ADR-055: Integrated Sensing Server in Desktop App

Status

Accepted

Context

The RuView Desktop application (ADR-054) requires the WiFi sensing server to provide real-time CSI data, activity detection, and vital signs monitoring. Currently, the sensing server is a separate binary (wifi-densepose-sensing-server) that must be installed separately and found in the system PATH.

This creates several problems:

1. Distribution complexity: Users must install two binaries
2. Path issues: Binary may not be in PATH, causing "No such file or directory" errors
3. Version mismatch: Server and desktop app versions may diverge
4. Poor UX: Error messages about missing binaries confuse users

Decision

Bundle the sensing server binary inside the desktop application and provide intelligent binary discovery with clear fallback paths.

Binary Discovery Order

The desktop app searches for the sensing server in this order:

1. Custom path from user settings (server_path)
2. Bundled resources (Contents/Resources/bin/ on macOS)
3. Next to executable (same directory as the app binary)
4. System PATH (legacy fallback)

Implementation

fn find_server_binary(app: &AppHandle, custom_path: Option<&str>) -> Result<String, String> {
    // 1. Custom path from settings
    if let Some(path) = custom_path {
        if std::path::Path::new(path).exists() {
            return Ok(path.to_string());
        }
    }

    // 2. Bundled in resources
    if let Ok(resource_dir) = app.path().resource_dir() {
        let bundled = resource_dir.join("bin").join(DEFAULT_SERVER_BIN);
        if bundled.exists() {
            return Ok(bundled.to_string_lossy().to_string());
        }
    }

    // 3. Next to executable
    if let Ok(exe_path) = std::env::current_exe() {
        if let Some(exe_dir) = exe_path.parent() {
            let sibling = exe_dir.join(DEFAULT_SERVER_BIN);
            if sibling.exists() {
                return Ok(sibling.to_string_lossy().to_string());
            }
        }
    }

    // 4. System PATH
    // ... which lookup ...

    Err("Sensing server binary not found")
}

Bundle Configuration

In tauri.conf.json:

{
  "bundle": {
    "resources": [
      {
        "src": "../../target/release/wifi-densepose-sensing-server",
        "target": "bin/wifi-densepose-sensing-server"
      }
    ]
  }
}

Consequences

Positive

• Single package distribution: Users download one DMG/MSI/EXE
• Version alignment: Server and UI always match
• Better UX: No PATH configuration required
• Offline capable: Works without network access to download server

Negative

• Larger bundle size: ~10-15MB additional for server binary
• Build complexity: Must build server before bundling desktop
• Platform-specific: Need separate server binaries per platform

Neutral

• CI/CD workflow updated to build server before desktop
• GitHub Actions builds all platforms (macOS arm64/x64, Windows x64)

WebSocket Integration

The Sensing page connects to the bundled server's WebSocket endpoint:

• ws://127.0.0.1:{ws_port}/ws/sensing - Real-time CSI data stream
• ws://127.0.0.1:{ws_port}/ws/pose - Pose estimation stream

Message format:

interface WsSensingUpdate {
  type: string;
  timestamp: number;
  source: string;
  tick: number;
  nodes: WsNodeInfo[];
  classification: { motion_level: string; presence: boolean; confidence: number };
  vital_signs?: { breathing_rate_hz?: number; heart_rate_bpm?: number };
}

Security Considerations

• Server binary signed with same certificate as desktop app
• Communication over localhost only (127.0.0.1)
• No external network access by default
• Process spawned as child of desktop app (inherits permissions)

Related ADRs

• ADR-054: Desktop Full Implementation
• ADR-053: UI Design System
• ADR-052: Tauri Desktop Frontend