c语言epoll 客户端代码

C语言中使用epoll机制编写客户端代码如下：

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

#define MAX_EVENTS 100
#define MAX_BUF_SIZE 1024

int main(int argc, char** argv) {
    int sockfd, epollfd;
    struct epoll_event event, events[MAX_EVENTS];

    // 创建socket
    if ((sockfd = socket(AF_INET, SOCK_STREAM, 0)) < 0) {
        perror("socket creation failed");
        exit(EXIT_FAILURE);
    }

    // 设置服务器地址
    struct sockaddr_in server_addr;
    memset(&server_addr, 0, sizeof(server_addr));
    server_addr.sin_family = AF_INET;
    server_addr.sin_port = htons(8080);
    if (inet_pton(AF_INET, "127.0.0.1", &(server_addr.sin_addr)) <= 0) {
        perror("invalid address");
        exit(EXIT_FAILURE);
    }

    // 连接服务器
    if (connect(sockfd, (struct sockaddr*)&server_addr, sizeof(server_addr)) < 0) {
        perror("connection failed");
        exit(EXIT_FAILURE);
    }

    // 创建epoll实例
    if ((epollfd = epoll_create1(0)) < 0) {
        perror("epoll creation failed");
        exit(EXIT_FAILURE);
    }

    // 设置监听事件
    event.events = EPOLLIN;
    event.data.fd = sockfd;
    if (epoll_ctl(epollfd, EPOLL_CTL_ADD, sockfd, &event) < 0) {
        perror("epoll control failed");
        exit(EXIT_FAILURE);
    }

    char buf[MAX_BUF_SIZE];
    while (1) {
        int num_events = epoll_wait(epollfd, events, MAX_EVENTS, -1);
        for (int i = 0; i < num_events; i++) {
            if (events[i].data.fd == sockfd) {
                // 从服务器接收数据
                memset(buf, 0, sizeof(buf));
                ssize_t recv_len = recv(sockfd, buf, sizeof(buf), 0);
                if (recv_len < 0) {
                    perror("receive data failed");
                    exit(EXIT_FAILURE);
                } else if (recv_len == 0) {
                    printf("Connection closed by server\n");
                    exit(EXIT_SUCCESS);
                } else {
                    printf("Received message from server: %s", buf);
                }
            }
        }
    }

    close(sockfd);
    close(epollfd);
    return 0;
}

以上代码实现了一个简单的epoll客户端，将连接到服务器的socket加入到epoll事件中进行监听。当有事件触发时，通过recv函数接收服务器发送的数据，并打印到控制台上。同时，代码还对错误情况进行了处理，比如socket创建失败、连接失败等。