[mightyham]

In practice, P2P over ipv6 is totally screwed because there are no widely supported protocols for dynamic firewall pinholing (allowing inbound traffic) on home routers, whereas dynamic ipv4 NAT configuration via UPnP is very popular and used by many applications.

[johncolanduoni]

Most home routers do a form of stateful IPv6 firewall (and IPv4 NAT for that matter) compatible with STUN. UPnP is almost never necessary and has frequent security flaws in common implementations.

[immibis]

You just send a (UDP) packet to the other side's address and port and they send one to yours. The firewalls treat it as an outbound connection on both sides.

[mightyham]

I don't believe that's true. You would still need something like UDP hole punching to bootstrap the inbound flow on both sides first. Also you would still only be limited to UDP traffic, TCP would still be blocked.

[immibis]

Sending one packet outbound is hole punching. It's really that simple. Since there's no NAT, you don't need to bother with all the complexity of trying to predict the port number on the public side of the NAT. You just have two sides send at least one packet to each other, and that opens the firewalls on both sides.

[GoblinSlayer]

You just need to tell the other side that you want to connect.

[beeflet]

just don't use a firewall