Backend implementations

Bleak supports the following operating systems:

• Windows 10, version 16299 (Fall Creators Update) and greater

• Linux distributions with BlueZ >= 5.43 (See Linux backend for more details)

• OS X/macOS support via Core Bluetooth API, from at least version 10.11

• Partial Android support mostly using Python-for-Android/Kivy.

These pages document platform specific differences from the interface API.

Contents:

• Windows backend
  • Specific features for the Windows backend
  • API
• Linux backend
  • Special handling for write_gatt_char
  • Resolving services with get_services
  • Parallel Access
  • D-Bus Authentication
  • API
• macOS backend
  • Specific features for the macOS backend
  • API
• Android backend
  • Considerations on Android
  • API

Shared Backend API

Warning

The backend APIs are not considered part of the stable API and may change without notice.

Scanner

class bleak.backends.scanner.AdvertisementData(local_name: Optional[str], manufacturer_data: Dict[int, bytes], service_data: Dict[str, bytes], service_uuids: List[str], tx_power: Optional[int], rssi: int, platform_data: Tuple)

Wrapper around the advertisement data that each platform returns upon discovery

local_name: Optional[str]

The local name of the device or None if not included in advertising data.

manufacturer_data: Dict[int, bytes]

Dictionary of manufacturer data in bytes from the received advertisement data or empty dict if not present.

The keys are Bluetooth SIG assigned Company Identifiers and the values are bytes.

https://www.bluetooth.com/specifications/assigned-numbers/company-identifiers/

platform_data: Tuple

Tuple of platform specific data.

This is not a stable API. The actual values may change between releases.

rssi: int

The Radio Receive Signal Strength (RSSI) in dBm.

New in version 0.19.0.

service_data: Dict[str, bytes]

Dictionary of service data from the received advertisement data or empty dict if not present.

service_uuids: List[str]

List of service UUIDs from the received advertisement data or empty list if not present.

tx_power: Optional[int]

Tx Power data from the received advertising data or None if not present.

New in version 0.17.0.

bleak.backends.scanner.AdvertisementDataCallback

Type alias for callback called when advertisement data is received.

alias of Callable[[BLEDevice, AdvertisementData], Optional[Coroutine[Any, Any, None]]]

bleak.backends.scanner.AdvertisementDataFilter

Type alias for an advertisement data filter function.

Implementations should return True for matches, otherwise False.

alias of Callable[[BLEDevice, AdvertisementData], bool]

class bleak.backends.scanner.BaseBleakScanner(detection_callback: Optional[Callable[[BLEDevice, AdvertisementData], Optional[Coroutine[Any, Any, None]]]], service_uuids: Optional[List[str]])

Interface for Bleak Bluetooth LE Scanners

Parameters

• detection_callback – Optional function that will be called each time a device is discovered or advertising data has changed.

• service_uuids – Optional list of service UUIDs to filter on. Only advertisements containing this advertising data will be received.

call_detection_callbacks(device: BLEDevice, advertisement_data: AdvertisementData) → None

Calls all registered detection callbacks.

Backend implementations should call this method when an advertisement event is received from the OS.

create_or_update_device(address: str, name: str, details: Any, adv: AdvertisementData) → BLEDevice

Creates or updates a device in seen_devices.

Parameters

• address – The Bluetooth address of the device (UUID on macOS).

• name – The OS display name for the device.

• details – The platform-specific handle for the device.

• adv – The most recent advertisement data received.

Returns

The updated device.

register_detection_callback(callback: Optional[Callable[[BLEDevice, AdvertisementData], Optional[Coroutine[Any, Any, None]]]]) → Callable[[], None]

Register a callback that is called when an advertisement event from the OS is received.

The callback is a function or coroutine that takes two arguments: BLEDevice and AdvertisementData.

Parameters

callback – A function, coroutine or None.

Returns

A method that can be called to unregister the callback.

seen_devices: Dict[str, Tuple[BLEDevice, AdvertisementData]]

Map of device identifier to BLEDevice and most recent advertisement data.

This map must be cleared when scanning starts.

abstract set_scanning_filter(**kwargs) → None

Set scanning filter for the BleakScanner.

