网络编程(4)select函数实现I/O多路复用服务器

    我按理解整了个基于select模式的单进程多路复用并发服务器，并写了个简单的测试程序测了下，虽然离实用还差得远，但用来练习select够用了。

至于如何实现的细节，代码注释算比较清楚，就不多弄了。

一。服务器部份

单进程并发服务器代码:

/*************************************************Author: xiongchuanliangDescription: I/O复用(异步阻塞)模式_单进程+select模式服务器编译命令:Linux:g++ -g -o tcpserverasynselect2 tcpserverasynselect2.cpp -m64 -I./common./tcpserverasynselect2**************************************************/// 客户端代码#include <stdio.h>#include <stdlib.h>#include <string.h>#include "initsock.h"#include "common.h"#include <time.h>//客户端Socket信息结构体typedef struct _client_sock{        int    fd;//客户端socket描述符struct sockaddr_in addr;    //客户端地址信息结构体    time_t lastseconds;//可依这个计算空闲时间,空闲太长的连接可以关闭。} client_sock; CInitSock initSock;//#define IDLE_MAXTIME xxx  //最长空闲时长 DEMO忽略//#define SELECT_MAXWAITTIME xxxxx#define NET_TIMEOUT 5000  //发送超时时限 5sint main(int argc, char* argv[]){//fd_set 是通过bit位来存放文件描述符，可通过sizeof(fd_set) * 8 //来得可支持的最大文件描述符数,但受系统限制，基本达不到 fd_set readset;//select()函数 readset  int nSelectMaxfd = 0;//select() maxfdp参数 int nSelectRet = 0;//select() 返回值 //int nCheckTimeval = 5;//轮询间隔 SOCKET sListen,sClient,recvSockfd; client_sock arrClientSock[FD_SETSIZE]; //存放需要select()监控的fd.  int arrClientSockConnAmt = 0;//实际监控fd数  socklen_t nAddrlen = sizeof(struct sockaddr_in);  time_t tCurrSysTime; char recvData[MAXDATASIZE]={0}; int i = 0 ;//创建套接字sListen = socket(AF_INET,SOCK_STREAM,IPPROTO_TCP);if(sListen == INVALID_SOCKET){PrintError("socket() failed.\n");exit(EXIT_FAILURE);}//bind() 地址可立即重用int nResAddr = 1;setsockopt( sListen, SOL_SOCKET, SO_REUSEADDR, (const char*)&nResAddr, sizeof(nResAddr) );int nNetTimeout = NET_TIMEOUT;//设置发送超时时限setsockopt(sListen,SOL_SOCKET,SO_SNDTIMEO,(char *)&nNetTimeout,sizeof(int) );//设置接收超时时限setsockopt(sListen,SOL_SOCKET,SO_RCVTIMEO,(char *)&nNetTimeout,sizeof(int));//绑定本地IP和端口到套接字struct sockaddr_in server_addr;server_addr.sin_family = AF_INET;        server_addr.sin_port = htons(SERVPORT); //大于1024且小于65535server_addr.sin_addr.s_addr = INADDR_ANY;bzero(&(server_addr.sin_zero),8);if(bind(sListen,(struct sockaddr *)&server_addr,sizeof(struct sockaddr)) == SOCKET_ERROR)    {PrintError("bind() failed.");exit(EXIT_FAILURE);    }    //开始监听// listen(套接字,监听队列中允许保持的尚未处理的最大连接数量)// listen仅用在支持连接的套接字上，如SOCK_STREAM类型的套接字// 如果连接数超过BACKLOG，客户端将收到WSAECONNREFUSED错误    if(listen(sListen, BACKLOG) == SOCKET_ERROR) //FD_SETSIZE    {  PrintError("sListen() failed.");        exit(EXIT_FAILURE);    }//初始化for(int i=0;i<FD_SETSIZE;i++){arrClientSock[i].fd = -1;}    nSelectMaxfd = sListen; //设置select()函数maxfdp参数//循环接收数据while(true){struct sockaddr_in remoteAddr;tCurrSysTime = time(NULL); //系统当前时间//重建fd_set集合FD_ZERO(&readset); //每次循环须重新初始化,否则select不能检测描述符变化//将数组中的fd清理并赋给readsetarrClientSockConnAmt = 0;FD_SET(sListen,&readset); //将socket描述符加入检测集合 nSelectMaxfd = sListen;  //设置select()函数maxfdp参数for(i=0;i< FD_SETSIZE;i++){if(arrClientSock[i].fd > 