running {x} licences on a network

Has anyone any experience on running only up to {x} (lets say 30) copies of a pieces of software on a network.

Would this simply involve creating a file on the first execution of a client... then incrementing the number stored in the file as a result of succesive copies being ran, with each successive copy in effect acknowldeging the fact the file existed and incrementing the count within the file ? thus eventually limiting the number of copies running at one time ?

Is this topic better handled by registry po - lava ?

thanks in advance for any light shedding - BP.

I would think the best way to do this is using a central license server (which I believe is what for example 3DStudioMSX uses) issuing tickets ala. X.509 or Kerberos?

Thanks FlameDuck, will root around with licence server methodology.

When coming up with a license system, make sure to account for client hardware and software problems as well.

e.g.:

1) Client program crashes. Upon restart, will it check out a second/third/fourth/whatever license, or keep using the same one?
2) People periodically upgrade their computers. Keep this in mind when assigning licenses to a client - can they un-register the program as well?
3) Furthermore -- Computers (and especially harddrives) can die. If you have a system where the client can register/unregister itself, keep in mind that there will be situations where a machine is no longer capable of unregistering itself with the server simply because it won't boot up.

Possible solution(s):
- Hand out a time-limited license, that expires after a certain time so dead machines won't perpetually take up a license
- Have an admin console on the server where you can force-revoke / reassign an existing license, freeing it up for another user. (Possibly sending a deactivation signal to the user currently using the license)
- Possibly build in a few grace licenses: e.g. If you have 10 licenses, allow 12 clients to use it but if there are more than the 10 licensed connection start throwing nag-screens upon application launch to notify the users about exceeding the server licenses. Meanwhile you can allow them to use the two grace licenses anyway.

(This is what the IBM AS/400 client express does)

thanks for the tips xlsior, I've some more research to do (;-)