Can't connect to 2 BLE clients in parallel in Buster RPI4

• bleak version: 0.8.0
• Python version: 3.8.5
• Operating System: Debian 10 (Buster)
• BlueZ version (bluetoothctl -v) in case of Linux: 5.54

Description

related to #345 #215
I tried to connect to two clients (Nordic boards) the context is connecting over BLE from RPI4 to NORDIC over NORDIC dongle.

What I Did

connect to two clients in parallels for data notifications from clients.

from bleak import BleakClient
import asyncio

notify_uuid = "04831524-6c9d-6ca9-5d41-03ad4fff4abb"


def callback(sender, data):
    print(sender, data)


def run(addresses):
    loop = asyncio.get_event_loop()

    tasks = asyncio.gather(
        *(connect_to_device(address, loop) for address in addresses)
    )

    loop.run_until_complete(tasks)


async def connect_to_device(address, loop):
    print("starting", address, "loop")
    async with BleakClient(address, loop=loop, timeout=10.0) as client:

        print("connect to", address)
        try:
            await client.start_notify(notify_uuid, callback)
            await asyncio.sleep(10.0)
            await client.stop_notify(notify_uuid)
        except Exception as e:
            print(address + " : " + str(e))

    print("disconnect from", address)

if __name__ == "__main__":
    run(['D0:6D:E5:40:07:D3', 'FE:5D:07:FE:7A:93' ])

Output

try connecting to both clients in parallel - managed to connect only to 1 client at a time, never connected to both in parallel:

test 1: starting D0:6D:E5:40:07:D3 loop starting FE:5D:07:FE:7A:93 loop connect to FE:5D:07:FE:7A:93 21 bytearray(b’\x01\x00\x00\x00\x02\x81\xbfL\x15’) 21 bytearray(b’\x02\x00\x00\x00\x08O,9\xb2’) 21 bytearray(b’\x03\x00\x00\x00\x08\xff\x05Y\x8f’) 21 bytearray(b’\x04\x00\x00\x00\x0fLL\x1d\xa3’) 21 bytearray(b’\x05\x00\x00\x00\ns\x91\x17\xee’) 21 bytearray(b’\x06\x00\x00\x00\x02\x91cl\xa7’) 21 bytearray(b’\x07\x00\x00\x00\x08?\xa3\xd9z’) 21 bytearray(b’\x08\x00\x00\x00V\x1dHZt’) 21 bytearray(b’\t\x00\x00\x00\x10\x08\x85\x85\xd6’) 21 bytearray(b’\n\x00\x00\x00\xc1\xff\xff\xff\xff\xff\xff\xff\xff\x01\xe6\x15\xdd\xc3’) 21 bytearray(b’\x0b\x00\x00\x00\x02 \xa7\xfc_‘) 21 bytearray(b’\x0c\x00\x00\x00\x08.\x92\t\r’) 21 bytearray(b’\r\x00\x00\x00\x08\x9e\xbbi0’) 21 bytearray(b’\x0e\x00\x00\x00\x0f\xedT\xad\xe9’) 21 bytearray(b’\x0f\x00\x00\x00\n\xd2\x89\xa7\xa4’) 21 bytearray(b’\x10\x00\x00\x00\x02\xb3\x01\xccH’) 21 bytearray(b’\x11\x00\x00\x00\x08\x1d\xc1y\x95’) 21 bytearray(b’\x12\x00\x00\x00V>\xc7\n^‘) 21 bytearray(b’\x13\x00\x00\x00\x10+\n\xd5\xfc’) 21 bytearray(b’\x14\x00\x00\x00\xc2\xff\xff\xff\xff\xff\xff\xff\xff\x01\t\xc7\xc3\x85’) disconnect from FE:5D:07:FE:7A:93 connect to D0:6D:E5:40:07:D3 21 bytearray(b’\x01\x00\x00\x00\x02\x81\xbfL\x15’) 21 bytearray(b’\x02\x00\x00\x00\x08O,9\xb2’) 21 bytearray(b’\x03\x00\x00\x00\x07n\x18\xe6\x1f’) 21 bytearray(b’\x04\x00\x00\x00/\x84ls\x98’) 21 bytearray(b’\x05\x00\x00\x00\ns\x91\x17\xee’) 21 bytearray(b’\x06\x00\x00\x00\x10\xd9\x12\xd5T’) 21 bytearray(b’\x07\x00\x00\x00LVR1234567890123_\xed\v’) 21 bytearray(b’\x08\x00\x00\x00\x12\x94\xcd\xeb\x05’) 21 bytearray(b’\t\x00\x00\x00\x0b\xe4L\xe0\‘) 21 bytearray(b’\n\x00\x00\x002.0.0.20000e>x0’) 21 bytearray(b’\x0b\x00\x00\x00\x1av?\x90L’) 21 bytearray(b’\x0c\x00\x00\x00\x020{\xdc\xed’) 21 bytearray(b’\r\x00\x00\x00\x10\xc8#\x05#‘) 21 bytearray(b’\x0e\x00\x00\x00\x03\xc6\x18\x1b\xe0’) 21 bytearray(b’\x0f\x00\x00\x00\x1a\xb6\x99\x10\xb9’) 21 bytearray(b’\x10\x00\x00\x00\x02\xb3\x01\xccH’) 21 bytearray(b’\x11\x00\x00\x00\x10KY\x15\x86’) 21 bytearray(b’\x12\x00\x00\x00\x04\xe6\xf7o\xdb’) 21 bytearray(b’\x13\x00\x00\x00\x1a5\xe3\x00\x1c’) 21 bytearray(b’\x14\x00\x00\x00\x02s\xa7L\xbd’) 21 bytearray(b’\x15\x00\x00\x00\x10\x8b\xff\x95s’) 21 bytearray(b’\x16\x00\x00\x00\x05\xb0a\xe8Y’) 21 bytearray(b’\x17\x00\x00\x00\x1a\xf5E\x80\xe9’) 21 bytearray(b’\x18\x00\x00\x00\x02rJ\xbcx’) 21 bytearray(b’\x19\x00\x00\x00\x10\x8a\x12e\xb6’) 21 bytearray(b’\x1a\x00\x00\x00\x06\x0b\xdd\x11\x05’) 21 bytearray(b’\x1b\x00\x00\x00\x02\xa20\x1c?‘) 21 bytearray(b’\x1c\x00\x00\x00\x08\xac\x05\xe9m’) 21 bytearray(b’\x1d\x00\x00\x00\x08\x1c,\x89P’) 21 bytearray(b’\x1e\x00\x00\x00\x0fo\xc3M\x89’) 21 bytearray(b’\x1f\x00\x00\x00\nP\x1eG\xc4’) 21 bytearray(b’ \x00\x00\x00\x025\xb9\xed\xe9’) 21 bytearray(b’!\x00\x00\x00\x08\x9byX4’) 21 bytearray(b’“\x00\x00\x00Y)b\x94o’) 21 bytearray(b’#\x00\x00\x00\x10\xad\xb2\xf4]‘) 21 bytearray(b’$\x00\x00\x00\xc2\xff\xff\xff\xff\xff\xff\xff\xff\x01\xbd\x83\x15.‘) 21 bytearray(b’%\x00\x00\x00\x02E6\r!‘) 21 bytearray(b’&\x00\x00\x00\x08\x8b\xa5x\x86’) 21 bytearray(b”'\x00\x00\x00\x08;\x8c\x18\xbb") 21 bytearray(b’(\x00\x00\x00\x0fI\x8e,\xa7’) 21 bytearray(b’)\x00\x00\x00\nvS&\xea’) 21 bytearray(b’*\x00\x00\x00\x02\x94\xa1]\xa3’) 21 bytearray(b’+\x00\x00\x00\x08:a\xe8~‘) 21 bytearray(b’,\x00\x00\x00YH\xdc\xa4\xd0’) disconnect from D0:6D:E5:40:07:D3

