WebRTC Transport Implementation & Updates

[Nkovaturient]

Discussion

• Comprehensive WebRTC transport implementation for py-libp2p, enabling browser-to-browser, browser-to-server, and server-to-server real-time peer-to-peer connections
• Issue: Add Support for WebRTC set-up in py-libp2p #546
• PR : Feat/add webrtc transport #780

✅ Core Transport Implementation

• Private-to-Private WebRTC: Circuit relay-based signaling for NAT traversal
• WebRTC-Direct: UDP hole punching for direct peer connections
• Stream Multiplexing: Multiple protocols over single WebRTC data channels
• Certificate Management: Self-signed certificates with proper hash encoding
• Protocol Registration: Full multiaddr support with WebRTC, WebRTC-Direct, and certhash protocols

Contributors

@Nkovaturient
@sukhman-sukh
@asmit27rai
@Winter-Soren

✅ Accomplished Tasks

WebRTC-Direct ( pvt-to-public)

• Stream read/write in webrtc-direct
• Fixed SDP, ICE msg transfer, ICE Candidate exchange
• Revamped Dialer and listener

Webrtc Pvt-to-Pvt

• listener & Protocol registration - Refactor WebRTC Private-to-Private Listener to Match js-libp2p Pattern Nkovaturient/py-libp2p#2

• Diagram

sequenceDiagram
    participant a as Browser A
    participant cr as CircuitRelayV2Peer
    participant b as Browser B
    participant stun as STUN Server
    b->>cr: Establish Relayed Connection (WebTransport, WebRTC)
    b-->>a: Shares its own relayed webrtc multiaddress (out of band)
    a->>b: Establishes a relayed connection to Browser 2
    a-->>a: Creates RTCPeerConnection with STUN server config, init DataChannel and SDP offer
    a->>b: Initiates libp2p /webrtc-signaling/0.0.1 protocol stream over relayed conection and sends SDP
    b-->>b: Creates RTCPeerConnection with STUN server config, sets Browser1's SDP offer, and creates SDP answer
    b->>a: Sends SDP answer over signaling stream
    a-->>a: Set SDP answer with RTCPeerConnection.setRemoteDescription
    a->>+stun: What's my public IP and port
    stun->>-a: Browser A observed ip and port: 8.8.8.1:63333
    b->>+stun: What's my public IP and port
    stun->>-b: Browser B observed ip and port: 6.6.6.1:52222
    b->a: exchange ICE candidates over signalling stream pass to RTCPeerConnection.addIceCandidate()
    b->a: Establish direct connection

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Fixes and TODOs:

• ICEUDPMUXListener- listening to STUN requests for webrtc-direct (under progress by @sukhman-sukh )
• Stream state management in webrtc as guided here
• Network-independent operation with smart timeout handling
• Real WebRTC transport connection testing with SDP generation and data channel setup
• Circuit-relay-v2 that supports relaying addr from server node to browser [
• Two Non-browser-nodes: TCP/QUIC hole punching with DCUtR to establish direct connection
• Demonstrate complete end-to-end connectivity via webRTC Private-to-Private & Private-to-Public Connections
• Demonstrate direct WebRTC connection with NAT traversal
• Demonstrate P2P connection through circuit relay

Transport Interop & Test Plans

• Discussion on Tests for WebRTC direct #839

1. Loopback test between two local py-peers
2. Browser-to-public peer via webrtc-direct with circuit relay
3. Robust-level: Testing with mixed network conditions (high latency, packet loss) to ensure resilience. Verifying reconnection logic when a peer temporarily drops. Adding logging hooks so we can trace the signaling handshake more easily if issues arise.

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[Nkovaturient]

@sukhman-sukh , @asmit27rai, @Winter-Soren : kindly comment down your progress, updates, or blockers/issues(if any) to ensure coordination and collaborated timely guidance on each.
Thank you for your continuous efforts.

ccing: @seetadev , @acul71 , @AkMo3 for insighful guidance and rectifications on the same.