[avahi] Publish service and service discovery with one poll loop

Alin Rus netblock at gmail.com
Sun May 27 14:13:14 PDT 2012


I'm considering using Avahi for a project targeting embedded Linux.
Basically what I'm trying to do is publish a service from my
application and from the same application discover other nodes that
have published the same service over the LAN.

As far as I know I can get away with only using libavahi-core,
libavahi-daemon and libdaemon. There won't be an Avahi service running
on that platform.

I was looking at core-browse-services.c and core-publish-services.c
and here are a couple of questions:

1)  Is it possible to bypass the poll loop for service discovery and
just get the hosts whenever I need?

2) While looking at the examples is not clear to me whether is
possible to publish a service and do service discovery from the same
app. I compiled core-browse-services and core-publish-services and I
get the following warning

*** WARNING: Detected another IPv4 mDNS stack running on this host.
This makes mDNS unreliable and is thus not recommended. ***

3) Would this be a valid solution for publishing and discovering
services from the same app?

  if (!(simple_poll = avahi_simple_poll_new())) {
        fprintf(stderr, "Failed to create simple poll object.\n");
        goto fail;

    name = avahi_strdup("SOME_SERVICE");

    /* Let's set the host name for this server. */
    config.publish_hinfo = 0;
    config.publish_addresses = 0;
    config.host_name = avahi_strdup("my_host");
    config.publish_workstation = 0;
    config.publish_domain = 0;

    /* Allocate a new server */
    server = avahi_server_new(avahi_simple_poll_get(simple_poll),
&config, server_callback, NULL, &error);

    /* Free the configuration data */
    /* Check wether creating the server object succeeded */
    if (!server) {
        fprintf(stderr, "Failed to create server: %s\n", avahi_strerror(error));
        goto fail;

    /* Create the service browser */
    if (!(sb = avahi_s_service_browser_new(server, AVAHI_IF_UNSPEC,
AVAHI_PROTO_UNSPEC, "_http._tcp", NULL, 0, browse_callback, server)))
        fprintf(stderr, "Failed to create service browser: %s\n",
        goto fail;

    /* Run the main loop */

Basically I've combined the two examples.


Alin Rus
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