[Cryptography] peering through NAT

[Sidney Markowitz]

jamesd at echeque.com wrote on 9/05/19 11:45 PM:
> NAT makes it hard to contact a computer behind nat, but Bitcoin core has
> no problems with most nats, even when behind multiple levels of nats.
> 
> It does something to tell the nat to direct incoming messages on port
> 8333 to it, without the end user usually needing to manually set up port
> forwarding.

And I replied

> According to
> 
> https://bitcoin.org/en/full-node#port-forwarding
> 
>   and
> 
> https://bitcoin.stackexchange.com/questions/62022/what-is-the-benefit-of-opening-port-8333-to-a-client/62035#62035
> 
> that is not true.

Naturally as soon as I hit Send I remembered something contradictory.
Bitcoin core can use UPnP which is probably what you are thinking of

See https://dirkmittler.homeip.net/blog/archives/3340

and other results of a Google search for UPnP bitcoin core