alt Hacker NewsSTUN/TURN is basically icanhazip for WebRTC. STUN gives you your public IP:port. TURN is the same, but the returned IP:port is the one that had been dynamically allocated to you at time of querying, rather than the actual ones.
WebRTC clients take that STUN/TURN response and send to peers through out-of-band, through e.g. a lobby server chat mechanism, to set up the connection. This allows NAT table entries to be created as if they are outbound connection at both ends.
You can't make P2P connection with STUN/TURN alone. STUN/TURN is just a tool required for WebRTC.
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TURN is the last resort and isn't just signaling. It carries the traffic as well.
If you can make all the STUN servers fail from the perspective of the clients, you could hypothetically force them to use TURN servers that are more centralized and easier to spy on. STUN negotiates pipes n:n. TURN is closer to n:1.
> TURN is the same, but the returned IP:port is the one that had been dynamically allocated to you at time of querying, rather than the actual ones.
I don't know you mean by this, but I think you're confused. I have implemented STUN, so I know how it works. AFAIK, TURN doesn't reveal an address/port any different from that revealed by STUN, and cannot, because its discovery feature is STUN. (Also, a typical home user has only one internet-facing address, not a dynamic one plus another one.)
Rather, TURN provides a STUN address/port discovery service and a data relay service. The relay is for cases where two peers wishing to connect are both behind difficult NAT, meaning there is no quick and reliable way for them to directly connect even when they have their STUN results. So instead of connecting directly, they communicate through the relay.