Parameters

**kwargs – The filter details. This will differ a lot between backend implementations.

abstract async start() → None

Start scanning for devices

abstract async stop() → None

Stop scanning for devices

bleak.backends.scanner.get_platform_scanner_backend_type() → Type[BaseBleakScanner]

Gets the platform-specific BaseBleakScanner type.

Client

Base class for backend clients.

Created on 2018-04-23 by hbldh <henrik.blidh@nedomkull.com>

class bleak.backends.client.BaseBleakClient(address_or_ble_device: Union[BLEDevice, str], **kwargs)

The Client Interface for Bleak Backend implementations to implement.

The documentation of this interface should thus be safe to use as a reference for your implementation.

Parameters

address_or_ble_device (BLEDevice or str) – The Bluetooth address of the BLE peripheral to connect to or the BLEDevice object representing it.

Keyword Arguments

• timeout (float) – Timeout for required discover call. Defaults to 10.0.

• disconnected_callback (callable) – Callback that will be scheduled in the event loop when the client is disconnected. The callable must take one argument, which will be this client object.

abstract async connect(**kwargs) → bool

Connect to the specified GATT server.

Returns

Boolean representing connection status.

abstract async disconnect() → bool

Disconnect from the specified GATT server.

Returns

Boolean representing connection status.

abstract async get_services(**kwargs) → BleakGATTServiceCollection

Get all services registered for this GATT server.

Returns

A bleak.backends.service.BleakGATTServiceCollection with this device’s services tree.

abstract property is_connected: bool

Check connection status between this client and the server.

Returns

Boolean representing connection status.

abstract property mtu_size: int

Gets the negotiated MTU.

abstract async pair(*args, **kwargs) → bool

Pair with the peripheral.

abstract async read_gatt_char(char_specifier: Union[BleakGATTCharacteristic, int, str, UUID], **kwargs) → bytearray

Perform read operation on the specified GATT characteristic.

Parameters

char_specifier (BleakGATTCharacteristic, int, str or UUID) – The characteristic to read from, specified by either integer handle, UUID or directly by the BleakGATTCharacteristic object representing it.

Returns

(bytearray) The read data.

abstract async read_gatt_descriptor(handle: int, **kwargs) → bytearray

Perform read operation on the specified GATT descriptor.

Parameters

handle (int) – The handle of the descriptor to read from.

Returns

(bytearray) The read data.

set_disconnected_callback(callback: Optional[Callable[[], None]], **kwargs) → None

Set the disconnect callback. The callback will only be called on unsolicited disconnect event.

Set the callback to None to remove any existing callback.

Parameters

callback – callback to be called on disconnection.

abstract async start_notify(characteristic: BleakGATTCharacteristic, callback: Callable[[bytearray], None], **kwargs) → None

Activate notifications/indications on a characteristic.

Implementers should call the OS function to enable notifications or indications on the characteristic.

To keep things the same cross-platform, notifications should be preferred over indications if possible when a characteristic supports both.

abstract async stop_notify(char_specifier: Union[BleakGATTCharacteristic, int, str, UUID]) → None

Deactivate notification/indication on a specified characteristic.

Parameters

char_specifier (BleakGATTCharacteristic, int, str or UUID) – The characteristic to deactivate notification/indication on, specified by either integer handle, UUID or directly by the BleakGATTCharacteristic object representing it.

abstract async unpair() → bool

Unpair with the peripheral.

abstract async write_gatt_char(characteristic: BleakGATTCharacteristic, data: typing_extensions.Buffer, response: bool) → None

Perform a write operation on the specified GATT characteristic.

Parameters

• characteristic – The characteristic to write to.

• data – The data to send.

• response – If write-with-response operation should be done.

abstract async write_gatt_descriptor(handle: int, data: typing_extensions.Buffer) → None

Perform a write operation on the specified GATT descriptor.

Parameters

• handle – The handle of the descriptor to read from.

• data – The data to send (any bytes-like object).

bleak.backends.client.get_platform_client_backend_type() → Type[BaseBleakClient]

Gets the platform-specific BaseBleakClient type.