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Bluetooth Low Energy platform Agnostic Klient

Project description


Bleak Logo
Build and Test Documentation Status

Bleak is an acronym for Bluetooth Low Energy platform Agnostic Klient.

Bleak is a GATT client software, capable of connecting to BLE devices acting as GATT servers. It is designed to provide a asynchronous, cross-platform Python API to connect and communicate with e.g. sensors.


$ pip install bleak


  • Supports Windows 10, version 16299 (Fall Creators Update) or greater
  • Supports Linux distributions with BlueZ >= 5.43
  • OS X/macOS support via Core Bluetooth API, from at least OS X version 10.11

Bleak supports reading, writing and getting notifications from GATT servers, as well as a function for discovering BLE devices.


To discover Bluetooth devices that can be connected to:

import asyncio
from bleak import BleakScanner

async def run():
    devices = await
    for d in devices:

loop = asyncio.get_event_loop()

Connect to a Bluetooth device and read its model number:

import asyncio
from bleak import BleakClient

address = "24:71:89:cc:09:05"
MODEL_NBR_UUID = "00002a24-0000-1000-8000-00805f9b34fb"

async def run(address):
    async with BleakClient(address) as client:
        model_number = await client.read_gatt_char(MODEL_NBR_UUID)
        print("Model Number: {0}".format("".join(map(chr, model_number))))

loop = asyncio.get_event_loop()

See examples folder for more code, for instance example code for connecting to a TI SensorTag CC2650


All notable changes to this project will be documented in this file.

The format is based on Keep a Changelog, and this project adheres to Semantic Versioning.

0.12.1 (2021-07-07)


  • Changed minimum winrt package version to 1.0.21033.1. Fixes #589.


  • Fixed unawaited future when writing without response on CoreBluetooth backend. Fixes #586.

0.12.0 (2021-06-19)


  • Added mtu_size property for clients.
  • Added WinRT backend.
  • Added BleakScanner.discovered_devices property.
  • Added an event to await when stopping scanners in WinRT and pythonnet backends. Fixes #556.
  • Added BleakScanner.find_device_by_filter static method.
  • Added example.
  • Added optional command line argument to specify device to all applicable examples.


  • Added Programming Language :: Python :: 3.9 classifier in
  • Deprecated BleakScanner.get_discovered_devices() async method.
  • Added capability to handle async functions as detection callbacks in BleakScanner.
  • Added error description in addition to error name when BleakDBusError is converted to string.
  • Change typing of data parameter in write methods to Union[bytes, bytearray, memoryview].
  • Improved type hints in CoreBluetooth backend.
  • Use delegate callbacks for get_rssi() on CoreBluetooth backend.
  • Use @objc.python_method where possible in PeripheralDelegate class.
  • Using ObjC key-value observer to wait for BleakScanner.start() and stop() in CoreBluetooth backend.


  • Fixed KeyError when trying to connect to BLEDevice from advertising data callback on macOS. Fixes #448.
  • Handling of undetected devices in example. Fixes #487.
  • Added Optional typehint for BleakScanner.find_device_by_address.
  • Fixed linux_autodoc_mock_import in docs/
  • Minor fix for disconnection event handling in BlueZ backend. Fixes #491.
  • Corrections for the Philips Hue lamp example. Merged #505.
  • Fixed BleakClientBlueZDBus.pair() method always returning True. Fixes #503.
  • Fixed waiting for notification start/stop to complete in CoreBluetooth backend.
  • Fixed write without response on BlueZ < 5.51.
  • Fixed error propagation for CoreBluetooth events.
  • Fixed failed import on CI server when BlueZ is not installed.
  • Fixed notification value should be bytearray on CoreBluetooth. Fixes #560.
  • Fixed crash when cancelling connection when Python runtime shuts down on CoreBluetooth backend. Fixes #538.
  • Fixed connecting to multiple devices using a single BleakScanner on CoreBluetooth backend.
  • Fixed deadlock in CoreBluetooth backend when device disconnects while callbacks are pending. Fixes #535.
  • Fixed deadlock when using more than one service, characteristic or descriptor with the same UUID on CoreBluetooth backend.
  • Fixed exception raised when calling BleakScanner.stop() when already stopped in CoreBluetooth backend.

