I've actually done this a few times in my life, it's not any more difficult than having an API for two pieces of software to communicate across. Usually on the hardware side, they'll implement a regular ethernet stack so they follow all the same rules and guidelines that you do on the PC software side. As a matter of fact, most people usually buy an Ethernet "core" that gives them the functionality without implementing it themselves, same as you using the Winsock library. The only trick is really understanding the bytes received and what they mean (just an exercise in arranging structures and casting bytes).

No probs - I only thought about it as I had the same problem last week :-)

I forgot to mention something: If your class in your class hierarchy is abstract or you simply know that you never create an instance of that class then you can use the __declspec(novtable) on the class in VC++. This way the ctor won't contain the automatically generated vtable initializer. If you don't call any virtual methods from the ctor (and you shouldn't) then its enough to have vtable initialization only in the actual class ctor from which you create the instance (in the "most derived" one). In practice I used this optimization only once because usually this thing is not the bottleneck.