Hehe. If you can't imagine that then you have a sheltered and probably very happy life. I don't care if it speaks ethernet, arcnet, twinax, X.25 or nothing at all, we'll find a way. By the time you can start sending UDP packets you are already on very solid footing.
Be happy if your dev environment does not include an emulated version of the real hardware that mysteriously does not seem to be 100% representative of the real thing.
Anything on mainframes or older systems that do not have ethernet.
Anything running Netware or equivalent (true, there you could probably hack some kind of interface but whether it would be reliable or not is another matter).
"somecounter:1|c"