socket编程 -- epoll模型服务端/客户端通信的实现

心已赠人 2022-08-20 08:18 211阅读 0赞

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 1024
    
    int 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 1024
    
    int 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

![这里写图片描述][20160217144018592]

[20160217144018592]: /images/20220731/12b4e558c1e34047bcf2935af4ccc554.png