epoll 服务器解析

typedef union epoll_data{
		void *ptr;
  	int fd;
  	uint32_t u32;
  	uint64_t u64; 		
}epoll_data_t;
struct epoll_event{
  uint32_t events;
  epoll_data_t data;
}

#include <iostream>
#include <netinet/in.h>
#include <sys/socket.h>
#include <sys/epoll.h>
#include <unistd.h>
#include <fcntl.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <sys/types.h>
#include <errno.h>
#define PORT 8111
#define MESSAGE_LEN 1024
#define MAX_EVENTS 20
#define TIMEOUT 500
using  std::cout;
using  std::endl;
int main(int arc, char *argv[]) {
    int ret = -1;
    int socket_fd , accept_fd;
    int on = 1;
    int backlog = 10;
    int flags = 1;
    char in_buff[MESSAGE_LEN] = {0,};
    struct sockaddr_in localaddr,remoteaddr;
    struct epoll_event ev,events[MAX_EVENTS];
    int epoll_fd;
    int event_number;
    //1 创建一个socket
    socket_fd = socket(AF_INET, SOCK_STREAM, 0);
    if (socket_fd == -1) {
        cout << "Failed to create socket!" << endl;
        exit(-1);
    }
    flags = fcntl(socket_fd,F_GETFL,0);//设置为非阻塞
    fcntl(socket_fd,F_SETFL,flags| O_NONBLOCK);
  
    //2 SO_REUSEADDR 允许套接口和一个已在使用中的地址捆绑
    ret = setsockopt(socket_fd,
                     SOL_SOCKET,
                     SO_REUSEADDR,
                     &flags,
                     sizeof(flags));
    if (ret == -1) {
        cout << "Failed to set socket options" << endl;
    }
  
    // 3 选择协议端口
    localaddr.sin_family = AF_INET;
    localaddr.sin_port = PORT;
    localaddr.sin_addr.s_addr = INADDR_ANY;
//    绑定
    ret = bind(socket_fd, (struct sockaddr *) &localaddr, sizeof(struct sockaddr));
    if (ret == -1) {
        cout << "Failed to bind addr!" << endl;
        exit(-1);
    }
//    侦听
    ret = listen(socket_fd, backlog);
    if (ret == -1) {
        cout << " Failed to listen socket!" << endl;
        exit(-1);
    }
    //4 使用epoll添加事件
    //一个新的事件发生了，是EPOLLIN写入操作；知道data.fd是哪个文件发生，如果新的连接来了就要做创建连接准备
    epoll_fd = epoll_create(256);
    ev.events = EPOLLIN;
    ev.data.fd = socket_fd;
//    添加侦听的描述符
    epoll_ctl(epoll_fd,EPOLL_CTL_ADD,socket_fd,&ev);
    for (;;) {
//有多少个文件描述符发生events（事件了）
        event_number =  epoll_wait(epoll_fd,events,MAX_EVENTS,TIMEOUT);
        for (int i = 0; i < event_number; ++i) {
            if (events[i].data.fd == socket_fd){//说明是一个侦听的socket，需要创建新的连接
                socklen_t addr_len = sizeof(struct sockaddr_in);
                accept_fd = accept(socket_fd,
                                   (struct sockaddr *) &remoteaddr,
                                   &addr_len);
//                设置为 非阻塞
                flags = fcntl(accept_fd,F_GETFL,0);
                fcntl(accept_fd,F_SETFL,flags| O_NONBLOCK);
                ev.events = EPOLLIN | EPOLLET;
                ev.data.fd = accept_fd;
                epoll_ctl(epoll_fd,EPOLL_CTL_ADD,accept_fd,&ev);
            }else if (events[i].events & EPOLLIN){
                do {
                    memset(in_buff,0,MESSAGE_LEN);
                    //接受网络数据并打印
                    ret = recv(events[i].data.fd, (void *) in_buff, MESSAGE_LEN, 0);
                    if (ret == 0)//没有发数据和我们断开连接了
                    {
                        close(events[i].data.fd);
                        break;
                    }
                    if (ret == MESSAGE_LEN){//缓冲区满了
                        cout<< "maybe have data..."<<endl;
                    }
                }while (ret<-1 && errno == EINTR);
                if (ret <0){
                    switch (errno) {
                        case EAGAIN: //说明暂时已经没有数据了，要等通知
                            break;
                        case EINTR: //被终断了，再来一次
                            printf("recv EINTR... \n");
                            ret = recv(events[i].data.fd, &in_buff, MESSAGE_LEN, 0);
                            break;
                        default:
                            printf("the client is closed, fd:%d\n", events[i].data.fd);
                            epoll_ctl(epoll_fd, EPOLL_CTL_DEL, events[i].data.fd, &ev);
                            close(events[i].data.fd);
                            ;
                    }
                }
                    cout << "rev message:" << in_buff << endl;
                    send(events[i].data.fd, (void *) in_buff, MESSAGE_LEN, 0);
            }
        }
    }
//    把socket关闭
    cout<<"quit server...\n"<<endl;
    close(socket_fd);
    return 0;
}

flags = fcntl(socket_fd,F_GETFL,0);//设置为非阻塞
    fcntl(socket_fd,F_SETFL,flags| O_NONBLOCK);