0.11.0 (2021-03-17)


  • Updated dotnet.client.BleakClientDotNet connect method docstring.
  • Added AdvertisementServiceData in BLEDevice in macOS devices
  • Protection levels (encryption) in Windows backend pairing. Solves #405.
  • Philips Hue lamp example script. Relates to #405.
  • Keyword arguments to get_services method on BleakClient.
  • Keyword argument use_cached on .NET backend, to enable uncached reading of services, characteristics and descriptors in Windows.
  • Documentation on troubleshooting OS level caches for services.
  • New example added: Async callbacks with a queue and external consumer
  • handle property on BleakGATTService objects
  • service_handle property on BleakGATTCharacteristic objects
  • Added more specific type hints for BleakGATTServiceCollection properties.
  • Added asyncio task to disconnect devices on event loop crash in BlueZ backend.
  • Added filtering on advertisement data callbacks on BlueZ backend so that callbacks only occur when advertising data changes like on macOS backend.
  • Added fallback to try org.bluez.Adapter1.ConnectDevice when trying to connect a device in BlueZ backend.
  • Added UART service example.


  • Fixed wrong OS write method called in write_gatt_descriptor() in Windows backend. Merged #403.
  • Fixed BaseBleakClient.services_resolved not reset on disconnect on BlueZ backend. Merged #401.
  • Fixed RSSI missing in discovered devices on macOS backend. Merged #400.
  • Fixed scan result shows ‘Unknown’ name of the BLEDevice. Fixes #371.
  • Fixed a broken check for the correct adapter in BleakClientBlueZDBus.
  • Fixed #445 and #362 for Windows.


  • Using handles to identify the services. Added handle abstract property to BleakGATTService and storing the services by handle instead of UUID.
  • Changed BleakScanner.set_scanning_filter() from async method to normal method.
  • Changed BlueZ backend to use dbus-next instead of txdbus.
  • Changed BleakClient.is_connected from async method to property.
  • Consolidated D-Bus signal debug messages in BlueZ backend.


  • Removed all __str__ methods from backend service, characteristic and descriptor implementations in favour of those in the abstract base classes.

0.10.0 (2020-12-11)


  • Added AdvertisementData class used with detection callbacks across all supported platforms. Merged #334.
  • Added BleakError raised during import on unsupported platforms.
  • Added rssi parameter to BLEDevice constructor.
  • Added detection_callback kwarg to BleakScanner constructor.


  • Updated minimum PyObjC version to 7.0.1.
  • Consolidated implementation of BleakScanner.register_detection_callback(). All platforms now take callback with BLEDevice and AdvertisementData arguments.
  • Consolidated BleakScanner.find_device_by_address() implementations.
  • Renamed “device” kwarg to “adapter” in BleakClient and BleakScanner. Fixes #381.


  • Fixed use of bare exceptions.
  • Fixed BleakClientBlueZDBus.start_notify() misses initial notifications with fast Bluetooth devices. Fixed #374.
  • Fix event callbacks on Windows not running in asyncio event loop thread.
  • Fixed on older versions of macOS. Fixes #331.
  • Fixed disconnect callback on BlueZ backend.
  • Fixed calling BleakClient.is_connected() on Mac before connection.
  • Fixed kwargs ignored in BleakScanner.find_device_by_address() in BlueZ backend. Fixes #360.


  • Removed duplicate definition of BLEDevice in BlueZ backend.
  • Removed unused imports.
  • Removed separate implementation of global discover method.

0.9.1 (2020-10-22)


  • Added new attribute _device_info on BleakClientBlueZDBus. Merges #347.
  • Added Pull Request Template.


  • Updated instructions on how to contribute, file issues and make PRs.
  • Updated AUTHORS.rst file with development team.


