tcp-non-blocking-libevent-echo-server.c

#include <fcntl.h>
#include <netinet/in.h>
#include <sys/socket.h>

#include <event2/buffer.h>
#include <event2/bufferevent.h>
#include <event2/event.h>

#include <assert.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#define MAX_LINE 16384

void on_read(struct bufferevent *bev, void *ctx)
{
    struct evbuffer *input = bufferevent_get_input(bev);
    struct evbuffer *output = bufferevent_get_output(bev);

    char *line;
    size_t n;

    while ((line = evbuffer_readln(input, &n, EVBUFFER_EOL_LF)))
    {
        evbuffer_add(output, line, n);
        evbuffer_add(output, "\n", 1);
        free(line);
    }

    if (evbuffer_get_length(input) >= MAX_LINE)
    {
        /* line is too long */
        char buf[1024];
        while (evbuffer_get_length(input))
        {
            int n = evbuffer_remove(input, buf, sizeof(buf));
            evbuffer_add(output, buf, n);
        }
        evbuffer_add(output, "\n", 1);
    }
}

void on_error(struct bufferevent *bev, short error, void *ctx)
{
    if (error & BEV_EVENT_EOF)
    {
    }
    else if (error & BEV_EVENT_ERROR)
    {
    }
    else if (error & BEV_EVENT_TIMEOUT)
    {
    }
    bufferevent_free(bev);
}

void on_accept(evutil_socket_t listener, short event, void *arg)
{
    struct event_base *base = (struct event_base *)arg;
    struct sockaddr_storage ss;
    socklen_t slen = sizeof(ss);
    int fd = accept(listener, (struct sockaddr *)&ss, &slen);
    if (fd < 0)
    {
        perror("accept");
    }
    else if (fd > FD_SETSIZE)
    {
        close(fd);
    }
    else
    {
        evutil_make_socket_nonblocking(fd);
        struct bufferevent *bev = bufferevent_socket_new(base, fd, BEV_OPT_CLOSE_ON_FREE);
        bufferevent_setcb(bev, on_read, NULL, on_error, NULL);
        bufferevent_setwatermark(bev, EV_READ, 0, MAX_LINE);
        bufferevent_enable(bev, EV_READ | EV_WRITE);
    }
}

int main(int argc, char **argv)
{
    evutil_socket_t listener = socket(AF_INET, SOCK_STREAM, 0);
    evutil_make_socket_nonblocking(listener);

    struct sockaddr_in sin;
    sin.sin_family = AF_INET;
    sin.sin_addr.s_addr = 0;
    sin.sin_port = htons(40713);

    if (bind(listener, (struct sockaddr *)&sin, sizeof(sin)) < 0)
    {
        perror("bind");
        return 1;
    }

    if (listen(listener, 16) < 0)
    {
        perror("listen");
        return 1;
    }

    struct event_base *base = event_base_new();
    base = event_base_new();
    if (!base)
        return 1;

    struct event *listener_event = event_new(base, listener, EV_READ | EV_PERSIST, on_accept, (void *)base);
    event_add(listener_event, NULL);
    event_base_dispatch(base);

    return 0;
}