struct eventpoll{..../*红黑树的根节点，这颗树中存储着所有添加到epoll中的需要监控的事件*/struct rb_root  rbr;/*双链表中则存放着将要通过epoll_wait返回给用户的满足条件的事件*/struct list_head rdlist;....
};

struct epitem{struct rb_node  rbn;//红黑树节点struct list_head    rdllink;//双向链表节点struct epoll_filefd  ffd;  //事件句柄信息struct eventpoll *ep;    //指向其所属的eventpoll对象struct epoll_event event; //期待发生的事件类型
}

typedef union epoll_data {  
void *ptr;  
int fd;  
__uint32_t u32;  
__uint64_t u64;  
} epoll_data_t;  struct epoll_event {  
__uint32_t events; /* Epoll events */  
epoll_data_t data; /* User data variable */  
};

struct epoll_event ev;
//设置与要处理的事件相关的文件描述符
ev.data.fd=listenfd;
//设置要处理的事件类型
ev.events=EPOLLIN|EPOLLET;
//注册epoll事件
epoll_ctl(epfd,EPOLL_CTL_ADD,listenfd,&ev);

/*
*   file epollTest.c
*/
#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: %sn", 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 bindn");  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 errorn");  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 %dn",  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;  
}
代码编译后，./epollTest 8888 ,在另外一个终端中执行 
telnet 192.168.1.161 8888 ，192.168.1.161为执行测试程序的ip。在telnet终端敲入任何字符敲入Enter后，会在测试终端显示敲入的字符