C语言 epoll 客户端和服务端

下面是使用 C 语言实现 epoll 的客户端和服务端代码示例。

服务端代码：

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

#define MAX_EVENTS 10
#define BUF_SIZE 256

int main(int argc, char* argv[])
{
    int port = atoi(argv[1]); // 获取端口号

    int server_fd = socket(AF_INET, SOCK_STREAM, 0);
    if (server_fd < 0) {
        perror("socket() failed");
        exit(EXIT_FAILURE);
    }

    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(server_fd, (struct sockaddr*)&server_addr, sizeof(server_addr)) < 0) {
        perror("bind() failed");
        exit(EXIT_FAILURE);
    }

    if (listen(server_fd, 10) < 0) {
        perror("listen() failed");
        exit(EXIT_FAILURE);
    }

    printf("Listening on port %d...\n", port);

    int epoll_fd = epoll_create1(0);
    if (epoll_fd < 0) {
        perror("epoll_create1() failed");
        exit(EXIT_FAILURE);
    }

    struct epoll_event event, events[MAX_EVENTS];
    event.data.fd = server_fd;
    event.events = EPOLLIN;
    if (epoll_ctl(epoll_fd, EPOLL_CTL_ADD, server_fd, &event) < 0) {
        perror("epoll_ctl() failed");
        exit(EXIT_FAILURE);
    }

    char buf[BUF_SIZE];
    while (1) {
        int ready = epoll_wait(epoll_fd, events, MAX_EVENTS, -1);
        if (ready < 0) {
            perror("epoll_wait() failed");
            exit(EXIT_FAILURE);
        }

        for (int i = 0; i < ready; i++) {
            if (events[i].data.fd == server_fd) {
                struct sockaddr_in client_addr;
                socklen_t client_len = sizeof(client_addr);
                int client_fd = accept(server_fd, (struct sockaddr*)&client_addr, &client_len);
                if (client_fd < 0) {
                    perror("accept() failed");
                    exit(EXIT_FAILURE);
                }
                printf("Client connected: %s:%d\n", inet_ntoa(client_addr.sin_addr), ntohs(client_addr.sin_port));

                event.data.fd = client_fd;
                event.events = EPOLLIN;
                if (epoll_ctl(epoll_fd, EPOLL_CTL_ADD, client_fd, &event) < 0) {
                    perror("epoll_ctl() failed");
                    exit(EXIT_FAILURE);
                }
            } else {
                int client_fd = events[i].data.fd;
                ssize_t count = recv(client_fd, buf, sizeof(buf), 0);
                if (count < 0) {
                    perror("recv() failed");
                    exit(EXIT_FAILURE);
                } else if (count == 0) {
                    printf("Client disconnected\n");
                    close(client_fd);
                } else {
                    printf("Received %ld bytes from client: %.*s\n", count, (int)count, buf);
                    send(client_fd, buf, count, 0);
                }
            }
        }
    }

    close(server_fd);
    return 0;
}

客户端代码：

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

#define MAX_EVENTS 10
#define BUF_SIZE 256

int main(int argc, char* argv[])
{
    const char* server_ip = argv[1];
    int port = atoi(argv[2]);

    int client_fd = socket(AF_INET, SOCK_STREAM, 0);
    if (client_fd < 0) {
        perror("socket() failed");
        exit(EXIT_FAILURE);
    }

    struct sockaddr_in server_addr;
    memset(&server_addr, 0, sizeof(server_addr));
    server_addr.sin_family = AF_INET;
    server_addr.sin_addr.s_addr = inet_addr(server_ip);
    server_addr.sin_port = htons(port);

    if (connect(client_fd, (struct sockaddr*)&server_addr, sizeof(server_addr)) < 0) {
        perror("connect() failed");
        exit(EXIT_FAILURE);
    }

    printf("Connected to server: %s:%d\n", server_ip, port);

    int epoll_fd = epoll_create1(0);
    if (epoll_fd < 0) {
        perror("epoll_create1() failed");
        exit(EXIT_FAILURE);
    }

    struct epoll_event event, events[MAX_EVENTS];
    event.data.fd = client_fd;
    event.events = EPOLLIN;
    if (epoll_ctl(epoll_fd, EPOLL_CTL_ADD, client_fd, &event) < 0) {
        perror("epoll_ctl() failed");
        exit(EXIT_FAILURE);
    }

    char buf[BUF_SIZE];
    while (1) {
        int ready = epoll_wait(epoll_fd, events, MAX_EVENTS, -1);
        if (ready < 0) {
            perror("epoll_wait() failed");
            exit(EXIT_FAILURE);
        }

        for (int i = 0; i < ready; i++) {
            if (events[i].data.fd == client_fd) {
                ssize_t count = recv(client_fd, buf, sizeof(buf), 0);
                if (count < 0) {
                    perror("recv() failed");
                    exit(EXIT_FAILURE);
                } else if (count == 0) {
                    printf("Server disconnected\n");
                    close(client_fd);
                } else {
                    printf("Received %ld bytes from server: %.*s\n", count, (int)count, buf);
                }
            } else {
                fgets(buf, sizeof(buf), stdin);
                ssize_t count = send(client_fd, buf, strlen(buf), 0);
                if (count < 0) {
                    perror("send() failed");
                    exit(EXIT_FAILURE);
                }
            }
        }
    }

    close(client_fd);
    return 0;
}

在这个示例中，我们使用了 epoll 来实现并发处理多个客户端的连接。服务器会等待客户端连接，一旦有客户端连接，就将其加入 epoll 等待队列中。同时，客户端也会连接服务器，并将其套接字加入 epoll 等待队列中。当客户端或服务器有消息到来时，都会触发 epoll_wait() 函数。然后，我们可以使用 recv() 和 send() 函数来接收和发送消息。

请注意，这只是一个示例代码，可能还需要进行更多的错误处理和安全检查。