linux epoll例程

#include <sys/epoll.h>
#include <unistd.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define MAX_EVENTS 10
#define PORT 8080

int set_nonblocking(int fd) {
    int flags = fcntl(fd, F_GETFL, 0);
    if (flags == -1) return -1;
    flags |= O_NONBLOCK;
    return fcntl(fd, F_SETFL, flags);
}

int main() {
    int listen_fd = socket(AF_INET, SOCK_STREAM, 0);
    if (listen_fd == -1) perror("socket");

    struct sockaddr_in server_addr;
    memset(&server_addr, 0, sizeof(server_addr));
    server_addr.sin_family = AF_INET;
    server_addr.sin_addr.s_addr = INADDR_ANY;
    server_addr.sin_port = htons(PORT);

    if (bind(listen_fd, (struct sockaddr*)&server_addr, sizeof(server_addr)) == -1) perror("bind");

    if (listen(listen_fd, SOMAXCONN) == -1) perror("listen");

    int epoll_fd = epoll_create1(0);
    if (epoll_fd == -1) perror("epoll_create1");

    struct epoll_event event;
    event.events = EPOLLIN;
    event.data.fd = listen_fd;
    if (epoll_ctl(epoll_fd, EPOLL_CTL_ADD, listen_fd, &event) == -1) perror("epoll_ctl");

    struct epoll_event events[MAX_EVENTS];

    while (1) {
        int n = epoll_wait(epoll_fd, events, MAX_EVENTS, -1);
        if (n == -1) perror("epoll_wait");

        for (int i = 0; i < n; i++) {
            if (events[i].data.fd == listen_fd) {
                while (1) {
                    struct sockaddr_in client_addr;
                    socklen_t client_len = sizeof(client_addr);
                    int conn_fd = accept(listen_fd, (struct sockaddr*)&client_addr, &client_len);
                    if (conn_fd == -1) {
                        if (errno == EAGAIN || errno == EWOULDBLOCK) break;
                        else perror("accept");
                        continue;
                    }
                    set_nonblocking(conn_fd);
                    event.events = EPOLLIN | EPOLLET;
                    event.data.fd = conn_fd;
                    if (epoll_ctl(epoll_fd, EPOLL_CTL_ADD, conn_fd, &event) == -1) perror("epoll_ctl");
                }
            } else {
                char buf[1024];
                int conn_fd = events[i].data.fd;
                while (1) {
                    ssize_t count = read(conn_fd, buf, sizeof(buf));
                    if (count == -1) {
                        if (errno == EAGAIN || errno == EWOULDBLOCK) break;
                        else perror("read");
                        close(conn_fd);
                        break;
                    } else if (count == 0) {
                        close(conn_fd);
                        break;
                    }
                    write(conn_fd, buf, count);  // Echo back
                }
            }
        }
    }

    close(listen_fd);
    close(epoll_fd);
    return 0;
}