Descriptor is empty for characteristics

Question

I have made a simple arduino code, where there are 6 characteristics, I have made a flutter apk where I observe all the characteristics which I defined in the arduino.

In setup code of arudino ->

    // Create the BLE Service
  BLEService* pService = pServer->createService(SERVICE_UUID);

  // Create a BLE Characteristic
  pCharacteristic1 = pService->createCharacteristic(
    CHARACTERISTIC_UUID1,
    BLECharacteristic::PROPERTY_READ | BLECharacteristic::PROPERTY_WRITE | BLECharacteristic::PROPERTY_NOTIFY | BLECharacteristic::PROPERTY_INDICATE);

  // Create a BLE Descriptor
  pCharacteristic1->addDescriptor(new BLE2902());


  // Create a BLE Characteristic
  pCharacteristic2 = pService->createCharacteristic(
    CHARACTERISTIC_UUID2,
    BLECharacteristic::PROPERTY_READ | BLECharacteristic::PROPERTY_WRITE | BLECharacteristic::PROPERTY_NOTIFY | BLECharacteristic::PROPERTY_INDICATE);

  // Create a BLE Descriptor
  pCharacteristic2->addDescriptor(new BLE2902());


  // Create a BLE Characteristic
  pCharacteristic3 = pService->createCharacteristic(
    CHARACTERISTIC_UUID3,
    BLECharacteristic::PROPERTY_READ | BLECharacteristic::PROPERTY_WRITE | BLECharacteristic::PROPERTY_NOTIFY | BLECharacteristic::PROPERTY_INDICATE);

  // Create a BLE Descriptor
  pCharacteristic3->addDescriptor(new BLE2902());

  // Create a BLE Characteristic
  pCharacteristic4 = pService->createCharacteristic(
    CHARACTERISTIC_UUID4,
    BLECharacteristic::PROPERTY_READ | BLECharacteristic::PROPERTY_WRITE | BLECharacteristic::PROPERTY_NOTIFY | BLECharacteristic::PROPERTY_INDICATE);

  // Create a BLE Descriptor
  pCharacteristic4->addDescriptor(new BLE2902());

  // Create a BLE Characteristic
  pCharacteristic5 = pService->createCharacteristic(
    CHARACTERISTIC_UUID5,
    BLECharacteristic::PROPERTY_READ | BLECharacteristic::PROPERTY_WRITE | BLECharacteristic::PROPERTY_NOTIFY | BLECharacteristic::PROPERTY_INDICATE);

  // Create a BLE Descriptor
  pCharacteristic5->addDescriptor(new BLE2902());


  // Create a BLE Characteristic
  pCharacteristic6 = pService->createCharacteristic(
    CHARACTERISTIC_UUID6,
    BLECharacteristic::PROPERTY_READ | BLECharacteristic::PROPERTY_WRITE | BLECharacteristic::PROPERTY_NOTIFY | BLECharacteristic::PROPERTY_INDICATE);

  // Create a BLE Descriptor
  pCharacteristic6->addDescriptor(new BLE2902());

And in loop of arudino->

// notify changed value
  if (deviceConnected) {
    pCharacteristic1->setValue((uint8_t*)&value, 4);
    pCharacteristic1->notify();
    
    pCharacteristic2->setValue((uint8_t*)&value, 4);
    pCharacteristic2->notify();
    
    pCharacteristic3->setValue((uint8_t*)&value, 4);
    pCharacteristic3->notify();
    
    pCharacteristic4->setValue((uint8_t*)&value, 4);
    pCharacteristic4->notify();
    
    pCharacteristic5->setValue((uint8_t*)&value, 4);
    pCharacteristic5->notify();
    
    pCharacteristic6->setValue((uint8_t*)&value, 4);
    pCharacteristic6->notify();
    value++;
    digitalWrite(2, HIGH);
    delay(1000);  // bluetooth stack will go into congestion, if too many packets are sent, in 6 hours test i was able to go as low as 3ms
  } else {

    digitalWrite(2, HIGH);  // Turn the LED on (HIGH is the voltage level)
    delay(2000);            // Wait for a second
    digitalWrite(2, LOW);   // Turn the LED off by making the voltage LOW
    delay(1000);
    }

Now in android logs i can find only 4 descriptor values, the characteristics 5 have empty descriptor and characteristics 6 was never found in the characteristics list

