epoll实例

edge triggered(ET:边缘),level triggered(LT:水平)模式

几乎所有的epoll程序都使用下面的框架：

[cpp] view plain copy

1. for( ; ; )  
2.    {  
3.        nfds = epoll_wait(epfd,events,20,500);  
4.        for(i=0;i<nfds;++i)  
5.        {  
6.            if(events[i].data.fd==listenfd) //有新的连接  
7.            {  
8.                connfd = accept(listenfd,(sockaddr *)&clientaddr, &clilen); //accept这个连接  
9.                ev.data.fd=connfd;  
10.                ev.events=EPOLLIN|EPOLLET;  
11.                epoll_ctl(epfd,EPOLL_CTL_ADD,connfd,&ev); //将新的fd添加到epoll的监听队列中  
12.            }  
13.   
14.            else if( events[i].events&EPOLLIN ) //接收到数据，读socket  
15.            {  
16.                n = read(sockfd, line, MAXLINE)) < 0    //读  
17.                ev.data.ptr = md;     //md为自定义类型，添加数据  
18.                ev.events=EPOLLOUT|EPOLLET;  
19.                epoll_ctl(epfd,EPOLL_CTL_MOD,sockfd,&ev);//修改标识符，等待下一个循环时发送数据，异步处理的精髓  
20.            }  
21.            else if(events[i].events&EPOLLOUT) //有数据待发送，写socket  
22.            {  
23.                struct myepoll_data* md = (myepoll_data*)events[i].data.ptr;    //取数据  
24.                sockfd = md->fd;  
25.                send( sockfd, md->ptr, strlen((char*)md->ptr), 0 );        //发送数据  
26.                ev.data.fd=sockfd;  
27.                ev.events=EPOLLIN|EPOLLET;  
28.                epoll_ctl(epfd,EPOLL_CTL_MOD,sockfd,&ev); //修改标识符，等待下一个循环时接收数据  
29.            }  
30.            else  
31.            {  
32.                //其他的处理  
33.            }  
34.        }  
35.    }  

epoll实例

#include <stdio.h>

#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <sys/socket.h>
#include <netdb.h>
#include <fcntl.h>
#include <sys/epoll.h>
#include <string.h>


#define MAXEVENTS 64


//函数:
//功能:创建和绑定一个TCP socket
//参数:端口
//返回值:创建的socket
static int
create_and_bind (char *port)
{
  struct addrinfo hints;
  struct addrinfo *result, *rp;
  int s, sfd;


  memset (&hints, 0, sizeof (struct addrinfo));
  hints.ai_family = AF_UNSPEC;     /* Return IPv4 and IPv6 choices */
  hints.ai_socktype = SOCK_STREAM; /* We want a TCP socket */
  hints.ai_flags = AI_PASSIVE;     /* All interfaces */


  s = getaddrinfo (NULL, port, &hints, &result);
  if (s != 0)
    {
      fprintf (stderr, "getaddrinfo: %s\n", gai_strerror (s));
      return -1;
    }


  for (rp = result; rp != NULL; rp = rp->ai_next)
    {
      sfd = socket (rp->ai_family, rp->ai_socktype, rp->ai_protocol);
      if (sfd == -1)
        continue;


      s = bind (sfd, rp->ai_addr, rp->ai_addrlen);
      if (s == 0)
        {
          /* We managed to bind successfully! */
          break;
        }


      close (sfd);
    }


  if (rp == NULL)
    {
      fprintf (stderr, "Could not bind\n");
      return -1;
    }


  freeaddrinfo (result);


  return sfd;
}




//函数
//功能:设置socket为非阻塞的
static int
make_socket_non_blocking (int sfd)
{
  int flags, s;


  //得到文件状态标志
  flags = fcntl (sfd, F_GETFL, 0);
  if (flags == -1)
    {
      perror ("fcntl");
      return -1;
    }


  //设置文件状态标志
  flags |= O_NONBLOCK;
  s = fcntl (sfd, F_SETFL, flags);
  if (s == -1)
    {
      perror ("fcntl");
      return -1;
    }


  return 0;
}


//端口由参数argv[1]指定
int
main (int argc, char *argv[])
{
  int sfd, s;
  int efd;
  struct epoll_event event;
  struct epoll_event *events;


  if (argc != 2)
    {
      fprintf (stderr, "Usage: %s [port]\n", argv[0]);
      exit (EXIT_FAILURE);
    }


  sfd = create_and_bind (argv[1]);
  if (sfd == -1)
    abort ();


  s = make_socket_non_blocking (sfd);
  if (s == -1)
    abort ();


  s = listen (sfd, SOMAXCONN);
  if (s == -1)
    {
      perror ("listen");
      abort ();
    }


