scratch-link-rs

Multiplatform Scratch Link replacement in Rust. Speaks the Scratch Link JSON-RPC protocol over WebSocket on ws://127.0.0.1:20111/scratch/ble and bridges it to BLE via btleplug (Windows/WinRT, macOS+ iOS/CoreBluetooth, Linux/BlueZ, Android).

Features

• Multiple simultaneous BLE devices: each WebSocket connection is an isolated session (discovery session or one connected peripheral), like the original.
• Discovery with Web-BLE-style filters (services, name, namePrefix), announces didDiscoverPeripheral including already-cached devices.
• GATT: read, write (with/without response), startNotifications, stopNotifications, getServices, getCharacteristics.
• characteristicDidChange notifications (base64 payloads).
• DeviceDisconnected closes the session socket, matching the JS reference.
• Plain GET http://127.0.0.1:20111 answers 200 OK (health check).
• Scanning is refcounted across sessions and paused while a connect is in flight (BlueZ cannot connect reliably during active LE discovery).

Build & Run

cargo build --release
./target/release/scratch-link-rs

Logging via RUST_LOG, default scratch_link_rs=info.

Protocol surface

Method	Notes
getVersion	{protocol: "1.3"}
ping	42
discover	starts/refreshes scanning, replies null, then didDiscoverPeripheral notifications
connect	{peripheralId}, 15 s timeout + service discovery, replies null
disconnect	drops the session's peripheral
read	{serviceId, characteristicId, startNotifications?} → base64 result (+ encoding sibling, like the reference impl)
write	{serviceId, characteristicId, message, encoding?, withResponse?} → bytes written
startNotifications / stopNotifications	{serviceId, characteristicId}
getServices / getCharacteristics	UUID lists

UUID params accept 128-bit strings or 16/32-bit shorthand (expanded to the Bluetooth base UUID).

License

Dual-licensed under MIT or Apache-2.0, at your option.