Пример кода epoll

Очень базовый пример обработки входящих соединений с epoll:

#include <stdio.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <sys/epoll.h>
#include <sys/socket.h>
#include <strings.h>

#define EPOLL_RUN_TIMEOUT 1000
#define MAXEVENTS 50

int got_connect(fd) {
   printf("got data\n");
   return 0;
}

int main(int argc, char *argv[]){
   if(argc<2){
       printf("Usage: %s <port>\n",argv[0]);
       return -1;
   }

   int port=atoi(argv[1]);
   int epfd = epoll_create(512);
   int nfds, cs, i;

   struct epoll_event ev, *events;
   struct sockaddr_in serv, cli;
   int connected_fd;
   int listenfd=socket(AF_INET, SOCK_STREAM, 0);

   bzero(&serv,sizeof(serv));
   serv.sin_family = AF_INET;
   serv.sin_addr.s_addr = htonl(INADDR_ANY);
   serv.sin_port = htons(port);

   bind(listenfd,(struct sockaddr*)&serv,sizeof(serv));
   listen(listenfd, 50);

   ev.events = EPOLLIN | EPOLLET | EPOLLHUP;
   ev.data.fd = listenfd;
   epoll_ctl(epfd, EPOLL_CTL_ADD, listenfd, &ev);
   int addrlen = sizeof(cli);

   while(1){
       nfds = epoll_wait(epfd,events,MAXEVENTS,EPOLL_RUN_TIMEOUT);
       if(nfds<0){
           printf("epoll_wait error\n");
           return -1;
       }
       for (i=0;i<nfds;++i){
           if(events[i].data.fd == listenfd){
               connected_fd = accept(listenfd, (struct sockaddr *) &cli,&addrlen);
               printf("addr: %s\n",inet_ntoa(cli.sin_addr.s_addr));
               ev.events = EPOLLIN | EPOLLET;
               ev.data.fd = connected_fd;
               epoll_ctl(epfd, EPOLL_CTL_ADD, connected_fd, &ev);
           }
           else{
               got_connect(events[i].data.fd);
           }
       }
   }
   close(epfd);
   return 0;
}

Сцылки по теме:
http://www.kegel.com/c10k.html
http://www.monkey.org/~provos/libevent/
http://www.xmailserver.org/linux-patches/nio-improve.html