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Linux网络编程——tcp并发服务器（I/O复用之select
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http://blog.csdn.net/lianghe_work/article/details/46519633
與多線程、多進(jìn)程相比，I/O復(fù)用最大的優(yōu)勢(shì)是系統(tǒng)開(kāi)銷小，系統(tǒng)不需要建立新的進(jìn)程或者線程，也不必維護(hù)這些線程和進(jìn)程。
代碼示例：
[csharp]?view plain
?copy #include?<stdio.h>??? #include?<unistd.h>?? #include?<stdlib.h>?? #include?<errno.h>?? #include?<string.h>?? #include?<sys/socket.h>?? #include?<sys/types.h>?? #include?<netinet/in.h>?? #include?<arpa/inet.h>?? #include?<sys/select.h>?? ? #define?SERV_PORT?8080?? #define?LIST?20????????????????//服務(wù)器最大接受連接?? #define?MAX_FD?10??????????????//FD_SET支持描述符數(shù)量?? ?? ?? int?main(int?argc,?char?*argv[])?? {?? ????int?sockfd;?? ????int?err;?? ????int?i;?? ????int?connfd;?? ????int?fd_all[MAX_FD];??? ?????? ?????? ????fd_set?fd_read;?????? ????fd_set?fd_select;???? ?? ????struct?timeval?timeout;??????????? ????struct?timeval?timeout_select;???? ?????? ????struct?sockaddr_in?serv_addr;????? ????struct?sockaddr_in?cli_addr;?????? ????socklen_t?serv_len;?? ????socklen_t?cli_len;?? ?????? ?????? ????timeout.tv_sec?=?10;?? ????timeout.tv_usec?=?0;?? ?????? ?????? ????sockfd?=?socket(AF_INET,?SOCK_STREAM,?0);?? ????if(sockfd?<?0)?? ????{?? ????????perror("fail?to?socket");?? ????????exit(1);?? ????}?? ?????? ?????? ????memset(&serv_addr,?0,?sizeof(serv_addr));?? ????serv_addr.sin_family?=?AF_INET;??????????? ????serv_addr.sin_port?=?htons(SERV_PORT);???? ????serv_addr.sin_addr.s_addr?=?htonl(INADDR_ANY);??? ?? ????serv_len?=?sizeof(serv_addr);?? ?????? ?????? ????err?=?bind(sockfd,?(struct?sockaddr?*)&serv_addr,?serv_len);?? ????if(err?<?0)?? ????{?? ????????perror("fail?to?bind");?? ????????exit(1);?? ????}?? ?? ?????? ????err?=?listen(sockfd,?LIST);?? ????if(err?<?0)?? ????{?? ????????perror("fail?to?listen");?? ????????exit(1);?? ????}?? ?????? ?????? ????memset(fd_all,?-1,?sizeof(fd_all));?? ?? ????fd_all[0]?=?sockfd;????? ?????? ????FD_ZERO(&fd_read);???? ????FD_SET(sockfd,?&fd_read);???? ?? ????int?maxfd?=?fd_all[0];???? ?????? ????while(1){?? ?????? ?????????? ????????fd_select?=?fd_read;?? ????????timeout_select?=?timeout;?? ?????????? ?????????? ?????????? ????????err?=?select(maxfd+1,?&fd_select,?NULL,?NULL,?NULL);?? ?????????? ????????if(err?<?0)?? ????????{?? ????????????????perror("fail?to?select");?? ????????????????exit(1);?? ????????}?? ?? ????????if(err?==?0){?? ????????????printf("timeout\n");?? ????????}?? ?????????? ?????????? ????????if(?FD_ISSET(sockfd,?&fd_select)?){?? ?????????????? ????????????cli_len?=?sizeof(cli_addr);?? ?????????????? ?????????????? ????????????connfd?=?accept(sockfd,?(struct?sockaddr?*)&cli_addr,?&cli_len);?? ????????????if(connfd?<?0)?? ????????????{?? ????????????????perror("fail?to?accept");?? ????????????????exit(1);?? ????????????}?? ?????????????? ?????????????? ????????????char?cli_ip[INET_ADDRSTRLEN]?=?{0};?? ????????????inet_ntop(AF_INET,?&cli_addr.sin_addr,?cli_ip,?INET_ADDRSTRLEN);?? ????????????printf("----------------------------------------------\n");?? ????????????printf("client?ip=%s,port=%d\n",?cli_ip,ntohs(cli_addr.sin_port));?? ?????????????? ?????????????? ????????????for(i=0;?i?<?MAX_FD;?i++){?? ????????????????if(fd_all[i]?!=?-1){?? ????????????????????continue;?? ????????????????}else{?? ????????????????????fd_all[i]?=?connfd;?? ????????????????????printf("client?fd_all[%d]?join\n",?i);?? ????????????????????break;?? ????????????????}?? ????????????}?? ?????????????? ????????????FD_SET(connfd,?&fd_read);?? ?????????????? ????????????if(maxfd?<?connfd)?? ????????????{?? ????????????????maxfd?=?connfd;???? ????????????}?? ?????????? ????????}?? ?????????? ?????????? ????????for(i=1;?i?<?maxfd;?i++){?? ????????????if(FD_ISSET(fd_all[i],?&fd_select)){?? ????????????????printf("fd_all[%d]?is?ok\n",?i);?? ?????????????????? ????????????????char?buf[1024]={0};???? ????????????????int?num?=?read(fd_all[i],?buf,?1024);?? ????????????????if(num?>?0){?? ?? ?????????????????????? ????????????????????printf("receive?buf?from?client?fd_all[%d]?is:?%s\n",?i,?buf);?? ?????????????????????? ?????????????????????? ????????????????????num?=?write(fd_all[i],?buf,?num);?? ????????????????????if(num?<?0){?? ????????????????????????perror("fail?to?write?");?? ????????????????????????exit(1);?? ????????????????????}else{?? ?????????????????????????? ????????????????????}?? ?????????????????????? ????????????????}?? ????????????????else?if(0?==?num){??? ?????????????????????? ?????????????????????? ????????????????????printf("client:fd_all[%d]?exit\n",?i);?? ????????????????????FD_CLR(fd_all[i],?&fd_read);?? ????????????????????close(fd_all[i]);?? ????????????????????fd_all[i]?=?-1;?? ?????????????????????? ????????????????????continue;?? ????????????????}?? ?????????????????? ????????????}else?{?? ?????????????????? ????????????}?? ????????}?? ????}?? ?????? ????return?0;?? }??
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