。