Hi,

I want to support as many platforms as possible for networking, is there a good popular choice? What does Unity use?

Is there any particular features you want? If not then, the sockets API is available on pretty much every platform with networking and requires only minimal platform dependent code to work with (basically just WSAStartup() on Windows).

Unity's built in networking is basically a wrapper around Raknet. Raknet is a fine solution and can do many things for you quite well but it is for the most part just a messaging and RPC solution which you build on top of. Of course, without further information it is difficult to say what it is you are looking for, so just a basic overview of things you can look at:

Lowest language level items: These items provide just the raw communications abilities, everything else is up to you.

C/C++/Most languages - the low level berkeley sockets API is the underlying item for most OS's.

Net/Mono - the async event solution is your best bet for scaling decently.

Mid level C/C++ items: Wrappers around the underlying Berkeley sockets API, most importantly they use appropriate OS support to supply fairly scalable asynchronous access to the sockets in a clean manner compared to the very aged (well aged; often confusing but not really bad) underlying API. Again, transport of data is left to you.

Boost ASIO

Libev or LibEvent

Higher level items: Actual message passing protocols, identification utilities, rpc etc.

Raknet

Zeroc's ICE

kNet

plenty of others.

Without further information as to your level of interest and what you are trying to accomplish, this is the best way I can start you off. Go poke around at the various items and figure out what level you want to approach things first.

Thanks for the responses, the type of networking I want to add (or have the capability for) includes simple multiplayer games, cooperative game play, network classic dm style game play, database registration, online content streaming, scalable morpg server capability etc, chat server, voip server

I have got loads of ideas, however I can't easily implement all this myself so a good high level general purpose middleware solution (and hopefully free, gpl or mit) with hopefully some examples would be ideal ... I am not looking for the best of any, just need the platform coverage and stability ... this should more or less cover the network back end of any software project.

I might still use an engine for my current game, maybe unity or udk, however I prefer to see the code because I have experience.