epoll实例

epoll的程序实例

 #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
staticint
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
staticint
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;
            }

elseif (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;
                    }
elseif (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;
}