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Transport Layer

Unified transport abstraction for Radix Relay.

Overview

The transport layer provides a unified interface for multiple communication mechanisms:

  • Nostr - ✅ Fully Implemented - Internet-based relay network
  • BLE - 📋 Planned - Local mesh networking
  • Future protocols - Extensible design

Nostr Transport (Implemented)

Components

WebSocket Transport (lib/transport/)

  • Boost.Beast-based async WebSocket implementation
  • TLS/SSL support (wss:// required for security)
  • Connection lifecycle management
  • Read/write operations with coroutines

Nostr Protocol (lib/nostr/)

  • Event types: OK, EOSE, EVENT, REQ, CLOSE
  • Message kinds: encrypted_message (40001), bundle_announcement (30078)
  • JSON serialization/deserialization
  • Tag parsing and validation

Session Orchestrator

  • Coordinates transport, Signal bridge, and presentation layers
  • Handles bundle discovery and session establishment
  • Message routing and decryption
  • Automatic key maintenance and bundle republishing

Features

✅ Connection Management

  • Async connect to Nostr relays
  • TLS/SSL encryption (wss://)
  • Connection state tracking
  • Error handling and recovery

✅ Message Handling

  • Event-based architecture
  • Subscription management
  • Request tracking with timeouts
  • Duplicate message detection

✅ Integration

  • Works with Signal Protocol for E2E encryption
  • Contact management and aliases
  • Bundle announcement publishing
  • Session persistence

Implementation

The Nostr transport implementation includes:

  • Connecting to real Nostr relays (e.g., relay.damus.io)
  • Publishing pre-key bundles
  • Discovering peer bundles
  • Establishing encrypted sessions
  • Sending/receiving encrypted messages

BLE Transport (Planned)

Planned Components

  • BLE device discovery
  • GATT server/client implementation
  • Mesh networking protocol
  • Platform-specific APIs (BlueZ, CoreBluetooth, etc.)

Design Goals

  1. Abstraction - Uniform interface regardless of transport
  2. Flexibility - Easy to add new transports
  3. Efficiency - Minimal overhead
  4. Reliability - Handle connection failures gracefully