I'd like to hear folks' thoughts about network "sniffing" strategies
for licensing/serial number enforcement. I will say that I'm not wild
about this approach in the first place, but a client has asked for it.
I have code that uses UDP sockets to multicast queries at critical
points in execution to see if other copies of the application with
the same serial number are running on the LAN, and if so whether the
total number exceeds the license limitations.
The problem with this strategy is that firewalls can easily be set up
to block UDP connections. It seems that if a UDP socket is blocked on
Windows, I get an error 107 when I try to multicast. On Mac OS X,
however, when the "Block UDP Traffic" option is selected in the
firewall's "Advanced" section, the socket gets no error, but just
acts as though the multicast went out, or perhaps it's the return
message that's blocked silently. In any case, I don't seem to be able
to detect the block on Mac OS X.
Thanks,
Peter
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