What's the best solution for a 4-player co-op game, and where's the tutorial?

Hi, I've been banging my head against the monolith of multiplayer for a while, so I figured I'd inquire here. A question in 2 parts.

1) What would be the best solution for a simple ~4 player co-op game? Co-op means there's no need for cheat protection or other such validations, as there's no point in getting advantage over other players. You invited everyone present. You only need one person to host who can then pass out his IP to his friends. I don't need server browsers, dedicated servers, or any such complications and couldn't afford the overhead in the first place.

2) Where's a good, free tutorial for this solution?

(TLDNR can stop here, the following is only for clarification)

To get more complicated, I'm looking to make a simple, co-op, D&D style dungeon crawler. Players would either host, or enter a host's IP, then be asked to choose their class. They would need to communicate their locations, current statistics equipment to one another as well as those of the enemies present and the state of the world itself. Certain things like enemy spawns, item drops, and such will need to be kept consistent across the experience, but minor differences in, say, the exact path of a projectile would be irreverent.

 

1) The unity networking is built for this stuff.
2) There is none.

 

http://forum.unity3d.com/threads/216804-Tutorial-Building-a-Multiplayer-FPS-in-Unity-3d

This is uses Photon and while it's making a UT clone, because it relies on the client to process everything, it'll suit your Co-op scenario just fine.

 

4 PLAYER FOR NINTENDO SWITCH

 

Literally anything will work for this. It depends on your budget, do you need match making, what platform? ect...

 

Conecting using the ip can be dangerous, and the host would need to port forward, which people doesnt like. I would use a relay like steamworks. If you don want to use it directly, you can use a steam transport for netcode, which, as fholm said, was made for this.