The STUN protocol in gortc

STUN is acronym for Session Traversal Utilities for NAT and is used by ICE to provide peer-to-peer connectivity for users behind NAT it WebRTC. See RFC 5389 for protocol specification and ernado/stun for implementation.

Also, the TURN protocol which relays traffic for agents (users) that are failed to reach p2p connectivity is extension of STUN.