  • Fix well-known services not converted to UUIDs in BLEDevice.metadata in CoreBluetooth backend. Fixes #342.
  • Fix advertising data replaced instead of merged in scanner in CoreBluetooth backend. Merged #343.
  • Fix CBCentralManager not properly waited for during initialization in some cases.
  • Fix AttributeError in CoreBluetooth when using BLEDeviceCoreBluetooth object.

0.9.0 (2020-10-20)


  • Timeout for BlueZ backend connect call to avoid potential infinite hanging. Merged #306.
  • Added Interfaces API docs again.
  • Troubleshooting documentation.
  • noqa flags added to BleakBridge imports.
  • Adding a timeout on OSX so that the connect cannot hang forever. Merge #336.


  • BleakCharacteristic.description() on .NET now returns the same value as other platforms.
  • Changed all adding and removal of .NET event handler from +=/-= syntax to calling add_ and remove_ methods instead. This allows for proper removal of event handlers in .NET backend.
  • All code dependence on the BleakBridge is now removed. It is only imported to allow for access to UWP namespaces.
  • Removing internal method _start_notify in the .NET backend.
  • GattSession object now manages lifetime of .NET BleakClient connection.
  • BleakClient in .NET backend will reuse previous device information when reconnecting so that it doesn’t have to scan/discover again.


  • UUID property bug fixed in BlueZ backend. Merged #307.
  • Fix for broken RTD documentation.
  • Fix UUID string arguments should not be case sensitive.
  • Fix BleakGATTService.get_characteristic() method overridden with NotImplementedError in BlueZ backend.
  • Fix AttributeError when trying to connect using CoreBluetooth backend. Merged #323.
  • Fix disconnect callback called multiple times in .NET backend. Fixes #312.
  • Fix BleakClient.disconnect() method failing when called multiple times in .NET backend. Fixes #313.
  • Fix BleakClient.disconnect() method failing when called multiple times in Core Bluetooth backend. Merge #333.
  • Catch RemoteError in is_connected in BlueZ backend. Fixes #310,
  • Prevent overwriting address in constructor of BleakClient in BlueZ backend. Merge #311.
  • Fix nordic uart UUID. Merge #339.

0.8.0 (2020-09-22)


  • Implemented set_disconnected_callback in the .NET backend BleakClient implementation.
  • Added find_device_by_address method to the BleakScanner interface, for stopping scanning when a desired address is found.
  • Implemented find_device_by_address in the .NET backend BleakScanner implementation and switched its BleakClient implementation to use that method in connect.
  • Implemented find_device_by_address in the BlueZ backend BleakScanner implementation and switched its BleakClient implementation to use that method in connect.
  • Implemented find_device_by_address in the Core Bluetooth backend BleakScanner implementation and switched its BleakClient implementation to use that method in connect.
  • Added text representations of Protocol Errors that are visible in the .NET backend. Added these texts to errors raised.
  • Added pairing method in BleakClient interface.
  • Implemented pairing method in .NET backend.
  • Implemented pairing method in the BlueZ backend.
  • Added stumps and NotImplementedError on pairing in macOS backend.
  • Added the possibility to connect using BLEDevice instead of a string address. This allows for skipping the discovery call when connecting.


  • Support for Python 3.5.


  • BREAKING CHANGE All notifications now have the characteristic’s integer handle instead of its UUID as a string as the first argument sender sent to notification callbacks. This provides the uniqueness of sender in notifications as well.
  • Renamed BleakClient argument address to address_or_ble_device.
  • Version 0.5.0 of BleakUWPBridge, with some modified methods and implementing IDisposable.
  • Merged #224. All storing and passing of event loops in bleak is removed.
  • Removed Objective C delegate compliance checks. Merged #253.
  • Made context managers for .NET DataReader and DataWriter.


