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P2P Chat

Connection Strategy

The application uses a ICE framework for connection fallback

Direct Connection → Hole Punching → Relay Connection

Connection Flow:

  1. Open Ports with UPnP - Automatically configure router port forwarding when possible
  2. Direct Connection - Try direct TCP connection if both peers have public IPs or are on the same network
  3. Hole Punching - Use DCUtR (Direct Connection Upgrade through Relay) to punch through NATs
  4. Relay Connection - Route traffic through relay server using Circuit Relay v2

Peer Discovery

Peers discovery using Kademlia DHT (Distributed Hash Table)

  • Each peer advertises its presence using a rendezvous string (/private-chat/1.0.0)
  • Peers query the DHT to find others advertising the same rendezvous
  • Bootstrap nodes (IPFS public nodes) help new peers join the DHT network
  • Discovered peer addresses are cached locally for faster reconnection

Messaging Protocol

Protocol ID: /private-chat/1.0.0

Once a connection is established:

  • Chat messages are sent over libp2p streams
  • Messages are JSON-encoded for simplicity
  • Each message opens a new stream, sends data, then closes
  • The receiver's protocol handler decodes and displays messages

Addressing (Multiaddr)

libp2p uses multiaddr to encode multi-protocol network addresses:

  • Components: IP, transport (tcp/udp), protocol (quic/webtransport), certificate hashes, peer IDs.
  • Useful for rendezvous and signaling in decentralized apps.

TCP Connection:

/ip4/127.0.0.1/tcp/37967/p2p/12D3KooWABC123...

QUIC with WebTransport:

/ip4/127.0.0.1/udp/37260/quic-v1/webtransport/certhash/uEiABC.../p2p/12D3KooWXYZ...

Circuit Relay:

/p2p/12D3KooWRelay.../p2p-circuit/p2p/12D3KooWTarget...