epoll完整例子

本文展示了一个使用C语言编写的简单Epoll服务器程序实例。该程序利用socket、epoll等技术实现了一个能够监听并处理客户端连接请求的服务端应用。通过设置socket为非阻塞模式,并采用边缘触发模式监听连接和读事件,提高了服务器的并发处理能力。

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#include <sys/socket.h>

#include <sys/epoll.h>

#include <netinet/in.h>

#include <arpa/inet.h>

#include <fcntl.h>

#include <unistd.h>

#include <stdio.h>

#include <errno.h>

#define MAXLINE 100

void
setnonblocking (int sock)
{
  int opts = 0;
  opts = fcntl (sock, F_GETFL);
  if (opts < 0)
  {
  perror ("fcntl get failed!");
  return;
  }
  opts = opts | O_NONBLOCK;
  if (fcntl (sock, F_SETFL, opts) < 0)
  {
  perror ("fcntl set failed!");
  return;
  }
}

int
main ()
{
  int i, maxi, listenfd, connfd, sockfd, epfd, nfds;
  size_t n;
  char line[1024];
  socklen_t clilen;
  struct epoll_event ev, events[20];
  epfd = epoll_create (256);
  struct sockaddr_in clientaddr;
  struct sockaddr_in serveraddr;
  listenfd = socket (AF_INET, SOCK_STREAM, 0);
  setnonblocking (listenfd);

  ev.data.fd = listenfd;
  ev.events = EPOLLIN | EPOLLET;
  epoll_ctl (epfd, EPOLL_CTL_ADD, listenfd, &ev);

  serveraddr.sin_family = AF_INET;
  serveraddr.sin_port = htons (8888);
  inet_aton ("202.117.10.184", &(serveraddr.sin_addr));
  bind (listenfd, (struct sockaddr *) &serveraddr, sizeof (serveraddr));
  listen (listenfd, 20);
  maxi = 0;
  for (;;)
  {
  nfds = epoll_wait (epfd, events, 20, -1);
  for (i = 0; i < nfds; i++)
 {
  if (events[i].data.fd == listenfd)
  {
  clilen = sizeof (clientaddr);
  connfd =
  accept (listenfd, (struct sockaddr *) &clientaddr, &clilen);
  if (connfd < 0)
  {
  perror ("connfd < 0");
  return 1;
  }
  setnonblocking (connfd);
  fprintf (stdout, "connect form: %s/n",
  inet_ntoa (clientaddr.sin_addr));
  ev.data.fd = connfd;
  ev.events = EPOLLIN | EPOLLET;
  epoll_ctl (epfd, EPOLL_CTL_ADD, connfd, &ev);
  }
  else if (events[i].events & EPOLLIN)
  {
  if ((sockfd = events[i].data.fd) < 0)
  continue;
  if ((n = read (sockfd, line, sizeof (line))) < 0)
  {
  if (ECONNRESET == errno)
  {
  close (sockfd);
  events[i].data.fd = -1;
  }
  else
  {
  fprintf (stderr, "readerror!");
  }
  }
  else if (0 == n)
  {
  close (sockfd);
  events[i].data.fd = -1;
  }
  else
  {
  line[n] = '/0';
  fprintf (stdout, "read: %s/n", line);
  }
  ev.data.fd = sockfd;
  ev.events = EPOLLOUT | EPOLLET;
  epoll_ctl (epfd, EPOLL_CTL_MOD, sockfd, &ev);
  }
  else if (events[i].events & EPOLLOUT)
  {
  n = strlen (line);
  sockfd = events[i].data.fd;
  write (sockfd, line, n);
  ev.data.fd = sockfd;
  ev.events = EPOLLIN | EPOLLET;
  epoll_ctl (epfd, EPOLL_CTL_MOD, sockfd, &ev);
  }
 }
  }
  return 0;
}

Boost库虽然包含了epoll的支持,但在标准C++11引入了asio库后,更推荐使用asio来做跨平台的事件驱动编程,包括epoll。但如果你坚持要使用Boost的Epoll,这里是一个简单的例子展示如何在Boost环境中创建一个epoll实例并监听文件描述符: 首先,你需要包含必要的头文件,并链接到Boost库: ```cpp #include <boost/asio.hpp> #include <vector> using boost::asio::ip::tcp; using boost::asio::io_service; void handle_events(const boost::system::error_code& ec) { if (!ec) { std::cout << "Event occurred" << std::endl; } } int main() { try { io_service ios; boost::asio::epoll_event event; event.events = boost::asio::epoll_event::in | boost::asio::epoll_event::out; boost::asio::epoll epoll_socket; epoll_socket.open(boost::asio::epoll::flag_type::epoll_create(1)); tcp::acceptor acceptor(ios, tcp::endpoint(tcp::v4(), 8080)); while (true) { std::vector<boost::asio::epoll_event> events; epoll_socket.poll(events, boost::asio::epoll::wait_all); for (const auto& e : events) { if (e.events & boost::asio::epoll_event::in) { acceptor.accept(event.socket()); event.data.fd = event.socket().lowest_layer().native(); epoll_socket.modify(event.data.fd, boost::asio::epoll_event::events, boost::asio::epoll_event::in); } if (e.events & boost::asio::epoll_event::out) { std::cout << "Write to socket with descriptor " << e.data.fd << std::endl; } if (handle_events(e)) { break; // 用户处理事件后退出循环 } } } } catch (std::exception& e) { std::cerr << "Error: " << e.what() << std::endl; } return 0; } ``` 这个例子中,我们创建了一个epoll实例,监听一个TCP端口。每当有新的连接请求或旧的连接准备好发送数据时,epoll都会触发相应的事件。你需要自定义`handle_events`函数来处理具体的事件。
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