linux c epoll

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <sys/epoll.h>

#define EPOLL_SIZE 5

int main(int argc, char* argv[])
{
    int client_fd;
    int epoll_fd = 0;
    int listen_fd;
    int res = 0;
    int opt = 1;
    socklen_t clientaddr_len;
    struct sockaddr_in serveraddr;
    struct sockaddr_in clientaddr;
    int read_len = 0;
    int i = 0;
    char szbuff[1024];    
    if (argc < 2)
    {
        printf("usgae: %s port\n", argv[0]);
        return -1;
    }
    listen_fd = socket(AF_INET, SOCK_STREAM, 0);
    if (listen_fd < 0)
    {
        perror("socket error");
        return -1;
    }
    /* 端口重複利用 */
    setsockopt(listen_fd, SOL_SOCKET, SO_REUSEADDR, (void*)&opt, sizeof(opt));
    serveraddr.sin_family = AF_INET;
    serveraddr.sin_port = htons(atoi(argv[1]));
    serveraddr.sin_addr.s_addr = INADDR_ANY;
    
    res = bind(listen_fd, (struct sockaddr*)&serveraddr, sizeof(struct sockaddr));
    if (res != 0)
    {
        perror("bind error");
        return -1;
    }
    res = listen(listen_fd, 10);
    if (res != 0)
    {
        perror("listen error");
        return -1;
    }
    
    clientaddr_len = sizeof(struct sockaddr_in);
    epoll_fd = epoll_create(EPOLL_SIZE);
    struct epoll_event ev;
    struct epoll_event *ep_events =  NULL;
    ep_events = (struct epoll_event*)malloc(sizeof(struct epoll_event)*EPOLL_SIZE);
    if (ep_events == NULL)
    {
        perror("malloc");
        return -1;
    }
    memset(&ev, 0x00, sizeof(struct epoll_event));
    memset(ep_events, 0x00, sizeof(struct epoll_event));
    ev.events = EPOLLIN;
    ev.data.fd = listen_fd;
    res = epoll_ctl(epoll_fd, EPOLL_CTL_ADD, listen_fd, &ev);
    if (res != 0)
    {
        perror("epoll_ctl error");
        return -1;
    }
    while(1)
    {
        res = epoll_wait(epoll_fd, ep_events, EPOLL_SIZE, -1);
        if (res > 0)
        {
            for (i = 0; i<res; i++)
            {
                if (ep_events[i].events & EPOLLIN)
                {
                    if (ep_events[i].data.fd == listen_fd)
                    {
                        client_fd = accept(listen_fd, (struct sockaddr*)&clientaddr, &clientaddr_len);
                        if (client_fd < 0)
                        {
                            perror("client_fd error");
                            return -1;
                        }
                        printf("client_fd=%d has connect success\n", client_fd);
                        ev.events = EPOLLIN | EPOLLET;
                        ev.data.fd = client_fd;
                        res = epoll_ctl(epoll_fd, EPOLL_CTL_ADD, client_fd, &ev);
                        if (res != 0)
                        {
                            perror("epoll_ctl error");
                            return -1;
                        }
                    }
                    else
                    {
                        memset(szbuff, 0x00, sizeof(szbuff));
                        read_len = read(ep_events[i].data.fd, szbuff, sizeof(szbuff)-1);    
                        if (read_len == 0)
                        {
                            epoll_ctl(epoll_fd, EPOLL_CTL_DEL, ep_events[i].data.fd, ep_events);
                            close(ep_events[i].data.fd);
                            printf("fd=%d has closed\n", ep_events[i].data.fd);
                            continue;
                        }
                        else if (read_len < 0)
                        {
                            printf("__LINE__====%d\n", __LINE__);
                            return -1;
                        }
                        printf("fd=%d, msg=%s\n", ep_events[i].data.fd, szbuff);
                    }
                }
            }
        }
    }
    close(listen_fd);
    return 0;
}