#bluetooth #bluez #ble #gatt #l2cap

bluer

BlueR: official Rust interface to the Linux Bluetooth protocol stack (BlueZ)

4 releases

0.10.3 Jul 18, 2021
0.10.2 Jul 6, 2021
0.10.1 Jul 6, 2021
0.10.0 Jul 6, 2021

#45 in Hardware support

43 downloads per month
Used in bluer-tools

BSD-2-Clause

280KB
5K SLoC

BlueR - Official BlueZ Bindings for Rust

crates.io page docs.rs page BSD-2-Clause license

This library provides the official Rust interface to the Linux Bluetooth protocol stack (BlueZ). Both publishing local and consuming remote GATT services using idiomatic Rust code is supported. L2CAP sockets are presented using an API similar to Tokio networking.

The following functionality is provided:

  • Bluetooth adapters
    • enumeration
    • configuration of power, discoverability, name, etc.
    • hot-plug support through change events stream
  • Bluetooth devices
    • discovery
    • querying of address, name, class, signal strength (RSSI), etc.
    • Bluetooth Low Energy advertisements
    • change events stream
    • connecting and pairing
  • consumption of remote GATT services
    • GATT service discovery
    • read, write and notify operations on characteristics
    • read and write operations on characteristic descriptors
    • optional use of low-overhead AsyncRead and AsyncWrite streams for notify and write operations
  • publishing local GATT services
    • read, write and notify operations on characteristics
    • read and write operations on characteristic descriptors
    • two programming models supported
      • callback-based interface
      • low-overhead AsyncRead and AsyncWrite streams
  • sending Bluetooth Low Energy advertisements
  • Bluetooth authorization agent
  • efficient event dispatching
    • not affected by D-Bus match rule count
    • O(1) in number of subscriptions
  • L2CAP sockets
    • stream oriented
    • sequential packet oriented
    • datagram oriented
    • async IO interface with AsyncRead and AsyncWrite support
  • database of assigned numbers
    • manufacturer ids
    • GATT services, characteristics and descriptors

Currently, classic Bluetooth functionality is mostly unimplemented except for device discovery. However, pull requests and contributions are welcome!

History

This project started as a fork of blurz but has since then become a full rewrite. It was published under the name blez before it was designated the official Rust interface to BlueZ and renamed to BlueR. Documentation has been mostly copied from the BlueZ API specification, but also adapted where it makes sense.

Crate features

All crate features are enabled by default.

  • bluetoothd: Enables all functions requiring a running Bluetooth daemon. For building, D-Bus library headers, provided by libdbus-1-dev on Debian, must be installed.
  • id: Enables database of assigned numbers.
  • l2cap: Enables L2CAP sockets.

Requirements

This library has been tested with BlueZ version 5.59 with additional patches from the master branch applied. Older versions might work, but be aware that many bugs related to GATT handling exist. Refer to the official changelog for details.

If any bluetoothd feature is used the Bluetooth daemon must be running and configured for access over D-Bus. On most distributions this should work out of the box.

Configuration

The following options in /etc/bluetooth/main.conf are helpful when working with GATT services.

[GATT]
Cache = no
Channels = 1

This disables the GATT cache to avoid stale data during device discovery.

By only allowing one channel the extended attribute protocol (EATT) is disabled. If EATT is enabled, all GATT commands and notifications are sent over multiple L2CAP channels and can be reordered arbitrarily by lower layers of the protocol stack. This makes sequential data transmission over GATT characteristics more difficult.

Building

When cloning this repository make sure to use the following command. Otherwise the build will fail with file not found errors.

git clone --recursive https://github.com/bluez/bluer.git

D-Bus development headers are required for building.

Troubleshooting

The library returns detailed errors received from BlueZ.

Set the Rust log level to trace to see all D-Bus communications with BlueZ.

In some cases checking the Bluetooth system log might provide further insights. On Debian-based systems it can be displayed by executing journalctl -u bluetooth. Check the bluetoothd man page for increasing the log level.

Sometimes deleting the system Bluetooth cache at /var/lib/bluetooth and restarting bluetoothd fixes persistent issues with device connectivity.

Examples

Refer to the API documentation and examples folder for examples.

The following example applications are provided.

  • discover_devices: Discover Bluetooth devices and print their properties.

  • gatt_client: Simple GATT client that calls read, write and notify on a characteristic.

  • gatt_server_cb: Corresponding GATT server implemented using callback programming model.

  • gatt_server_io: Corresponding GATT server implemented using IO programming model.

  • gatt_echo_client: Simple GATT client that connects to a server and sends and receives test data.

  • gatt_echo_server: Corresponding GATT server that echos received data.

  • l2cap_client: Simple L2CAP socket client that connects to a socket and sends and receives test data.

  • l2cap_server: Corresponding L2CAP socket server that echos received data.

  • le_advertise: Register Bluetooth LE advertisement.

  • list_adapters: List installed Bluetooth adapters and their properties.

Use cargo run --example <name> to run a particular example application.

Tools

See the BlueR tools crate for tools that build on this library.

Dependencies

~4–5.5MB
~98K SLoC