Just make sure you use a port high up in the range, dont use raw sockets, at least dont when you dont have the privs.
Use UDP , make sure its not constantly running, use intervals , say every 5 minutes.
Only make it active during certain hours or at "random" according to a algo known at both sides.
Do I need to say more
I have a totally sick idea for doing this but I want to code it myself first, when there is time.