0) //从描述符数组中找到一个还没用的保存进去{//对于空闲时间太长的,可能客户端已非常规的断开如断网，停电之类,将其关闭并从数组中删除,DEMO省略/*if( tCurrSysTime - arrClientSock[i].lastseconds  > IDLE_MAXTIME){close(arrClientSock[i].fd);arrClientSock[i].fd = -1;arrClientSock[i].lastseconds  = 0;memset(&arrClientSock[i].addr,0,sizeof(struct sockaddr_in));}else{*/FD_SET(arrClientSock[i].fd,&readset);arrClientSockConnAmt ++;//maxfdpif( arrClientSock[i].fd > nSelectMaxfd){nSelectMaxfd = arrClientSock[i].fd ;}//}} // end if > 0}//调用select//超时则返回0,否则返回发生事件的文件描述符的个数nSelectRet = select(nSelectMaxfd+1,&readset,NULL,NULL,NULL); //设置为阻塞状态//struct sockaddr_in remoteAddr;//struct timeval timeout={nCheckTimeval,0}; //阻塞式select, 超时时间. timeval{一个是秒数，另一个是毫秒数}//nSelectRet = select(nSelectMaxfd+1,&readset,NULL,NULL,&timeout); //设置select在超时时间内阻塞if( FD_ISSET(sListen,&readset) ){printf("select() 返回值 = %d. \n",nSelectRet );printf("accept() 连接客户端.\n");//调用accept,连接一个客户端sClient = accept(sListen,(struct sockaddr *)&remoteAddr,(socklen_t *)&nAddrlen);if( sClient <= 0) // == INVALID_SOCKET) //-1{PrintError("accept() failed.");continue;}//描述符数组已满if( arrClientSockConnAmt + 1 > FD_SETSIZE ){printf("ERROR: 等待连接的客户端太多!超出处理能力。\n");continue;}//将连接上的客户端放入数组，//后续可以再写个for，检查已正常close的并把空闲太长的close掉，//把arrClientSockConnAmt设为实际值,并注意设置nSelectMaxfd的值for(i=0;i< FD_SETSIZE;i++){if(arrClientSock[i].fd < 0) //从描述符数组中找到一个还没用的保存进去{arrClientSock[i].fd = sClient;arrClientSock[i].addr = remoteAddr;arrClientSock[i].lastseconds = time(NULL);printf("连接上的客户端IP = %s. \n",inet_ntoa(arrClientSock[i].addr.sin_addr) );arrClientSockConnAmt ++;//maxfdpif( sClient > nSelectMaxfd){nSelectMaxfd = sClient;}break;}}//如果select()检测到多个文件描述符并发时，则继续while,生成新的socket放入数组nSelectRet -= 1; if(nSelectRet <= 0){continue;//如果没有新客户端连接，则继续循环}} //end if( FD_ISSET(sListen,&readset) )//把select()函数返回的有发生事件的Socket描述符保存完后，统一在这做响应处理for(i = 0;i<arrClientSockConnAmt; i++){ //如果客户端描述符小于0,则没有连接 if( arrClientSock[i].fd < 0){continue;}recvSockfd = arrClientSock[i].fd;if( FD_ISSET(recvSockfd,&readset) ) //检查可读{//接收数据memset(recvData,0,sizeof(recvData)); //重新清空缓冲区printf("recv() fd[%d].\n",i);int recvbytes = recv(recvSockfd, recvData, MAXDATASIZE, 0);    if( recvbytes == 0){printf("recv() no data!\n");close(recvSockfd);FD_CLR(recvSockfd,&readset);arrClientSock[i].fd=-1;arrClientSockConnAmt --;printf("close() \n");}else if( recvbytes < 0){PrintError("recv() failed");close(recvSockfd);FD_CLR(recvSockfd,&readset);arrClientSock[i].fd=-1;arrClientSockConnAmt --;printf("close() \n");;//exit(EXIT_FAILURE); //刷屏}else if(recvbytes > 0){            recvData[recvbytes]='\0';printf("收到信息:%s\n",recvData);//发送数据到客户端char sendData[500] ={0};strcpy(sendData,"Hello client!\n");strcat(sendData,recvData);send(recvSockfd, sendData, strlen(sendData), 0);//更新一下fd最后响应时间arrClientSock[i].lastseconds = time(NULL);//如果没有新客户端连接，则break forif( (--nSelectRet) <= 0){break;}} //end if recv} //end if( FD_ISSET(recvSockfd,&readset) )} //end for} //end while(1)//关闭监听套接字close(sListen);exit(EXIT_SUCCESS);}

