Overview Go SFU — WebRTC media forwarding with Pion
The Gryt SFU (Selective Forwarding Unit) is a Go-based WebRTC media server built with Pion WebRTC. It receives audio tracks from each participant and forwards them to every other peer in the room without transcoding.
Selective forwarding : Routes audio streams with no transcodingPion WebRTC : ICE handling, STUN support, connection recoveryThread-safe : Concurrent handling of multiple connectionsLightweight : Minimal CPU and memory footprint
sfu/ ├── cmd/sfu/ # Entry point ├── internal/ │ ├── config/ # Environment-based configuration │ ├── websocket/ # Thread-safe WebSocket wrapper + handler │ ├── webrtc/ # Peer connection management │ ├── track/ # Media track lifecycle │ └── signaling/ # Offer/answer coordination └── pkg/types/ # Shared message structures cd packages/sfu cp env.example .env go run ./cmd/sfu Or with the start script:
Variable Default Description PORT5005HTTP server port STUN_SERVERSstun:stun.l.google.com:19302Comma-separated STUN servers ICE_UDP_PORT_MIN— Min UDP port for WebRTC media ICE_UDP_PORT_MAX— Max UDP port for WebRTC media ICE_ADVERTISE_IP— Public IP(s) to advertise in ICE candidates (comma-separated for multi-network) LOG_LEVELinfodebug, info, warn, errorMAX_CONNECTIONS1000Max concurrent connections
Event Payload Description joinJoinMessageJoin a room leaveLeaveMessageLeave room offerRTCSessionDescriptionWebRTC offer answerRTCSessionDescriptionWebRTC answer ice-candidateRTCIceCandidateICE candidate
Event Payload Description joinedJoinedMessageRoom join confirmation user-joinedUserJoinedMessagePeer joined user-leftUserLeftMessagePeer left offerRTCSessionDescriptionWebRTC offer answerRTCSessionDescriptionWebRTC answer ice-candidateRTCIceCandidateICE candidate
Client joins room — peer connection created
Client sends offer — SFU processes and creates answer
Client adds audio track — SFU forwards to other peers
Client leaves — tracks and connections cleaned up
Endpoint Description GET /healthHealth check GET /debug/roomsActive rooms GET /debug/peersPeer connections GET /debug/tracksMedia tracks GET /metricsPrometheus metrics
go mod download go test ./... go run -race ./cmd/sfu # with race detection