Just going to say this right now; this seems absolutely ludicrous.
I've had a problem with playing Super Smash Bros. on Wii U ("Cannot connect to partner's device."; also happens for all Internet-based games [Splatoon, Monster Hunter 3, etc.]) Nintendo's support decided it'd be good for opening ports 1-65535. To make matters worse, my router's port forwarding does not let me port forward things for certain device. I can only open ports to ALL my devices. If anyone has a better option with the same effects, or could just generally give me a risk ratio, that'd be perfect.
P.S. The Wii U uses peer-to-peer connections. There's no servers for games. You have to trust seven different people that their Internet is good enough to connect to a locally-hosted group.