epoll 实现服务器详解-优快云博客

本文介绍了使用 epoll 创建和管理的服务器实现，包括 socket、bind、listen、accept 等步骤，以及 epoll_ctl 的 EPOLL_CTL_ADD 和 EPOLL_CTL_MOD 操作。服务器监听 6610 端口，并通过 epoll_wait 进行事件循环处理，实现连接接受和数据读写。

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下面这段代码来自：https://blog.youkuaiyun.com/LEOdabao/article/details/80339574

/*
*使用epoll实现的服务器
*/

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <time.h>
#include <string.h>
#include <poll.h>
#include <sys/epoll.h>
#include <limits.h>
#include <errno.h>

#define MAXLINE 1024
#define OPEN_MAX 128
#define INFTIM -1

char buf[MAXLINE];

int main(int argc, char **argv)
{
   int i, listenfd, connfd, sockfd, epollfd, nfds;
   int nready;
   ssize_t n;

   socklen_t clilen;
   struct pollfd client[OPEN_MAX];
   struct sockaddr_in cliaddr, serveraddr;
   struct epoll_event ev, events[20];//events是结构体数组，可以存放多个事件

   listenfd = socket(AF_INET, SOCK_STREAM, 0);
   bzero(&serveraddr,sizeof(serveraddr));

   serveraddr.sin_family = AF_INET;
   serveraddr.sin_addr.s_addr = htonl(INADDR_ANY);
   serveraddr.sin_port = htons(6610);

   epollfd = epoll_create1(0);
   ev.data.fd = listenfd;
   ev.events = EPOLLIN|EPOLLET;
   epoll_ctl(epollfd, EPOLL_CTL_ADD, listenfd, &ev);
   bind(listenfd, (struct sockaddr*)&serveraddr, sizeof(serveraddr));
   listen(listenfd,100);

   printf("ready for event loop\n");
   for(;;)
   {
       nfds = epoll_wait(epollfd, events, 20, -1);
       for(i = 0;i < nfds; ++i)
       {
           if(events[i].data.fd == listenfd)
           {
               clilen = sizeof(cliaddr);
               connfd = accept(listenfd, (struct sockaddr *)&cliaddr, &clilen);
               if(connfd < 0)
               {
                   perror("accept error");
                   continue;
               }

             printf("connection from %s, port is %d\n", inet_ntop(AF_INET,&cliaddr.sin_addr,buf,sizeof(buf)),ntohs(cliaddr.sin_port));
               ev.events = EPOLLIN|EPOLLET;
               ev.data.fd = connfd;
               if(epoll_ctl(epollfd, EPOLL_CTL_ADD, connfd, &ev) < 0)
               {
                   fprintf(stderr, "epoll set insertion error: fd = %d\n", connfd);
                   return -1;
               }

           }
           else   //operate socket
           {
               int n;
               int sockfd = events[i].data.fd;

               if(events[i].events & EPOLLIN)   //fd is readable
               {
                   bzero(buf, MAXLINE);
                   //printf("EPOLLIN readable\n");
                   if(sockfd < 0)
                       continue;

                   if((n = read(sockfd, buf, MAXLINE)) < 0)
                   {
                       close(sockfd);
                       sockfd = -1;
                       perror("read error");
                       return ;
                   }
                   else if(n == 0)
                   {
                       printf("terminated from port %d\n", ntohs(cliaddr.sin_port));
                       close(sockfd);
                       sockfd = -1;
                   }
                   else
                   {
                       printf("read %d characters\n", n - 1);
                       ev.data.fd = sockfd;
                       ev.events = EPOLLOUT|EPOLLET;//这里的LIN,变成了OUT。此fd接下来主要为了输出

epoll_ctl(epollfd, EPOLL_CTL_MOD, sockfd, &ev);//这里的sokfd是已经建立连接的fd，且数据已经被读过，

//所以这里用EPOLL_CTL_MOD这个参数
                   }
               }
               if(events[i].events & EPOLLOUT)   //读完之后的fd,events事件被修改过了EPOLLOUT
               {
                   //printf("EPOLLOUT writeable\n");
                   if(sockfd < 0)
                       continue;

                   if((n = write(sockfd, buf, strlen(buf))) < 0)
                   {
                       perror("write error");
                       return ;
                   }
                   else
                   {
                       printf("write %d characters\n", (n - 1) > 0?(n-1):0);
                       ev.data.fd = sockfd;
                       ev.events = EPOLLIN|EPOLLET;
                       bzero(buf, n);
                       epoll_ctl(epollfd, EPOLL_CTL_MOD, sockfd, &ev);
                   }
               }
           }
       }
   }

   return 0;
}