  • .NET backend loop handling bug entered by #224 fixed.
  • Removed default DEBUG level set to bleak logger. Fixes #251.
  • More coherency in logger uses over all backends. Fixes #258
  • Attempted fix of #255 and #133: cleanups, disposing of objects and creating new BleakBridge instances each disconnect.
  • Fixed some type hints and docstrings.
  • Modified the connected_peripheral_delegate handling in macOS backend to fix #213 and #116.
  • Merged #270, fixing a critical bug in get_services method in Core Bluetooth backend.
  • Improved handling of disconnections and is_connected in BlueZ backend to fix #259.
  • Fix for set_disconnected_callback on Core Bluetooth. Fixes #276.
  • Safer Core Bluetooth presence check. Merged #280.

0.7.1 (2020-07-02)


  • Improved, more explanatory error on BlueZ backend when BleakClient cannot find the desired device when trying to connect. (#238)
  • Better-than-nothing documentation about scanning filters added (#230).
  • Ran black on code which was forgotten in 0.7.0. Large diffs due to that.
  • Re-adding Python 3.8 CI “tests” on Windows again.


  • Fix when characteristic updates value faster than asyncio schedule (#240 & #241)
  • Incorrect corrected. (#244)

0.7.0 (2020-06-30)


  • Better feedback of communication errors to user in .NET backend and implementing error details proposed in #174.
  • Two devices example file to use for e.g. debugging.
  • Detection/discovery callbacks in Core Bluetooth backend Scanner implemented.
  • Characteristic handle printout in
  • Added scanning filters to .NET backend’s discover method.


  • Replace NSRunLoop with dispatch queue in Core Bluetooth backend. This causes callbacks to be dispatched on a background thread instead of on the main dispatch queue on the main thread. call_soon_threadsafe() is used to synchronize the events with the event loop where the central manager was created. Fixes #111.
  • The Central Manager is no longer global in the Core Bluetooth backend. A new one is created for each BleakClient and BleakScanner. Fixes #206 and #105.
  • Merged #167 and reworked characteristics handling in Bleak. Implemented in all backends; bleak now uses the characteristics’ handle to identify and keep track of them. Fixes #139 and #159 and allows connection for devices with multiple instances of the same characteristic UUIDs.
  • In requirements.txt and Pipfile, the requirement on pythonnet was bumped to version 2.5.1, which seems to solve issues described in #217 and #225.
  • Renamed HISTORY.rst to CHANGELOG.rst and adopted the Keep a Changelog format.
  • Python 3.5 support from macOS is officially removed since pyobjc>6 requires 3.6+
  • Pin pyobjc dependencies to use at least version 6.2. (PR #194)
  • Pin development requirement on bump2version to version 1.0.0
  • Added .pyup.yml for Pyup
  • Using CBManagerState constants from pyobj instead of integers.


  • Removed documentation note about not using new event loops in Linux. This was fixed by #143.
  • _central_manager_delegate_ready was removed in macOS backend.
  • Removed the bleak.backends.bluez.utils.get_gatt_service_path method. It is not used by bleak and possibly generates errors.


  • Improved handling of the txdbus connection to avoid hanging of disconnection clients in BlueZ backend. Fixes #216, #219 & #221.
  • #150 hints at the device path not being possible to create as is done in the get_device_object_path method. Now, we try to get it from BlueZ first. Otherwise, use the old fallback.
  • Minor documentation errors corrected.
  • CBManagerStatePoweredOn is now properly handled in Core Bluetooth.
  • Device enumeration in discover``and ``Scanner corrected. Fixes #211
  • Updated documentation about scanning filters.
  • Added workaround for isScanning attribute added in macOS 10.13. Fixes #234.

0.6.4 (2020-05-20)


  • Fix for bumpversion usage

0.6.3 (2020-05-20)


  • Building and releasing from Github Actions


  • Building and releasing on Azure Pipelines

0.6.2 (2020-05-15)


  • Added disconnection_callback functionality for Core Bluetooth (#184 & #186)
  • Added requirements.txt


  • Better cleanup of Bluez notifications (#154)
  • Fix for read_gatt_char in Core Bluetooth (#177)
  • Fix for is_disconnected in Core Bluetooth (#187 & #185)
  • Documentation fixes

0.6.1 (2020-03-09)


  • Including #156, lost notifications on macOS backend, which was accidentally missed on previous release.

