ad hoc using WiFi only

[LunaMoo]

All devices must see each other in some kind of network and be able to freely connect with device you run server on. And that's pretty much all for requirements.

What kind of network you create and what kind of devices you connect to it, depends purely on you and your ability of doing so, and in all cases a wifi router which I belive you ask about is pretty much easiest solution.
When you play on lan you don't have to deal with any of those adware third party programs that people playing online recommend using, pretty much as long as the game works with current(unfortunately unfinished yet) ppsspp adhoc implementation it will work on lan much easier and better than going through the net.