--- In firebird-support@yahoogroups.com, "Dan Cooperstock" <dcoops@...>
wrote:

>
>
> That idea is fairly similar to the idea someone on an ASP
> (Association of Shareware Professionals) forum suggested, which is to
> send out a multicast UDP packet on startup, that other instances of
> my program on the same subnet respond to with "Yes, I'm here". The
> sender counts the responses, and if they exceed the licensed # of
> users (minus one, to allow the sender to run), prevents the sender
> from running.
>
> This actually seems a bit simpler, because it doesn't need a server
> program, and isn't affected by crashes.
>
> Any comments on that idea? Thanks.
>

Remember that UDP is unreliable if you need all of the other instances
to answer, since it is a send-and-forget protocol. No control is done
at UDP protocol level to assure all instances have answered.

That is no big problem if you know who should be online, but it would
be in your case IMHO. Personally I would go for a solution like Lee
proposes.

Regards,

Guillem