0.6.0 (2020-03-09)

  • New Scanner object to allow for async device scanning.
  • Updated txdbus requirement to version 1.1.1 (Merged #122)
  • Implemented write_gatt_descriptor for Bluez backend.
  • Large change in Bluez backend handling of Twisted reactors. Fixes #143
  • Modified set_disconnect_callback to actually call the callback as a callback. Fixes #108.
  • Added another required parameter to disconnect callbacks.
  • Added Discovery filter option in BlueZ backend (Merged #124)
  • Merge #138: comments about Bluez version check.
  • Improved scanning data for macOS backend. Merge #126.
  • Merges #141, a critical fix for macOS.
  • Fix for #114, write with response on macOS.
  • Fix for #87, DIctionary changes size on .NET backend.
  • Fix for #127, uuid or str on macOS.
  • Handles str/uuid for characteristics better.
  • Merge #148, Run .NET backend notifications on event loop instead of main loop.
  • Merge #146, adapt characteristic write log to account for WriteWithoutResponse on macOS.
  • Fix for #145, Error in cleanup on Bluez backend.
  • Fix for #151, only subscribe to BlueZ messages on DBus. Merge #152.
  • Fix for #142, Merge #144, Improved scanning for macOS backend.
  • Fix for #155, Merge #156, lost notifications on macOS backend.
  • Improved type hints
  • Improved error handling for .NET backend.
  • Documentation fixes.

0.5.1 (2019-10-09)

  • Active Scanning on Windows, #99 potentially solving #95
  • Longer timeout in service discovery on BlueZ
  • Added timeout to constructors and connect methods
  • Fix for get_services on macOS. Relates to #101
  • Fixes for disconnect callback on BlueZ, #86 and #83
  • Fixed reading of device name in BlueZ. It is not readable as regular characteristic. #104
  • Removed logger feedback in BlueZ discovery method.
  • More verbose exceptions on macOS, #117 and #107

0.5.0 (2019-08-02)

  • macOS support added (thanks to @kevincar)
  • Merged #90 which fixed #89: Leaking callbacks in BlueZ
  • Merged #92 which fixed #91, Prevent leaking of DBus connections on discovery
  • Merged #96: Regex patterns
  • Merged #86 which fixed #83 and #82
  • Recovered old .NET discovery method to try for #95
  • Merged #80: macOS development

0.4.3 (2019-06-30)

  • Fix for #76
  • Fix for #69
  • Fix for #74
  • Fix for #68
  • Fix for #70
  • Merged #66

0.4.2 (2019-05-17)

  • Fix for missed part of PR #61.

0.4.1 (2019-05-17)

  • Merging of PR #61, improvements and fixes for multiple issues for BlueZ backend
  • Implementation of issue #57
  • Fixing issue #59
  • Documentation fixes.

0.4.0 (2019-04-10)

  • Transferred code from the BleakUWPBridge C# support project to pythonnet code
  • Fixed BlueZ >= 5.48 issues regarding Battery Service
  • Fix for issue #55

0.3.0 (2019-03-18)

  • Fix for issue #53: Windows and Python 3.7 error
  • Azure Pipelines used for CI

0.2.4 (2018-11-30)

  • Fix for issue #52: Timing issue getting characteristics
  • Additional fix for issue #51.
  • Bugfix for string method for BLEDevice.

0.2.3 (2018-11-28)

  • Fix for issue #51: dpkg-query not found on all Linux systems

0.2.2 (2018-11-08)

  • Made it compliant with Python 3.5 by removing f-strings

0.2.1 (2018-06-28)

  • Improved logging on .NET discover method
  • Some type annotation fixes in .NET code

0.2.0 (2018-04-26)

  • Project added to Github
  • First version on PyPI.
  • Working Linux (BlueZ DBus API) backend.
  • Working Windows (UWP Bluetooth API) backend.

0.1.0 (2017-10-23)

  • Bleak created.

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