por parte del servidor

SmartFoxServer

bueno no lo he checado pero lo hare (lo juro)

http://www.smartfoxserver.com/

otro mas

http://photon.exitgames.com/

al parecer es muuuuuuy compatible con unity

bueno tambien esta neutron

Neutron® provides 24/7 game hosting and a rich-set of out-of-the-box features for the development
of multiplayer online games for PC, Mac, browser and mobile platforms including iPhone & Android.
Neutron allows game developers to easily create award winning multi-user gaming experiences while
it minimizes time-to-market and projects risks. Neutron integrates seamlessly with Photon to create
custom functionality if needed.

algo asi como un server pa ñoñear