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 1 /**
 2   @lib libevent
 3   @file listener.h
 4   @function evconnlistener_new_bind()
 5 */
 6 
 7 /**
 8    Allocate a new evconnlistener object to listen for incoming TCP connections
 9    on a given address.
10 
11    @param base The event base to associate the listener with.
12    @param cb A callback to be invoked when a new connection arrives. If the
13       callback is NULL, the listener will be treated as disabled until the
14       callback is set.
15    @param ptr A user-supplied pointer to give to the callback.
16    @param flags Any number of LEV_OPT_* flags
17    @param backlog Passed to the listen() call to determine the length of the
18       acceptable connection backlog.  Set to -1 for a reasonable default.
19    @param addr The address to listen for connections on.
20    @param socklen The length of the address.
21  */
22 struct evconnlistener*
23     evconnlistener_new_bind(
24         struct event_base *base,
25         evconnlistener_cb cb, 
26         void *ptr, 
27         unsigned flags, 
28         int backlog,
29         const struct sockaddr *sa, 
30         int socklen);
31    
32 /**
33    A callback that we invoke when a listener has a new connection.
34 
35    @param listener The evconnlistener
36    @param fd The new file descriptor
37    @param addr The source address of the connection
38    @param socklen The length of addr
39    @param user_arg the pointer passed to evconnlistener_new()
40  */
41 typedef void (*evconnlistener_cb)(
42     struct evconnlistener *, 
43     evutil_socket_t, 
44     struct sockaddr *, 
45     int socklen, 
46     void *); 

/**
  event_driven.c
*/
#include <stdio.h>
#include <strings.h>
#include <event2/listener.h>
#include <event2/bufferevent.h>
#include <event2/buffer.h>
#include <arpa/inet.h>

#define PORT 8111

void on_read_cb(struct bufferevent* bev, void* ctx)
{
    struct evbuffer* input = NULL;
    struct evbuffer* output = NULL;
    input = bufferevent_get_input(bev);
    output = bufferevent_get_output(bev);
    evbuffer_add_buffer(output, input);
}

void on_accept_cb(struct evconnlistener* listener,
                  evutil_socket_t fd,
                  struct sockaddr* addr,
                  int socklen,
                  void* ctx)
{
    printf("connection[%d] accepted\n", fd);
    struct event_base* base = NULL;
    struct bufferevent* bev = NULL;

    base = evconnlistener_get_base(listener);    
    bev = bufferevent_socket_new(base, fd, 0);

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

int main(int argc, char* argv[])
{
    struct sockaddr_in serv_addr;
    struct event_base* base = NULL;
    struct evconnlistener* listener = NULL;
    base = event_base_new();

    bzero(&serv_addr, sizeof(serv_addr));
    serv_addr.sin_family = AF_INET;
    serv_addr.sin_port = htons(PORT);
    serv_addr.sin_addr.s_addr = htonl(INADDR_ANY);
    listener = evconnlistener_new_bind(
                            base,
                            on_accept_cb,
                            NULL,
                            LEV_OPT_REUSEABLE,
                            10,
                            (struct sockaddr *)&serv_addr,
                            sizeof(serv_addr));
    if (listener != NULL) {
        printf("listening on port[%d]\n", PORT);
    }

    event_base_dispatch(base);

    return 0;
}

# gcc -std=c11 -g -o event_driven event_driven.c `pkg-config --libs --cflags libevent`
# ./event_driven