[BLE] Subscription/Notification does not work

[ThumbGen]

Please check all of the platforms you are having the issue on (if platform is not listed, it is not supported)

• iOS
• [ X] Android
• UWP
• .NET Standard

Feature Library

• Core
• [ X] BluetoothLE
• Locations
• HTTP Transfers
• Notifications
• Sensors

Version of OS(s) listed above with issue

Android 8.0

Version of Library

1.0.0.244-beta

Expected Behavior

Subscribing to notifications should work.

Actual Behavior

None of the 3 GATT clients I've tried is able to subscribe to the "notifiable" characteristics offered by a Shiny GATT server.

The problem is reproducible with the latest Shiny-Samples project too (I saw there are notifications there too).

[aritchie]

Please file a reproducible case where possible. This is still in beta, so I need help, not just issues. The GATT server is not completed fully yet obviously.

[ThumbGen]

The best case possible is your own excellent Samples project:

In Sample.BlePeripherals.MainViewModel, there's

                            this.notifications = sb.AddCharacteristic
                            (
                                NotifyCharacteristicUuid,
                                cb => cb.SetNotification(cs =>
                                {
                                    var subs = cs.Characteristic.SubscribedCentrals.Count;

                                    var @event = cs.IsSubscribing ? "Subscribed" : "Unsubcribed";
                                    this.Write($"Device {cs.Peripheral.Uuid} {@event}");
                                    this.Write($"Charcteristic Subcribers: {subs}");

                                    if (subs == 0)
                                        this.StopTimer();
                                    else
                                        this.StartTimer();
                                })
                            );

Using the "Bluetooth LE Explorer" app from Windows Store I've managed to list the characteristic, it is correctly displayed as "notifiable", but attempting to subscribe to it fails. The code inside the "SetNotification" subscription handler is never called.

[fryette]

I also experienced this issue, but in my case it was incorrect configuration for device which advertise characteristic. Check is it everything OK with nrfConnect application(check it on iOS and Android store), and if even nrfConnect fail -something wrong with your BLE configuration

[ThumbGen]

I have just tried the ACR Bluetooth LE app and the problem exists there too (other apps like BLE Sim work correctly).

Reading https://stackoverflow.com/questions/17910322/android-ble-api-gatt-notification-not-received
I've noticed this sentence:

"All of the writeGattDescriptors must come first and complete before you issue any readCharacteristic calls."

No idea, I thought this might help...

[aritchie]

@ThumbGen Did you try anything from the link you provided?

[aritchie]

This is working fine for me using iOS nrf connect to android shiny gatt server running in the sample app. Was there an exception? Anything in the output window.

[ThumbGen]

Sorry for the delayed reply, indeed it was a problem on my side.
I had to add the CCCD flag with notifications on the subscriber side; now the notifications are working and are absolutely awesome!

Thank you!

[lock]

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