Hi Guillem,

> 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.

It is very reliable in local area networks which is what we're talking about
in this license checking. At least one commercial software protection system
implements a similar license checking technique using the mailslot protocol
instead of UDP. It's very similar in nature but gets through almost all
personal firewall software (such as ZoneAlarm, Norton Internet Security,
McAffee...) except for the Windows XP firewall (incoming side).

With any broadcast where all listeners respond it would be a good idea to
implement a random delay (say 0 to 1000ms) before responding. This increases
the reliability and need to retransmit.

We're getting off-topic though so I'll stop here.

Regards,
Jarrod Hollingworth

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