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/* 创建监听器（已绑定socket）
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 * @param base     event_base
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 * @param cb       接受连接的回调函数
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 * @param ptr      回调函数的参数
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 * @param flags    选项标志
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 * @param backlog  listen()的backlog参数，-1表示使用默认值
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 * @param sa       绑定的地址
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 * @param socklen  地址长度
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 */
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struct evconnlistener *evconnlistener_new_bind(struct event_base *base,
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    evconnlistener_cb cb, void *ptr, unsigned flags, int backlog,
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    const struct sockaddr *sa, int socklen);
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/* 创建监听器（已有socket）
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 * @param fd       已绑定的socket
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 */
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struct evconnlistener *evconnlistener_new(struct event_base *base,
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    evconnlistener_cb cb, void *ptr, unsigned flags, int backlog,
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    evutil_socket_t fd);
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/* 释放监听器 */
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void evconnlistener_free(struct evconnlistener *lev);

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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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#include <signal.h>
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#include <event2/buffer.h>
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#include <event2/bufferevent.h>
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#include <event2/listener.h>
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#include <event2/event.h>
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static const int PORT = 8080;
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static void echo_read_cb(struct bufferevent *bev, void *ctx) {
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    struct evbuffer *input = bufferevent_get_input(bev);
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    struct evbuffer *output = bufferevent_get_output(bev);
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    evbuffer_add_buffer(output, input);
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}
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static void echo_event_cb(struct bufferevent *bev, short events, void *ctx) {
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    if (events & BEV_EVENT_ERROR) {
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        perror("Error from bufferevent");
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    }
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    if (events & (BEV_EVENT_EOF | BEV_EVENT_ERROR)) {
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        bufferevent_free(bev);
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    }
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}
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static void accept_conn_cb(struct evconnlistener *listener,
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    evutil_socket_t fd, struct sockaddr *address, int socklen, void *ctx) {
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    printf("New connection: fd=%d\n", fd);
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    struct event_base *base = evconnlistener_get_base(listener);
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    struct bufferevent *bev = bufferevent_socket_new(base, fd, BEV_OPT_CLOSE_ON_FREE);
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    bufferevent_setcb(bev, echo_read_cb, NULL, echo_event_cb, NULL);
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    bufferevent_enable(bev, EV_READ | EV_WRITE);
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}
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static void accept_error_cb(struct evconnlistener *listener, void *ctx) {
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    struct event_base *base = evconnlistener_get_base(listener);
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    int err = EVUTIL_SOCKET_ERROR();
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    fprintf(stderr, "Got an error %d (%s) on the listener. Shutting down.\n",
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            err, evutil_socket_error_to_string(err));
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    event_base_loopexit(base, NULL);
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}
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static void signal_cb(evutil_socket_t sig, short events, void *user_data) {
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    struct event_base *base = user_data;
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    printf("Caught signal %d, shutting down.\n", sig);
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    event_base_loopexit(base, NULL);
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}
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int main(int argc, char **argv) {
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    struct event_base *base;
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    struct evconnlistener *listener;
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    struct event *signal_event;
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    struct sockaddr_in sin;
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    base = event_base_new();
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    if (!base) {
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        fprintf(stderr, "Could not initialize libevent!\n");
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        return 1;
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    }
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    memset(&sin, 0, sizeof(sin));
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    sin.sin_family = AF_INET;
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    sin.sin_port = htons(PORT);
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    sin.sin_addr.s_addr = htonl(INADDR_ANY);
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    listener = evconnlistener_new_bind(base, accept_conn_cb, NULL,
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        LEV_OPT_REUSEABLE | LEV_OPT_CLOSE_ON_FREE, -1,
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        (struct sockaddr*)&sin, sizeof(sin));
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    if (!listener) {
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        fprintf(stderr, "Could not create a listener!\n");
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        return 1;
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    }
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    evconnlistener_set_error_cb(listener, accept_error_cb);
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    signal_event = evsignal_new(base, SIGINT, signal_cb, (void*)base);
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    if (!signal_event || event_add(signal_event, NULL) < 0) {
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        fprintf(stderr, "Could not create/add a signal event!\n");
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        return 1;
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    }
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    printf("Server listening on port %d\n", PORT);
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    event_base_dispatch(base);
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    evconnlistener_free(listener);
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    event_free(signal_event);
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    event_base_free(base);
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    printf("Server shutdown complete\n");
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    return 0;
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}