Interoperability between platforms

So, lets say i want to do a Turn based strategy game (See Advance wars on Nintendo DS for a reference) ... I know this can be done with Unity... Now, lets say i made this game in PC, then adjusted a few things and ported to Mac, then tweaked with a new UI and new controls, and ported it to iOS and Android devices... Would it be possible to make them possible to play between them?? Like a Cross-Platform Multiplayer game (See Portal 2 for example between PC and PS3)