【Linux C TCP服务器端-epoll案例】

#include <errno.h>
#include <netinet/in.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <unistd.h>
#include <sys/epoll.h>
#define MAXLNE  4096
#define POLL_SIZE 1024
int main(int argc, char **argv) 
{
    int listenfd, connfd, n;
    struct sockaddr_in servaddr;
    char buff[MAXLNE];
    if ((listenfd = socket(AF_INET, SOCK_STREAM, 0)) == -1) {
        printf("create socket error: %s(errno: %d)\n", strerror(errno), errno);
        return 0;
    }
    memset(&servaddr, 0, sizeof(servaddr));
    servaddr.sin_family = AF_INET;
    servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
    servaddr.sin_port = htons(9999);
    if (bind(listenfd, (struct sockaddr *)&servaddr, sizeof(servaddr)) == -1) {
        printf("bind socket error: %s(errno: %d)\n", strerror(errno), errno);
        return 0;
    }
    //listen接口之后会一直监听客户端的连接，每次客户端连接，都会和其创建连接（三次连接时内核完成的，不是由应用程序去控制的）
  //三次握手不发生在任何API中，协议栈本身被动完成的。
    if (listen(listenfd, 10) == -1) {
        printf("listen socket error: %s(errno: %d)\n", strerror(errno), errno);
        return 0;
    }
  //poll/select -->
  //7*24 不间断的检测I/O是否有数据到达 
  // epoll_create  
  // epoll_ctl(ADD, DEL, MOD)  搬进，搬出，修改
  // epoll_wait 
  int epfd = epoll_create(1); //int size -早期这个参数有用-是数组，现在是一个链表，后面这个参数没用（兼容保留了）
  //每次能够检测的最大事件个数，如果大于POLL_SIZE,while循环时会多检测几次
  struct epoll_event events[POLL_SIZE] = {0};
  struct epoll_event ev;
  ev.events = EPOLLIN;
  ev.data.fd = listenfd;
  epoll_ctl(epfd, EPOLL_CTL_ADD, listenfd, &ev);
  while (1) {
  int nready = epoll_wait(epfd, events, POLL_SIZE, 5);
  if (nready == -1) {
    continue;
  }
  int i = 0;
  for (i = 0;i < nready;i ++) {
    int clientfd =  events[i].data.fd;
    if (clientfd == listenfd) {
    struct sockaddr_in client;
       socklen_t len = sizeof(client);
       if ((connfd = accept(listenfd, (struct sockaddr *)&client, &len)) == -1) {
           printf("accept socket error: %s(errno: %d)\n", strerror(errno), errno);
           return 0;
       }
    printf("accept\n");
    ev.events = EPOLLIN;
    ev.data.fd = connfd;
    epoll_ctl(epfd, EPOLL_CTL_ADD, connfd, &ev);
    } else if (events[i].events & EPOLLIN) {
    n = recv(clientfd, buff, MAXLNE, 0);
          if (n > 0) {
              buff[n] = '\0';
              printf("recv msg from client: %s\n", buff);
      send(clientfd, buff, n, 0);
          } else if (n == 0) { //
      ev.events = EPOLLIN;
      ev.data.fd = clientfd;
      epoll_ctl(epfd, EPOLL_CTL_DEL, clientfd, &ev);
              close(clientfd);  
          }
    }
  }
  }
    close(listenfd);
    return 0;
}