[cshablin]

Looking through existing issues, I came across this which is likely to be a challenge as I’m working with a system with two, BLE-connected devices, one of which has a penchant to disconnect sporadically.

“When doing a connection in a BleakClient with a string address, the BleakClient dows a BLE Scan to ensure that that the device is seen by the backend system.” caught my eye. At https://github.com/hbldh/bleak/blob/develop/bleak/backends/bluezdbus/client.py#L56

def __init__(self, address_or_ble_device: Union[BLEDevice, str], **kwargs):

Does this mean that at least some of the two-device challenge can be avoided by doing a scan and passing the BLEDevice to the constructor?

(There will still be challenges as one of the interactions with the app is to change devices, on the fly.)

yes, be aware that this issue is only in Linux, on window it works fine connecting to 2 devices by string.

[hbldh]

I also wrote a more advanced, verbose two client script while debugging. Sharing that one as well, in case you or someone else might find it useful:

import sys
import asyncio
import logging
from typing import List

from bleak import BleakClient, BleakScanner
from bleak.backends.device import BLEDevice

logger = logging.getLogger("bleak.examples.two_devices")
handler = logging.StreamHandler(sys.stdout)
handler.setLevel(logging.DEBUG)
handler.setFormatter(
    logging.Formatter(fmt="%(asctime)-15s %(name)-8s %(levelname)s: %(message)s")
)
logger.addHandler(handler)
logger.setLevel(logging.DEBUG)


def callback(sender, data):
    print(sender, data)


async def run(addresses, notification_uuids):
    devices = await scan_for_devices(addresses)
    tasks = asyncio.gather(
        *(
            connect_to_device(device, n_uuid)
            for device, n_uuid in zip(devices, notification_uuids)
        )
    )
    await tasks


async def scan_for_devices(addresses: List[str]) -> List[BLEDevice]:
    addresses = [a.lower() for a in addresses]
    s = BleakScanner()
    logger.debug("Detecting devices...")
    devices = [await s.find_device_by_address(address) for address in addresses]
    for d in devices:
        if d:
            logger.debug(f"Detected {d}...")
    if None in devices:
        # We did not find all desired devices...
        undetected_devices = list(
            set(addresses).difference(
                list(
                    filter(
                        lambda x: x in [d.address.lower() for d in devices if d],
                        addresses,
                    )
                )
            )
        )
        raise ValueError(
            f"Could not find the following device(s): {undetected_devices}..."
        )
    return devices


async def connect_to_device(address: BLEDevice, notification_uuid: str):
    logger.info(f"Starting {address} loop...")
    async with BleakClient(address, timeout=20.0) as client:
        logger.info(f"Connected to {address}...")
        try:
            await client.start_notify(notification_uuid, callback)
            for i in range(10):
                r = await client.read_gatt_char("00002A25-0000-1000-8000-00805f9b34fb")
                logger.debug(f"[{address}] Serial Number String: {r}")
                await asyncio.sleep(6.0)
            await client.stop_notify(notification_uuid)
        except Exception as e:
            logger.error(e)
    logger.info(f"Disconnected to {address}...")


if __name__ == "__main__":
    loop = asyncio.get_event_loop()
    # Send a list of addresses to connect to and corresponding array of uuids to start notifications on.
    loop.run_until_complete(
        run(
            [
                "EF:A6:0D:2A:30:55",
                "24:71:89:CC:09:05"
            ],
            [
                "c9f60023-9f9b-fba4-5847-7fd701bf59f2",
                "0000{0:x}-0000-1000-8000-00805f9b34fb".format(0xFFE1),
            ],
        )
    )