C：epoll和多线程

使用C语言进行网络编程时，我们经常会遇到需要同时处理多个客户端连接的情况。为了高效地处理大量的并发连接，我们可以使用epoll和多线程的技术。本文将介绍epoll和多线程的原理，并提供一个案例代码，帮助读者更好地理解和应用这些技术。

c
#include 
#include 
#include 
#include 
#define MAX_EVENTS 10
int main() {
    int epoll_fd, num_ready;
    struct epoll_event events[MAX_EVENTS];
    // 创建epoll实例
    epoll_fd = epoll_create1(0);
    if (epoll_fd == -1) {
        perror("epoll_create1");
        exit(EXIT_FAILURE);
    }
    // 添加需要监视的文件描述符
    struct epoll_event event;
    event.events = EPOLLIN;
    event.data.fd = STDIN_FILENO;
    if (epoll_ctl(epoll_fd, EPOLL_CTL_ADD, STDIN_FILENO, &event) == -1) {
        perror("epoll_ctl");
        exit(EXIT_FAILURE);
    }
    // 等待文件描述符就绪
    num_ready = epoll_wait(epoll_fd, events, MAX_EVENTS, -1);
    if (num_ready == -1) {
        perror("epoll_wait");
        exit(EXIT_FAILURE);
    }
    // 处理就绪的文件描述符
    for (int i = 0; i < num_ready; i++) {
        if (events[i].data.fd == STDIN_FILENO) {
            char buf[256];
            int num_read = read(STDIN_FILENO, buf, sizeof(buf));
            if (num_read == -1) {
                perror("read");
                exit(EXIT_FAILURE);
            }
            printf("Read %d bytes: %.*s\n", num_read, num_read, buf);
        }
    }
    close(epoll_fd);
    return 0;
}

c
#include 
#include 
#include 
#include 
#define NUM_THREADS 5
void* thread_function(void* arg) {
    int thread_id = *(int*)arg;
    printf("Thread %d is running\n", thread_id);
    
    // 线程具体的处理逻辑
    sleep(1);
    
    printf("Thread %d is exiting\n", thread_id);
    pthread_exit(NULL);
}
int main() {
    pthread_t threads[NUM_THREADS];
    int thread_ids[NUM_THREADS];
    // 创建多个线程
    for (int i = 0; i < NUM_THREADS; i++) {
        thread_ids[i] = i;
        if (pthread_create(&threads[i], NULL, thread_function, &thread_ids[i]) != 0) {
            perror("pthread_create");
            exit(EXIT_FAILURE);
        }
    }
    // 等待所有线程结束
    for (int i = 0; i < NUM_THREADS; i++) {
        if (pthread_join(threads[i], NULL) != 0) {
            perror("pthread_join");
            exit(EXIT_FAILURE);
        }
    }
    return 0;
}

c
#include 
#include 
#include 
#include 
#include 
#define MAX_EVENTS 10
#define NUM_THREADS 5
void* thread_function(void* arg) {
    int client_fd = *(int*)arg;
    printf("Thread handling client %d is running\n", client_fd);
    // 线程具体的处理逻辑
    sleep(1);
    printf("Thread handling client %d is exiting\n", client_fd);
    close(client_fd);
    pthread_exit(NULL);
}
int main() {
    int epoll_fd, num_ready;
    struct epoll_event events[MAX_EVENTS];
    pthread_t threads[NUM_THREADS];
    // 创建epoll实例
    epoll_fd = epoll_create1(0);
    if (epoll_fd == -1) {
        perror("epoll_create1");
        exit(EXIT_FAILURE);
    }
    // 添加需要监视的文件描述符
    // 此处省略了添加监听套接字的代码
    // 等待文件描述符就绪
    num_ready = epoll_wait(epoll_fd, events, MAX_EVENTS, -1);
    if (num_ready == -1) {
        perror("epoll_wait");
        exit(EXIT_FAILURE);
    }
    // 处理就绪的文件描述符
    for (int i = 0; i < num_ready; i++) {
        if (events[i].events & EPOLLIN) {
            // 创建一个新线程来处理连接
            int client_fd = events[i].data.fd;
            if (pthread_create(&threads[i % NUM_THREADS], NULL, thread_function, &client_fd) != 0) {
                perror("pthread_create");
                exit(EXIT_FAILURE);
            }
        }
    }
    // 等待所有线程结束
    for (int i = 0; i < NUM_THREADS; i++) {
        if (pthread_join(threads[i], NULL) != 0) {
            perror("pthread_join");
            exit(EXIT_FAILURE);
        }
    }
    close(epoll_fd);
    return 0;
}