面试题：C语言epoll机制的应用实现

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <sys/socket.h>
#include <sys/epoll.h>

#define MAX_EVENTS 10
#define BUFFER_SIZE 1024

int main() {
    int server_fd, client_fd;
    struct sockaddr_in server_addr, client_addr;
    socklen_t client_addr_len = sizeof(client_addr);

    // 创建套接字
    server_fd = socket(AF_INET, SOCK_STREAM, 0);
    if (server_fd == -1) {
        perror("socket creation failed");
        exit(EXIT_FAILURE);
    }

    // 配置服务器地址
    server_addr.sin_family = AF_INET;
    server_addr.sin_port = htons(8080);
    server_addr.sin_addr.s_addr = INADDR_ANY;

    // 绑定套接字到地址
    if (bind(server_fd, (struct sockaddr *)&server_addr, sizeof(server_addr)) == -1) {
        perror("bind failed");
        close(server_fd);
        exit(EXIT_FAILURE);
    }

    // 监听连接
    if (listen(server_fd, 5) == -1) {
        perror("listen failed");
        close(server_fd);
        exit(EXIT_FAILURE);
    }

    int epoll_fd = epoll_create1(0);
    if (epoll_fd == -1) {
        perror("epoll_create1 failed");
        close(server_fd);
        exit(EXIT_FAILURE);
    }

    struct epoll_event event;
    event.data.fd = server_fd;
    event.events = EPOLLIN;
    if (epoll_ctl(epoll_fd, EPOLL_CTL_ADD, server_fd, &event) == -1) {
        perror("epoll_ctl add server_fd failed");
        close(server_fd);
        close(epoll_fd);
        exit(EXIT_FAILURE);
    }

    struct epoll_event events[MAX_EVENTS];
    char buffer[BUFFER_SIZE];

    while (1) {
        int num_events = epoll_wait(epoll_fd, events, MAX_EVENTS, -1);
        if (num_events == -1) {
            perror("epoll_wait failed");
            break;
        }

        for (int i = 0; i < num_events; ++i) {
            if (events[i].data.fd == server_fd) {
                // 处理新的连接
                client_fd = accept(server_fd, (struct sockaddr *)&client_addr, &client_addr_len);
                if (client_fd == -1) {
                    perror("accept failed");
                    continue;
                }

                event.data.fd = client_fd;
                event.events = EPOLLIN;
                if (epoll_ctl(epoll_fd, EPOLL_CTL_ADD, client_fd, &event) == -1) {
                    perror("epoll_ctl add client_fd failed");
                    close(client_fd);
                }
            } else {
                // 处理客户端消息
                client_fd = events[i].data.fd;
                ssize_t bytes_read = recv(client_fd, buffer, sizeof(buffer), 0);
                if (bytes_read <= 0) {
                    if (bytes_read == 0) {
                        // 客户端关闭连接
                        printf("Client disconnected\n");
                    } else {
                        perror("recv failed");
                    }
                    epoll_ctl(epoll_fd, EPOLL_CTL_DEL, client_fd, NULL);
                    close(client_fd);
                } else {
                    // 回显消息给客户端
                    send(client_fd, buffer, bytes_read, 0);
                }
            }
        }
    }

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