Do "write once run anywhere" engines require platform specific code for multiplayer?

Question

I've been investigating the myriad selection of mobile game dev engines that allow compilation of your code onto multiple target platforms, but, something I can't seem to figure out is if multi-platform "write it once" development is possible when you bring multiplayer into the equation.

I've looked at Unity and Monkey mostly, so far, but aside from seeing threads on the Monkey forum such as "I've developed such and such networking library for Monkey"... I can't find a definitive answer. That example is one of many that causes me concern.

Is it the case that if you used a cross platform engine, you'd have to write platform specific code for the networking portion of your game/app? (Even if the rest of the game did work on your target platforms with no/minimal platform-specific "jiggery".

I'm not talking about cross-platform multiplayer, but I do presume that'd be a happy by-product of a write-once-deploy-anywhere (within reason) networking solution.

Answer 1

Not being something that' I've personally tried with Unity (the whole networking part I mean), I can't give you a 100% sure answer, but I'm imagining that since whatever communication protocols Unity's using, they are (as standard networking protocols like TCP or UDP are) platform agnostic (i.e. if the platform supports TCP over IP, it will be able to connect to any other kind of platform that supports it).

Continuing on this, netoworking inside Unity should be platform agnostic as well. This question and answer on the Unity q&a site seems to support this:

http://answers.unity3d.com/questions/60247/cross-platform-network-transferring-variables.html