  //除了参数size被忽略外,此函数和epoll_create完全相同
  efd = epoll_create1 (0);
  if (efd == -1)
    {
      perror ("epoll_create");
      abort ();
    }


  event.data.fd = sfd;
  event.events = EPOLLIN | EPOLLET;//读入,边缘触发方式
  s = epoll_ctl (efd, EPOLL_CTL_ADD, sfd, &event);
  if (s == -1)
    {
      perror ("epoll_ctl");
      abort ();
    }


  /* Buffer where events are returned */
  events = calloc (MAXEVENTS, sizeof event);


  /* The event loop */
  while (1)
    {
      int n, i;


      n = epoll_wait (efd, events, MAXEVENTS, -1);
      for (i = 0; i < n; i++)
        {
          if ((events[i].events & EPOLLERR) ||
              (events[i].events & EPOLLHUP) ||
              (!(events[i].events & EPOLLIN)))
            {
              /* An error has occured on this fd, or the socket is not
                 ready for reading (why were we notified then?) */
              fprintf (stderr, "epoll error\n");
              close (events[i].data.fd);
              continue;
            }


          else if (sfd == events[i].data.fd)
            {
              /* We have a notification on the listening socket, which
                 means one or more incoming connections. */
              while (1)
                {
                  struct sockaddr in_addr;
                  socklen_t in_len;
                  int infd;
                  char hbuf[NI_MAXHOST], sbuf[NI_MAXSERV];


                  in_len = sizeof in_addr;
                  infd = accept (sfd, &in_addr, &in_len);
                  if (infd == -1)
                    {
                      if ((errno == EAGAIN) ||
                          (errno == EWOULDBLOCK))
                        {
                          /* We have processed all incoming
                             connections. */
                          break;
                        }
                      else
                        {
                          perror ("accept");
                          break;
                        }
                    }


                                  //将地址转化为主机名或者服务名
                  s = getnameinfo (&in_addr, in_len,
                                   hbuf, sizeof hbuf,
                                   sbuf, sizeof sbuf,
                                   NI_NUMERICHOST | NI_NUMERICSERV);//flag参数:以数字名返回
                                  //主机地址和服务地址


                  if (s == 0)
                    {
                      printf("Accepted connection on descriptor %d "
                             "(host=%s, port=%s)\n", infd, hbuf, sbuf);
                    }


                  /* Make the incoming socket non-blocking and add it to the
                     list of fds to monitor. */
                  s = make_socket_non_blocking (infd);
                  if (s == -1)
                    abort ();


                  event.data.fd = infd;
                  event.events = EPOLLIN | EPOLLET;
                  s = epoll_ctl (efd, EPOLL_CTL_ADD, infd, &event);
                  if (s == -1)
                    {
                      perror ("epoll_ctl");
                      abort ();
                    }
                }
              continue;
            }
          else
            {
              /* We have data on the fd waiting to be read. Read and
                 display it. We must read whatever data is available
                 completely, as we are running in edge-triggered mode
                 and won't get a notification again for the same
                 data. */
              int done = 0;


              while (1)
                {
                  ssize_t count;
                  char buf[512];


                  count = read (events[i].data.fd, buf, sizeof(buf));
                  if (count == -1)
                    {
                      /* If errno == EAGAIN, that means we have read all
                         data. So go back to the main loop. */
                      if (errno != EAGAIN)
                        {
                          perror ("read");
                          done = 1;
                        }
                      break;
                    }
                  else if (count == 0)
                    {
                      /* End of file. The remote has closed the
                         connection. */
                      done = 1;
                      break;
                    }


                  /* Write the buffer to standard output */
                  s = write (1, buf, count);
                  if (s == -1)
                    {
                      perror ("write");
                      abort ();
                    }
                }


              if (done)
                {
                  printf ("Closed connection on descriptor %d\n",
                          events[i].data.fd);


                  /* Closing the descriptor will make epoll remove it
                     from the set of descriptors which are monitored. */
                  close (events[i].data.fd);
                }
            }
        }
    }


  free (events);


  close (sfd);


  return EXIT_SUCCESS;
}