bluetooth_core

The shared Rust crate behind the Bluetooth LE FFI. It wraps the btleplug host/central library and exposes a small synchronous, pollable C ABI that the bluetooth_dart package binds over dart:ffi, and that the bluetooth_cli binary uses directly.

BLE only. btleplug is host/central mode and does not support Bluetooth Classic.

What it does

A session owns a tokio runtime and the first available adapter. A background task drains btleplug's event stream into a bounded queue and caches discovered peripherals by id, so the host can poll events (device discovered/updated, connected/disconnected, notifications) without callbacks across the FFI boundary. Per-call operations (connect, discover services, read, write, subscribe, unsubscribe) bridge the async btleplug API back to the blocking ABI.

BLE payloads cross the ABI as JSON, because they are variable-length and nested (a peripheral carries maps of manufacturer/service data; a service carries a list of characteristics). The Dart side decodes these verbatim.

On macOS and iOS the crate also reads and requests the CoreBluetooth authorization status via objc2-core-bluetooth, which btleplug does not surface. Other platforms have no app-level Bluetooth permission and report unsupported.

Build and test

cargo build --manifest-path native/bluetooth_core/Cargo.toml
cargo test  --manifest-path native/bluetooth_core/Cargo.toml

The crate builds a cdylib (for FFI from Dart), a staticlib (for static linking, for example on iOS), and an rlib (so the in-repo CLI, example, and tests can call the API directly). A no-FFI example is included:

cargo run --manifest-path native/bluetooth_core/Cargo.toml --example scan

For Flutter apps the bluetooth_flutter plugin builds this crate automatically via cargokit; you do not build it by hand.