stun

This isn't true. In 2017 appear.in published some numbers. They saw ~15% were not able to do P2P. https://medium.com/@fippo/what-kind-of-turn-server-is-being-... Reading your stackoverflow link my guess is that you aren't using STUN. A P2P connection can't be established without a NAT hole punch. Also if possible I would avoid the terms `Full-cone NAT` and `Symmetric NAT` they don't do a good job of describing what is actually happening. NAT Mapping/NAT Filtering is the best way to describe it. I wrote a little bit about it here [0]. To see what type of NAT you have try stun-nat-behaviour[1] [0] https://webrtcforthecurious.com/docs/03-connecting/#nat-mapp... [1] https://github.com/pion/stun/tree/master/cmd/stun-nat-behavi...

NAT traversal is an impossible problem in practice in the general case (boo symmetric NATs), and the best-effort version is a solved problem since at least 2003 with the STUN protocol[1] which is part of WebRTC, and there are STUN implementations available in many languages[2]. [1]: https://datatracker.ietf.org/doc/html/rfc3489 [2]: For instance, Rust: https://github.com/webrtc-rs/stun & Go:https://github.com/pion/stun, and see this HN comment listing a few WebRTC implementations (which include STUN): https://news.ycombinator.com/item?id=26739253

It’s a little more nuanced than this. https://medium.com/the-making-of-whereby/what-kind-of-turn-s... fippo pulled the stats and saw 17% This also depends on your clients network. You can determine your NAT mapping type[0] and now ahead of time if you need a TURN server. To understand NAT behaviors more check out [1] [0] https://github.com/pion/stun/tree/master/cmd/stun-nat-behavi... [1] https://webrtcforthecurious.com/docs/03-connecting/#nat-mapp...

I think the most frustrating part is that people don't know what NAT they are behind. I wish WebRTC easily told people the attributes of their NAT. Not sure if it would help production deploys, but would make learning a lot easier. Someone contributed a really cool tool to Pion stun-nat-behavior[0] that I use a lot. It prints out NAT details. It uses the modern/correct details. I see a lot of docs that still use symmetric NAT etc.. RFC 4787 [1] suggests against all that. [0] https://github.com/pion/stun/tree/master/cmd/stun-nat-behavi... [1] https://tools.ietf.org/html/rfc4787#section-3