libevent高并发服务器

libevent是一个事件驱动的网络库，它可以帮助开发者快速构建高并发服务器。它的核心是基于事件的回调机制，当一个网络事件发生时，libevent会调用相应的回调函数进行处理。在高并发的情况下，libevent可以通过多路复用技术一次性处理多个连接，从而提高服务器的性能和可扩展性。此外，libevent还提供了对定时器、信号等事件的处理，使得开发者可以方便地进行事件驱动的编程。

相关问题

libevent 高并发http服务器代码

下面是一个基于libevent的高并发HTTP服务器的代码示例：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <event.h>

#define SERVER_PORT 8080
#define MAX_CLIENTS 64

void on_accept(int fd, short event, void *arg) {
    int client_fd = accept(fd, NULL, NULL);
    if (client_fd < 0) {
        perror("accept");
        return;
    }

    printf("Accepted connection from client %d\n", client_fd);

    struct event_base *base = (struct event_base *)arg;
    struct bufferevent *bev = bufferevent_socket_new(base, client_fd, BEV_OPT_CLOSE_ON_FREE);

    bufferevent_setcb(bev, NULL, NULL, NULL, NULL);
    bufferevent_enable(bev, EV_READ | EV_WRITE);
}

void on_request(struct bufferevent *bev, void *arg) {
    char buffer[1024];
    int n;
    while ((n = bufferevent_read(bev, buffer, sizeof(buffer))) > 0) {
        printf("Received %d bytes from client %d\n", n, bufferevent_getfd(bev));
        bufferevent_write(bev, buffer, n);
    }
}

int main(int argc, char *argv[]) {
    int server_fd = socket(AF_INET, SOCK_STREAM, 0);
    if (server_fd < 0) {
        perror("socket");
        exit(1);
    }

    struct sockaddr_in server_addr = {0};
    server_addr.sin_family = AF_INET;
    server_addr.sin_addr.s_addr = htonl(INADDR_ANY);
    server_addr.sin_port = htons(SERVER_PORT);

    if (bind(server_fd, (struct sockaddr *)&server_addr, sizeof(server_addr)) < 0) {
        perror("bind");
        exit(1);
    }

    if (listen(server_fd, MAX_CLIENTS) < 0) {
        perror("listen");
        exit(1);
    }

    printf("Server is listening on port %d\n", SERVER_PORT);

    struct event_base *base = event_base_new();
    struct event *server_event = event_new(base, server_fd, EV_READ | EV_PERSIST, on_accept, base);
    event_add(server_event, NULL);

    event_base_dispatch(base);

    return 0;
}

这个程序使用了libevent库来实现一个简单的高并发HTTP服务器，它可以同时处理多个客户端连接。当有新的客户端连接时，服务器会使用bufferevent_socket_new函数创建一个新的bufferevent来处理该连接。当客户端发送数据时，服务器会使用bufferevent_read函数来读取数据，并使用bufferevent_write函数将数据发送回客户端。

c语言 libevent高并发代码

下面是一个使用 libevent 实现高并发的 C 语言代码示例：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <event2/event.h>

void on_accept(int fd, short event, void *arg);
void on_read(int fd, short event, void *arg);
void on_write(int fd, short event, void *arg);

int main(int argc, char **argv) {
    struct event_base *base;
    struct event *listener_event;
    struct sockaddr_in sin;
    int listener_fd;
    int reuseaddr_on = 1;

    memset(&sin, 0, sizeof(sin));
    sin.sin_family = AF_INET;
    sin.sin_addr.s_addr = INADDR_ANY;
    sin.sin_port = htons(8080);

    base = event_base_new();
    if (!base) {
        printf("Error: could not initialize libevent!\n");
        return EXIT_FAILURE;
    }

    listener_fd = socket(AF_INET, SOCK_STREAM, 0);
    if (listener_fd < 0) {
        printf("Error: could not create socket!\n");
        return EXIT_FAILURE;
    }

    if (setsockopt(listener_fd, SOL_SOCKET, SO_REUSEADDR, &reuseaddr_on, sizeof(reuseaddr_on)) == -1) {
        printf("Error: could not set SO_REUSEADDR!\n");
        return EXIT_FAILURE;
    }

    if (bind(listener_fd, (struct sockaddr *)&sin, sizeof(sin)) < 0) {
        printf("Error: could not bind socket!\n");
        return EXIT_FAILURE;
    }

    if (listen(listener_fd, SOMAXCONN) < 0) {
        printf("Error: could not listen on socket!\n");
        return EXIT_FAILURE;
    }

    listener_event = event_new(base, listener_fd, EV_READ | EV_PERSIST, on_accept, (void *)base);
    event_add(listener_event, NULL);

    event_base_dispatch(base);

    return EXIT_SUCCESS;
}

void on_accept(int fd, short event, void *arg) {
    struct event_base *base = (struct event_base *)arg;
    struct sockaddr_in sin;
    socklen_t slen = sizeof(sin);
    int client_fd;
    struct event *client_event;

    client_fd = accept(fd, (struct sockaddr *)&sin, &slen);
    if (client_fd < 0) {
        printf("Error: could not accept connection!\n");
        return;
    }

    printf("Accepted connection from %s:%d\n", inet_ntoa(sin.sin_addr), ntohs(sin.sin_port));

    client_event = event_new(base, client_fd, EV_READ | EV_PERSIST, on_read, NULL);
    event_add(client_event, NULL);
}

void on_read(int fd, short event, void *arg) {
    char buffer[1024];
    int nread;

    nread = recv(fd, buffer, sizeof(buffer), 0);
    if (nread < 0) {
        printf("Error: could not read from socket!\n");
        return;
    }

    if (nread == 0) {
        printf("Closing connection...\n");
        close(fd);
        event_del((struct event *)arg);
        event_free((struct event *)arg);
        return;
    }

    printf("Received %d bytes: %.*s\n", nread, nread, buffer);

    struct event *write_event = event_new((struct event_base *)arg, fd, EV_WRITE, on_write, NULL);
    event_add(write_event, NULL);
}

void on_write(int fd, short event, void *arg) {
    const char *response = "HTTP/1.1 200 OK\r\nContent-Length: 19\r\n\r\nHello, World!\r\n";
    int nwritten;

    nwritten = send(fd, response, strlen(response), 0);
    if (nwritten < 0) {
        printf("Error: could not write to socket!\n");
        return;
    }

    printf("Sent %d bytes: %s", nwritten, response);

    close(fd);
    event_del((struct event *)arg);
    event_free((struct event *)arg);
}

这个示例程序创建了一个基于 libevent 的 TCP 服务器，它监听端口 8080，并使用 `on_accept` 回调函数处理新连接。当有新的客户端连接时，该程序会创建一个新的事件，使用 `on_read` 回调函数处理该客户端的读事件。当客户端有数据可读时，该程序会读取数据并使用 `on_write` 回调函数发送响应。注意，这个简单的示例程序没有进行任何请求解析和错误处理，仅仅是一个简单的回显服务器。