socket编程 -- epoll模型服务端/客户端通信的实现

转载：http://blog.csdn.net/y396397735/article/details/50680359

本例实现如下功能： 
支持多客户端与一个服务端进行通信，客户端给服务端发送字符串数据，服务端将字符串中小写转为大写后发送回客户端，客户端打印输出经转换后的字符串。 
例如：发送abcde，打印输出ABCDE 
服务端源码如下：

/*server.c*/#include <stdio.h>#include <stdlib.h>#include <string.h>#include <netinet/in.h>#include <arpa/inet.h>#include <sys/epoll.h>#include <errno.h>#define BUFSIZE 666#define SERV_PORT 8000#define OPEN_MAX 1024int main(){    int i, j, maxi, listenfd, connfd, sockfd;    int nready, efd, res;    ssize_t n;    char buf[BUFSIZE], str[INET_ADDRSTRLEN];    socklen_t clilen;    int client[OPEN_MAX];    struct sockaddr_in cliaddr, servaddr;    struct epoll_event tep, ep[OPEN_MAX];//监听事件    /*分配一个网络通信套接字，监听文件描述符listenfd*/    listenfd = socket(AF_INET, SOCK_STREAM, 0);    /*初始化 IP类型 端口*/    bzero(&servaddr, sizeof(servaddr));    servaddr.sin_family = AF_INET;    servaddr.sin_addr.s_addr = htonl(INADDR_ANY);    servaddr.sin_port = htons(SERV_PORT);    /*将listenfd绑定服务端地址*/    bind(listenfd, (struct sockaddr*)&servaddr, sizeof(servaddr));    /*监听请求*/    listen(listenfd, 20);    /*将客户端标识初始化为-1*/    for(i = 0; i < OPEN_MAX; i++){        client[i] = -1;    }    maxi = -1;    /*告诉内核要监听的文件描述符个数 OPEN_MAX = 1024，该 函数生成一个epoll专用的文件描述符。它其实是在内核申请一空间，用来存放你想关注的socket fd上是否发生以及发生了什么事件。size就是你在这个epoll fd上能关注的最大socket fd数。随你定好了。只要你有空间*/    efd = epoll_create(OPEN_MAX);    if(efd == -1){        perror("epoll_create");    }    tep.events = EPOLLIN;/*监听文件描述符的可读事件*/    tep.data.fd = listenfd;/*设置为监听的文件描述符*/    /*控制epoll监控的文件描述符上的事件*/    res = epoll_ctl(efd, EPOLL_CTL_ADD/*注册新的fd到efd*/, listenfd, &tep);    if(res == -1)        perror("epoll_ctl");    for(;;){        /*等待所监控文件描述符上有事件的产生，阻塞监听*/        nready = epoll_wait(efd, ep, OPEN_MAX, -1);        if(nready == -1)            perror("epoll_wait");        for(i = 0; i < nready; i++){            if(!(ep[i].events & EPOLLIN))/*若不是EPOLLIN事件，不做往下的处理*/                continue;            if(ep[i].data.fd == listenfd){ /*若是EPOLLIN，执行连接，接受请求*/                clilen = sizeof(cliaddr);                /*接受请求，分配新文件描述符connfd进行通信*/                connfd = accept(listenfd, (struct sockaddr*)&cliaddr, &clilen);                printf("received from %s at PORT %d\n", (char*)inet_ntop(AF_INET, &cliaddr.sin_addr, str, sizeof(str)), ntohs(cliaddr.sin_port));                /*若将此新客户端添加至客户端集中*/                for(j = 0; j < OPEN_MAX; j++)                    if(client[j] < 0){                        client[j] = connfd;                        break;                    }                if(j == OPEN_MAX)                    perror("客户端超过限制");                if(j > maxi)                    maxi = j;//保证maxi为最大文件描述符                tep.events = EPOLLIN;                tep.data.fd = connfd;                res = epoll_ctl(efd, EPOLL_CTL_ADD/*注册新的connfd到efd*/, connfd, &tep);                if(res == -1)                    perror("epoll_ctl");            }else{/*处理efd中监听的客户端请求*/                sockfd = ep[i].data.fd;                n = read(sockfd, buf, BUFSIZE);                if(n == 0){ /*读取若为空*/                    for(j = 0; j <= maxi; j++){                        if(client[j] == sockfd){                            client[j] = -1;                            break;                        }                    }                    /*清除对sockfd文件描述符事件的监听*/                    res = epoll_ctl(efd, EPOLL_CTL_DEL, sockfd, NULL);                    if(res == -1)                        perror("epoll_ctl");                    close(sockfd);                    printf("client[%d] closed connection\n", j);                }else{/*非空则处理客户端信息*/                    for(j = 0; j<n; j++)                        buf[j] = toupper(buf[j]);                    /*写入与客户端通信的文件描述符sockfd*/                    write(sockfd, buf, n);                }            }        }    }    /*关闭监听*/    close(listenfd);    close(efd);    return 0;}
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客户端源码如下：

/*client.c*/#include <stdio.h>#include <stdlib.h>#include <string.h>#include <unistd.h>#include <netinet/in.h>#include <arpa/inet.h>#include <sys/epoll.h>#include <errno.h>#define BUFSIZE 666#define SERV_PORT 8000#define OPEN_MAX 1024int main(int argc, char *argv[]){    struct sockaddr_in servaddr;    char buf[BUFSIZE];    int sockfd, n;    sockfd = socket(AF_INET, SOCK_STREAM, 0);    bzero(&servaddr, sizeof(servaddr));    servaddr.sin_family = AF_INET;    inet_pton(AF_INET, "127.0.0.1", &servaddr.sin_addr);    servaddr.sin_port = htons(SERV_PORT);    /*连接服务端*/    connect(sockfd, (struct sockaddr*)&servaddr, sizeof(servaddr));    while(fgets(buf, BUFSIZE, stdin) != NULL){        /*通过sockfd给服务端发送数据*/        write(sockfd, buf, strlen(buf));        n = read(sockfd, buf, BUFSIZE);        if(n == 0)            printf("the other side has been closed.\n");        else/*打印输出服务端传过来的数据*/            write(STDOUT_FILENO, buf, n);    }    close(sockfd);    return 0;}
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编译及执行

在终端1先执行：

yu@ubuntu:~/Linux/217/epoll$ lsclient.c  server.cyu@ubuntu:~/Linux/217/epoll$ gcc -o client client.cyu@ubuntu:~/Linux/217/epoll$ gcc -o server server.cyu@ubuntu:~/Linux/217/epoll$ ./server
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另开一终端2：

yu@ubuntu:~/Linux/217/epoll$ ./clienthey how are youHEY HOW ARE YOUbyeBYE
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再另开一终端3：

yu@ubuntu:~/Linux/217/epoll$ ./clienti am here 007I AM HERE 007heheHEHE
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最后开一终端4：

yu@ubuntu:~/Linux/217/epoll$ ./clienti am 008I AM 008zai jianZAI JIAN
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关闭3个客户端(CTR+C)后服务端窗口：

yu@ubuntu:~/Linux/217/epoll$ ./serverreceived from 127.0.0.1 at PORT 58385received from 127.0.0.1 at PORT 58386received from 127.0.0.1 at PORT 58387client[2] closed connectionclient[1] closed connectionclient[0] closed connection