I don't know what the take away is supposed to be here. Everything spoken about here is already basic network programming. It seems to focus on higher level plumbing and geeks out on state management even though this is just a matter of preference and has nothing to do with networking.

The most interesting thing I learned from the article is that cloudflare runs a public stun server. But even that isn't helpful because the 'good' and 'useful' version of the STUN protocol is the first version of the protocol which supports 'change requests' -- a feature that allows for NAT enumeration. Later versions of the STUN protocol removed that feature thanks to the 'helpful suggestions' of Cisco engineers who contributed to the spec.