Linux下socket通信和epoll

上一篇博客用多线程实现服务端和多个客户端的通信，但是在实际应用中如果服务端有高并发的需求，多线程并不是一个好选择。

实现高并发的一种方法是IO多路复用，也就是select，poll，epoll等等。

于是我采用epoll再修改了服务端，实现单线程服务多个客户端。

服务端：

 #include <stdio.h>
 #include <stdlib.h>
 #include <fcntl.h> // open function
 #include <unistd.h> // close function
 #include <sys/socket.h>
 #include <netinet/in.h>
 #include <string.h>
 #include <pthread.h>
 #include <errno.h>
 #include <sys/epoll.h>
 
 const int PORT = ;
 /*
     listen_loop(): epoll监听套接字，作不同处理
     accept_conn(): 新的客户端连接进来，执行accept，将fd加入epoll set
     recv_message(): recv并且重复输出一份给客户端
  */
 void listen_loop();
 void accept_conn(unsigned int sock_fd, unsigned int epollfd);
 void recv_message(unsigned int sock_fd);
 
 int main(void) {
     int sock_fd;
     struct sockaddr_in server_addr;
 
     //初始化socket
     sock_fd = socket(AF_INET, SOCK_STREAM, );
     if (sock_fd < ) {
         perror("socket:");
         return ;
     }
 
     //编辑地址
     memset(&server_addr, , sizeof(server_addr));
     server_addr.sin_family = AF_INET;//ipv_4
     server_addr.sin_port = htons(PORT);//监听端口8888
     server_addr.sin_addr.s_addr = INADDR_ANY;//本地的任意地址
 
     //绑定然后监听
     if (bind(sock_fd, (struct sockaddr*)&server_addr, sizeof(server_addr)) < ) {
         perror("bind:");
         return ;
     }
     if (listen(sock_fd, ) < ) {
         perror("listen");
         return ;
     }
 
     listen_loop(sock_fd);
 
     return ;
 }
 void accept_conn(unsigned int sock_fd, unsigned int epollfd) {
     struct sockaddr_in clientaddr;
     struct epoll_event event;
     socklen_t len = sizeof(struct sockaddr);
     int accept_fd = ;
 
     accept_fd = accept(sock_fd, (struct sockaddr*)&clientaddr, &len);
 
     if (accept_fd <= ) {
         perror("accept error");
         return;
     }
 
     //将新建连接加入epoll set
     event.data.fd = accept_fd;
     event.events = EPOLLIN | EPOLLET | EPOLLRDHUP;
     epoll_ctl(epollfd, EPOLL_CTL_ADD, accept_fd, &event);
     return;
 }
 
 void recv_message(unsigned int sock_fd) {
     char recv_buf[], send_buf[];
 
     memset(recv_buf, , sizeof(recv_buf));
     memset(send_buf, , sizeof(send_buf));
 
     recv(sock_fd, recv_buf, sizeof(recv_buf), );
     fputs(recv_buf, stdout);
     strcpy(send_buf, recv_buf);
     send(sock_fd, send_buf, sizeof(send_buf), );
 
     return;
 }
 void listen_loop(unsigned int sock_fd)
 {
     int epollfd, i, ret;
     int timeout = ;
     struct epoll_event event;
     struct epoll_event eventList[];
 
     /*创建epoll监听事件*/
     epollfd = epoll_create();
     event.events = EPOLLIN | EPOLLET;
     event.data.fd = sock_fd;
 
     /*注册epoll监听事件.*/
     if (epoll_ctl(epollfd, EPOLL_CTL_ADD, sock_fd, &event) < ) {
         printf("register epoll event err !");
         return;
     }
 
     while () {
         ret = epoll_wait(epollfd, eventList, , timeout);
 
         /*epoll事件错误.*/
         if (ret < ) {
             printf("epoll event err!");
             break;
         }
         /*无事件返回.*/
         else if (ret == ) {
             continue;
         }
 
         /*epoll返回事件.*/
         for (i = ; i < ret; i++) {
             /*epoll 错误*/
             if ((eventList[i].events & EPOLLERR) || (eventList[i].events & EPOLLHUP) || !(eventList[i].events & EPOLLIN)) {
                 printf("epoll error\n");
                 close(eventList[i].data.fd);
                 exit(-);
             }
 
             //half connection
             if (eventList[i].events & EPOLLRDHUP) {
                 printf("//one client close the conne.//\n");
                 close(eventList[i].data.fd);
             }
 
             /*accept事件*/
             if (eventList[i].data.fd == sock_fd) {
                 accept_conn(sock_fd, epollfd);
             }
             /*非sock_fd则为其他事件.*/
             else {
                 recv_message(eventList[i].data.fd);
             }
         }
     }
     close(epollfd);
     close(sock_fd);
     return;
 }