The first article in this series was the traps inside the code. The second was the layer underneath — the candidates that lie, the UDP firewall nobody looks at, the reverse proxy that reaps an idle socket. This one is about the piece people reach for when those two are not enough: the relay. TURN is the part of WebRTC that gets configured last, in a hurry, by copying a config off a blog post. That is exactly how you end up with a relay that passes every "is it running?" check and still produc...