Notification stream of characteristic doesnt work

[vovagorodok]

characteristicRx.readValue() and characteristicTx.writeValue(data, type: BlueZGattCharacteristicWriteType.command); works correctly on Central. Peripheral (Arduino) device receives write without response and notifies on characteristicRx, but nothing happens on propertiesChanged stream (waiting 5 seconds).

await characteristicRx.startNotify();
_subscription = characteristicRx.propertiesChanged
    .where((properties) => properties.contains('Value'))
    .listen((properties) {
  print("Received data: ${characteristic.value}");
});
print("Is notifying: ${characteristic.notifying}");

Only print Is notifying: false is visible.
Not sure if I'm doing something wrong. Can't find example of characteristic notification receiving.
Code that I'm working on: https://github.com/vovagorodok/ble_backends/blob/main/packages/bluez_backend/lib/bluez_characteristic.dart

[jefflongo]

Have you tried making sure on the Arduino side the notification is getting sent? My project uses the exact same method for listening for notifications (well I subscribe first then call startNotify) and it works just fine.

[vovagorodok]

Have you tried making sure on the Arduino side the notification is getting sent?

Yes, checking on debug/serial logs. I am working on BLE libraries wrapper in order to easily swap between libraries in my app. Wrapper works correctly with flutter_reactive_ble, flutter_web_bluetooth, win_ble...

My project uses the exact same method for listening for notifications (well I subscribe first then call startNotify) and it works just fine.

Changing order of subscribe and startNotify doesn't help. I'm on latest Fedora. What distro do you have?

[jefflongo]

I'm using Ubuntu 24.04. Could be worth monitoring btmon and check the logs there.

[vovagorodok]

Captured only moment where we write without response Data[5]: 10804f0900 and waiting for notification Data[9]: 00ef00000000000000:

$ sudo btmon
Bluetooth monitor ver 5.78
btmon[89032]: = Note: Linux version 6.10.12-200.fc40.x86_64 (x86_64)                                                                                                                                                                 0.318844
btmon[89032]: = Note: Bluetooth subsystem version 2.22                                                                                                                                                                               0.318847
= New Index: F8:AC:65:DE:85:5E (Primary,USB,hci0)                                                                                                                                                                             [hci0] 0.318848
= Open Index: F8:AC:65:DE:85:5E                                                                                                                                                                                               [hci0] 0.318848
= Index Info: F8:AC:65:DE:85:5E (Intel Corp.)                                                                                                                                                                                 [hci0] 0.318849
bluetoothd[2254]: @ MGMT Open: bluetoothd (privileged) version 1.22                                                                                                                                                         {0x0001} 0.318850
bluetoothd[2254]: < ACL Data TX: Handle 3585 flags 0x00 dlen 9                                                                                                                                                            #1 [hci0] 54.414528
      ATT: Write Request (0x12) len 4
        Handle: 0x000f
          Data[2]: 0100
> HCI Event: Number of Completed Packets (0x13) plen 5                                                                                                                                                                    #2 [hci0] 54.429210
        Num handles: 1
        Handle: 3585
        Count: 1
> ACL Data RX: Handle 3585 flags 0x02 dlen 5                                                                                                                                                                              #3 [hci0] 54.475752
      ATT: Write Response (0x13) len 0
bluetoothd[2254]: < ACL Data TX: Handle 3585 flags 0x00 dlen 12                                                                                                                                                           #4 [hci0] 54.482542
      ATT: Write Command (0x52) len 7
        Handle: 0x000c
          Data[5]: 10804f0900
> HCI Event: Number of Completed Packets (0x13) plen 5                                                                                                                                                                    #5 [hci0] 54.519211
        Num handles: 1
        Handle: 3585
        Count: 1
> ACL Data RX: Handle 3585 flags 0x02 dlen 16                                                                                                                                                                             #6 [hci0] 54.565747
      ATT: Handle Value Notification (0x1b) len 11
        Handle: 0x000e
          Data[9]: 00ef00000000000000

Looks that we receive expected data from peripheral, but buez library doesn't notify us, some issue on systemd level?

[vovagorodok]

Also checked the same functionality on python bleak library: https://github.com/vovagorodok/ArduinoBleOTA/blob/main/tools/uploader.py
And looks that it works correctly, we receive notification and start uploading

[vovagorodok]

@dkwach checked identical functionality with bluez.dart on his Ubuntu 24.04. And it works correctly and Data[9]: 00ef00000000000000 was notified. Looks that it's some issue with Fedora 40 + bluez.dart