二。测试 部份

用于测试的代码：

/*************************************************Author: xiongchuanliangDescription: 通过在不同机器或会话窗口运行测试程序，生成多个线程连接Socket服务器来完成测试编译命令:Linux:g++ -o testthread2 testthread2.cpp -m64 -I./common -lpthread./testthread2**************************************************/// 客户端代码#include <stdio.h>#include <stdlib.h>#include <string.h>#include "initsock.h"#include "common.h"#include <pthread.h>#include <string.h>#include <sys/stat.h>//指定要连接的服务器ip#define SERVIP"127.0.0.1"  #define MAX_THREAD 50  //生成线程数CInitSock initSock;void *TestSocket(void *p); //连接服务器int main(int argc, char* argv[]){pthread_t tpid[MAX_THREAD];for(int i=0;i< MAX_THREAD - 1;i++){if( pthread_create(&tpid[i],NULL,&TestSocket,&i) != 0 )  { fprintf(stderr,"Create Thread[%d] Error:%s\n",i,strerror(errno)); exit(EXIT_FAILURE); } //pthread_join(tpid[i],NULL);}sleep(10);exit(EXIT_SUCCESS);}void *TestSocket(void *p){int ti = *((int *)p);pid_t pid;pid = getpid();pthread_t tid;tid = pthread_self();time_t ttm = time(NULL); char testMsg[100] = {0}; snprintf(testMsg,100,"thread id=%lu pid=%u ttm=%d \n",tid, (unsigned int)pid,ttm); //建立套接字SOCKET sclient = socket(AF_INET,SOCK_STREAM,IPPROTO_TCP);if(sclient == INVALID_SOCKET){PrintError("invalid() failed");exit(EXIT_FAILURE);}//指定要连接的服务器地址和端口struct sockaddr_in server_addr;server_addr.sin_family = AF_INET;server_addr.sin_port = htons(SERVPORT);server_addr.sin_addr.s_addr =inet_addr(SERVIP);memset(&(server_addr.sin_zero),0,8);//将套接字连接上服务器if( connect(sclient,(struct sockaddr *)&server_addr,sizeof(struct sockaddr) ) == SOCKET_ERROR){PrintError("connect() failed");exit(EXIT_FAILURE);}//发送数据到服务端send(sclient,testMsg,strlen(testMsg),0);//接收返回的数据char recvData[MAXDATASIZE] = {0};int recvbytes = recv(sclient,recvData,MAXDATASIZE,0);if( recvbytes == 0){printf("thread id=%lu recv() no data!\n",tid);}else if( recvbytes < 0){PrintError("recv() failed");exit(EXIT_FAILURE);}else if( recvbytes > 0){recvData[recvbytes]='\0';printf("thread id=%lu tm=%d \n服务端返回信息:%s\n",tid,time(NULL),recvData);}close(sclient);return NULL;}

测试效果图:

代码中写到的头文件请看： 网络编程(1)跨平台的Socket同步阻塞工作模式例子

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