#define IPADDRESS   "127.0.0.1"#define PORT        8787#define MAXSIZE     1024#define LISTENQ     5#define FDSIZE      1000#define EPOLLEVENTS 100listenfd = socket_bind(IPADDRESS,PORT);struct epoll_event events[EPOLLEVENTS];//创建一个描述符epollfd = epoll_create(FDSIZE);//添加监听描述符事件add_event(epollfd,listenfd,EPOLLIN);//循环等待for ( ; ; ){    //该函数返回已经准备好的描述符事件数目    ret = epoll_wait(epollfd,events,EPOLLEVENTS,-1);    //处理接收到的连接    handle_events(epollfd,events,ret,listenfd,buf);}//事件处理函数static void handle_events(int epollfd,struct epoll_event *events,int num,int listenfd,char *buf){     int i;     int fd;     //进行遍历;这里只要遍历已经准备好的io事件。num并不是当初epoll_create时的FDSIZE。     for (i = 0;i < num;i++)     {         fd = events[i].data.fd;        //根据描述符的类型和事件类型进行处理         if ((fd == listenfd) &&(events[i].events & EPOLLIN))            handle_accpet(epollfd,listenfd);         else if (events[i].events & EPOLLIN)            do_read(epollfd,fd,buf);         else if (events[i].events & EPOLLOUT)            do_write(epollfd,fd,buf);     }}//添加事件static void add_event(int epollfd,int fd,int state){    struct epoll_event ev;    ev.events = state;    ev.data.fd = fd;    epoll_ctl(epollfd,EPOLL_CTL_ADD,fd,&ev);}//处理接收到的连接。将文件描述符添加到epoll监控队列static void handle_accpet(int epollfd,int listenfd){     int clifd;          struct sockaddr_in cliaddr;          socklen_t  cliaddrlen;          clifd = accept(listenfd,(struct sockaddr*)&cliaddr,&cliaddrlen);          if (clifd == -1)                  perror("accpet error:");          else {                  printf("accept a new client: %s:%d\n",inet_ntoa(cliaddr.sin_addr),cliaddr.sin_port);  //添加一个客户描述符和事件                  add_event(epollfd,clifd,EPOLLIN);          } }//读处理static void do_read(int epollfd,int fd,char *buf){    int nread;    nread = read(fd,buf,MAXSIZE);    if (nread == -1)     {                 perror("read error:");                 close(fd); //记住close fd                delete_event(epollfd,fd,EPOLLIN); //删除监听     }    else if (nread == 0)     {                 fprintf(stderr,"client close.\n");        close(fd); //记住close fd               delete_event(epollfd,fd,EPOLLIN); //删除监听     }         else {                 printf("read message is : %s",buf);                //修改描述符对应的事件，由读改为写                 modify_event(epollfd,fd,EPOLLOUT);         } }//写处理static void do_write(int epollfd,int fd,char *buf) {         int nwrite;         nwrite = write(fd,buf,strlen(buf));         if (nwrite == -1){                 perror("write error:");                close(fd);   //记住close fd               delete_event(epollfd,fd,EPOLLOUT);  //删除监听        }else{        modify_event(epollfd,fd,EPOLLIN);     }        memset(buf,0,MAXSIZE); }//删除事件static void delete_event(int epollfd,int fd,int state) {    struct epoll_event ev;    ev.events = state;    ev.data.fd = fd;    epoll_ctl(epollfd,EPOLL_CTL_DEL,fd,&ev);}//修改事件static void modify_event(int epollfd,int fd,int state){         struct epoll_event ev;    ev.events = state;    ev.data.fd = fd;    epoll_ctl(epollfd,EPOLL_CTL_MOD,fd,&ev);}//注：另外一端我就省了