socket编程 -- epoll模型服务端/客户端通信的实现

https://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*/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;
}

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;
}

编译及执行

在终端1先执行：

yu@ubuntu:~/Linux/217/epoll$ ls
client.c  server.c
yu@ubuntu:~/Linux/217/epoll$ gcc -o client client.c
yu@ubuntu:~/Linux/217/epoll$ gcc -o server server.c
yu@ubuntu:~/Linux/217/epoll$ ./server

另开一终端2：

yu@ubuntu:~/Linux/217/epoll$ ./client
hey how are you
HEY HOW ARE YOU
bye
BYE

再另开一终端3：

yu@ubuntu:~/Linux/217/epoll$ ./client
i am here 007
I AM HERE 007
hehe
HEHE

最后开一终端4：

yu@ubuntu:~/Linux/217/epoll$ ./client
i am 008
I AM 008
zai jian
ZAI JIAN

关闭3个客户端(CTR+C)后服务端窗口：

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