--- In firebird-support@yahoogroups.com, Lee Jenkins <lee@...> wrote:

> The problem is that your licensing might be fairly easily

circumvented through

> the database, IMO.
>
> I had a need to do what you're doing and simply created a TCP

based "License

> Manager" that runs as a service (or app depending on OS) on the

server or master

> computer. When workstations start the software, the software uses

encrypted

> communication to talk with the license manager to say

basically "hey, can I

> run?", the license manager says "well, only 4 out of 7 licenses are

being used

> so sure!". The used count get incremented. When workstations

shutdown the

> software, the software logs into the license manager again to "log

out" thereby

> freeing up another license.
>
> The license manager also tracks the IP of the workstation that gets

clearance to

> run so that if the workstation or license manager were to go down

for some

> reason, the license manager would read the IP of the incoming

request when

> restarted and determine that the workstation was already allowed to

run.

>
> All in all, works very well and I keep that logic out of the

database. Of

> course, a determined hacker/cracker would still be able to

circumvent the system

> with some work which I know from experience, but it serves its

purpose well.

>
> --
> Warm Regards,
>
> Lee

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.