WebRTC-Direct examples in every language: no signaling, plus TURN and STUN modes

The latest grpc-over-datachannels release ships WebRTC-Direct examples for every supported language — generated, like the runtimes themselves. A server listens on a UDP socket and prints a certhash multiaddr (/ip4/…/udp/…/webrtc-direct/certhash/f…); a client dials that address and gets a DTLS/SCTP data channel carrying plain gRPC frames. No signaling server, no SDP exchange.

Three ways to connect

Direct — the client dials the multiaddr straight over UDP. This is the LAN and public-host path, and the server prints everything a client needs on one MULTIADDR line.

Via TURN — a client behind a symmetric NAT allocates a relay on a TURN server and dials the same listener through it. TURN is purely a client-side tool here: the server never changes and never learns TURN exists. Set DIRECT_TURN=host:3478 (plus user/password) or pass --turn to the sidecar.

Full ICE with STUN — a Direct listener gathers no ICE candidates, so STUN belongs to the peer mode: the Go and Rust examples include peer-serve/peer-dial modes where GRPC_DC_STUN=stun.l.google.com:19302 enables server-reflexive candidate gathering, with SDP exchanged through files as a stand-in for any signaling channel. Browsers join through this same full-ICE path — a browser has no UDP sockets, so it can never dial a multiaddr directly.

Every language, one shape

JavaScript, Go, and Rust embed the WebRTC stack and run the examples natively. The other thirteen languages — Python, Ruby, PHP, Lua, C, C++, Dart, Java, Kotlin, Scala, Swift, C#, and Zig — reach WebRTC-Direct through their generated SidecarTransport plus the small Rust direct_sidecar bridge, so the language code is identical whether the path is direct or TURN. Each example has serve and dial modes, and the compose file in examples/direct wires servers and clients together with a shared /signal volume as the whole client→server handoff, coturn fixture included.

Try it

Everything lands in examples/direct in the upcoming v0.36.0 release (December 1): start the Node server, copy its multiaddr, and dial it from any language. The per-language catalog lives at browser-grpc/examples. Two honest limits, documented in the README: a NATted listener still needs a port forward, a public host, or the TURN dial — STUN alone cannot make an inbound UDP listener reachable — and browser + tunnel + TURN is not supported, because the quick tunnels are TCP-only.