✨ Networking - Implement P2P Handshake & Messaging

[jordyfontoura]

✨ Networking — Implement P2P Handshake & Messaging

Description

We need to implement the initial P2P networking layer for Multibonk.
This includes the ability for two game clients to:

• Discover and establish a direct peer-to-peer connection (with NAT traversal if possible).
• Exchange simple messages reliably (e.g., ping/pong).
• Fallback to relay (TURN) if direct connection fails.

This is the foundation for the multiplayer system, later features such as state synchronization and input replication will depend on this.

Scope

• Create a NetworkManager (or equivalent) module to handle P2P connections.
• Support WebRTC DataChannels for initial implementation (abstracted for future replacement if needed).
• Implement a handshake protocol:
  • Exchange peer IDs.
  • Confirm readiness before sending game data.
• Basic messaging API:
  • sendMessage(type, payload) for outgoing messages.
  • onMessage(type, callback) for incoming messages.
• Add minimal logging for debugging connections.

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Acceptance Criteria

• Two local game instances can connect directly (when network permits).
• Connection attempt retries at least 3 times before failing.
• If direct connection fails, a fallback relay (TURN) server can be used (configurable).
• Successful handshake confirms both peers are ready (log confirmation).
• Ability to send a simple ping message and receive a pong response.
• Network errors are logged with clear messages (no silent failures).
• Unit tests for handshake and message serialization/deserialization.

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Definition of Done

• Code merged into main behind a feature flag (if applicable).
• README or docs/networking.md updated with connection flow and developer setup.
• CI passes with new networking tests.

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Additional Notes

• Future tasks will build on this to add state replication and client prediction.
• The relay server config can initially be a simple TURN server URL/env variable.