[Libevent-users] Simple client. How to handle login prompts.

[Øystein Schønning-Johansen]

Hi!

I'm trying to connect a bot to a server called FIBS. First Internet
Backgammon Server. (www.fibs.com) The server is really simple with a plain
connection. Try it yourself: telnet fibs.com 4321

After some browsing (and failures), I found out that I need an event
handling mechanism and buffered input and output. After some more googling,
I found that libevent provides all these features.

However, I'm struggling. I can't find examples nor tutorials to help me.
And my experience with events and socket programming is limited.

Here is my current skeleton code:
/*
 * A simple event driven code for connecting to FIBS. (First Internet
Backgammon Server.)
 * More info of fibs: www.fibs.com
 */
#include <event2/dns.h>
#include <event2/bufferevent.h>
#include <event2/buffer.h>
#include <event2/util.h>
#include <event2/event.h>

#include <stdio.h>
#include <stdlib.h>

void handler (struct evbuffer *buffer, const struct evbuffer_cb_info *info,
void *arg)
{
#if 1
    char buf[1024];
    int n;
    while ((n = evbuffer_remove(buffer, buf, sizeof(buf))) > 0) {
/* handle the message form the server */
        printf( buf );
    }
#else
    size_t len;
    printf(" * ");
    char *request_line;
    request_line = evbuffer_readln(buffer, &len, EVBUFFER_EOL_CRLF);
    if (!request_line) {
    //    printf("No line.\n");
        /* The first line has not arrived yet. */
    } else {
        printf("%s\n", request_line);
        free(request_line);
    }
#endif
}

void readcb(struct bufferevent *bev, void *ptr)
{
    printf("Read callback.\n");
}

void writecb(struct bufferevent *bev, void *ptr)
{
    printf("Write callback.\n");
}

/* Code taken from http example */
void eventcb(struct bufferevent *bev, short events, void *ptr)
{
    if (events & BEV_EVENT_CONNECTED) {
         printf("Connect okay.\n");
    } else if (events & (BEV_EVENT_ERROR|BEV_EVENT_EOF)) {
         struct event_base *base = ptr;
         if (events & BEV_EVENT_ERROR) {
                 int err = bufferevent_socket_get_dns_error(bev);
                 if (err)
                         printf("DNS error: %s\n",
evutil_gai_strerror(err));
         }
         printf("Closing\n");
         bufferevent_free(bev);
         event_base_loopexit(base, NULL);
    }
}

#define FIBS_HOST "fibs.com"
#define FIBS_PORT 4321

int main(int argc, char **argv)
{
    struct event_base *base;
    struct evdns_base *dns_base;
    struct bufferevent *bev;

    base = event_base_new();
    dns_base = evdns_base_new(base, 1);

    bev = bufferevent_socket_new(base, -1, BEV_OPT_CLOSE_ON_FREE);
    bufferevent_setcb(bev, readcb, writecb, eventcb, base);
    bufferevent_enable(bev, EV_READ|EV_WRITE);
    bufferevent_socket_connect_hostname( bev, dns_base, AF_UNSPEC,
FIBS_HOST, FIBS_PORT);

    /* Add callback to the evbuffer. (input buffer) */
    struct evbuffer *input = bufferevent_get_input(bev);
    evbuffer_add_cb( input, handler, NULL );

    event_base_dispatch(base);
    return 0;
}

Here comes all my questions:
* Am I on the right track?
* The login prompt from the server does not send a newline, so the handle
is not called. How can I find the login prompt?
* I also try to read the lines in the handle callback evbuffer_readln(),
but the lines will then bre printed in the wrong order. Why?

Thanks for any input?
-Øystein