Afaik you need some external resource to coordinate the punch. The STUN protocol is purpose built for this, and both clients need to be able to reach a STUN server to coordinate which port and public IP they’ll try to connect to each other on. I assume this does something similar but with p2p network tech instead of a STUN server.

Same as it ever was

Only if they both know who took Karl

I’m pretty high and I can’t make an ounce of sense of what you’re on about