网络编程-epoll模型

#include <stdio.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <fcntl.h>
#include <pthread.h>
#include <unistd.h>
#include <sys/epoll.h>
#include <string.h>
#define BUFFER_LENGTH 128
#define EVENTS_LENGTH 128
char rbuffer[BUFFER_LENGTH] = {0};
char wbuffer[BUFFER_LENGTH] = {0};
int main()
{
    int listenfd = socket(AF_INET, SOCK_STREAM, 0);
    if (listenfd == -1) return -1;
    struct sockaddr_in servaddr;
    servaddr.sin_family = AF_INET;
    servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
    servaddr.sin_port = htons(9999);
    if (-1 == bind(listenfd, (struct sockaddr*)&servaddr, sizeof(servaddr)))
    {
        return -2;
    }
#if 0 //nonblock
    int flag = fcntl(listenfd, F_GETFL, 0);
    flag |= O_NONBLOCK;
    fcntl(listenfd, F_SETFL, flag);
#endif
    listen(listenfd, 10);
    int epfd = epoll_create(1);
    struct epoll_event ev, events[EVENTS_LENGTH];
    ev.events = EPOLLIN;
    ev.data.fd = listenfd;
    epoll_ctl(epfd, EPOLL_CTL_ADD, listenfd, &ev);
    //printf("fd: %d\n", epfd);
    while (1) {
        int nready = epoll_wait(epfd, events, EVENTS_LENGTH, -1);
        //printf("nready: %d\n", nready);
        for (int i = 0; i < nready; i++) {
            int clientfd = events[i].data.fd;
            if (listenfd == clientfd) {//accept
                    struct sockaddr_in client;
                    socklen_t len = sizeof(client);
                    int connfd = accept(listenfd, (struct sockaddr*)&client, &len);
                    printf("accept: %d\n", connfd);
                    //默认水平触发
                    ev.events = EPOLLIN/* | EPOLLET*/;
                    ev.data.fd = connfd;
                    epoll_ctl(epfd, EPOLL_CTL_ADD, connfd, &ev);
            } else if (events[i].events & EPOLLIN){//clientfd
                int n = recv(clientfd, rbuffer, BUFFER_LENGTH, 0);
                if (n > 0) {
                    rbuffer[n] = '\0';
                    printf("recv: %s, length = %d\n", rbuffer, n);
                    memcpy(wbuffer, rbuffer, BUFFER_LENGTH);
                    ev.events = EPOLLOUT;
                    ev.data.fd = clientfd;
                    epoll_ctl(epfd, EPOLL_CTL_MOD, clientfd, &ev);
                }  
            } else if (events[i].events & EPOLLOUT) {
                send(clientfd, wbuffer, BUFFER_LENGTH, 0);
                ev.events = EPOLLIN;
                ev.data.fd = clientfd;
                epoll_ctl(epfd, EPOLL_CTL_MOD, clientfd, &ev);
            }
        }
    }
    return 0;
}