This is the log in android studio->

BluetoothCharacteristic{uuid: beb54831-36e1-4688-b7f5-ea07361b26a8, deviceId: C0:49:EF:CE:E7:E2, serviceUuid: 4fafc201-1fb5-459e-8fcc-c5c9c331914b, secondaryServiceUuid: null, properties: CharacteristicProperties{broadcast: false, read: true, writeWithoutResponse: false, write: true, notify: true, indicate: true, authenticatedSignedWrites: false, extendedProperties: false, notifyEncryptionRequired: false, indicateEncryptionRequired: false}, descriptors: [BluetoothDescriptor{uuid: 00002902-0000-1000-8000-00805f9b34fb, deviceId: C0:49:EF:CE:E7:E2, serviceUuid: 4fafc201-1fb5-459e-8fcc-c5c9c331914b, characteristicUuid: beb54831-36e1-4688-b7f5-ea07361b26a8, value: []}], value: []}

BluetoothCharacteristic{uuid: beb54832-36e1-4688-b7f5-ea07361b26a8, deviceId: C0:49:EF:CE:E7:E2, serviceUuid: 4fafc201-1fb5-459e-8fcc-c5c9c331914b, secondaryServiceUuid: null, properties: CharacteristicProperties{broadcast: false, read: true, writeWithoutResponse: false, write: true, notify: true, indicate: true, authenticatedSignedWrites: false, extendedProperties: false, notifyEncryptionRequired: false, indicateEncryptionRequired: false}, descriptors: [BluetoothDescriptor{uuid: 00002902-0000-1000-8000-00805f9b34fb, deviceId: C0:49:EF:CE:E7:E2, serviceUuid: 4fafc201-1fb5-459e-8fcc-c5c9c331914b, characteristicUuid: beb54832-36e1-4688-b7f5-ea07361b26a8, value: []}], value: []}

BluetoothCharacteristic{uuid: beb54833-36e1-4688-b7f5-ea07361b26a8, deviceId: C0:49:EF:CE:E7:E2, serviceUuid: 4fafc201-1fb5-459e-8fcc-c5c9c331914b, secondaryServiceUuid: null, properties: CharacteristicProperties{broadcast: false, read: true, writeWithoutResponse: false, write: true, notify: true, indicate: true, authenticatedSignedWrites: false, extendedProperties: false, notifyEncryptionRequired: false, indicateEncryptionRequired: false}, descriptors: [BluetoothDescriptor{uuid: 00002902-0000-1000-8000-00805f9b34fb, deviceId: C0:49:EF:CE:E7:E2, serviceUuid: 4fafc201-1fb5-459e-8fcc-c5c9c331914b, characteristicUuid: beb54833-36e1-4688-b7f5-ea07361b26a8, value: []}], value: []}

BluetoothCharacteristic{uuid: beb54834-36e1-4688-b7f5-ea07361b26a8, deviceId: C0:49:EF:CE:E7:E2, serviceUuid: 4fafc201-1fb5-459e-8fcc-c5c9c331914b, secondaryServiceUuid: null, properties: CharacteristicProperties{broadcast: false, read: true, writeWithoutResponse: false, write: true, notify: true, indicate: true, authenticatedSignedWrites: false, extendedProperties: false, notifyEncryptionRequired: false, indicateEncryptionRequired: false}, descriptors: [BluetoothDescriptor{uuid: 00002902-0000-1000-8000-00805f9b34fb, deviceId: C0:49:EF:CE:E7:E2, serviceUuid: 4fafc201-1fb5-459e-8fcc-c5c9c331914b, characteristicUuid: beb54834-36e1-4688-b7f5-ea07361b26a8, value: []}], value: []}

But for beb54835, there is no descriptor and beb54836 was not found in the characteristics.

BluetoothCharacteristic{uuid: beb54835-36e1-4688-b7f5-ea07361b26a8, deviceId: C0:49:EF:CE:E7:E2, serviceUuid: 4fafc201-1fb5-459e-8fcc-c5c9c331914b, secondaryServiceUuid: null, properties: CharacteristicProperties{broadcast: false, read: true, writeWithoutResponse: false, write: true, notify: true, indicate: true, authenticatedSignedWrites: false, extendedProperties: false, notifyEncryptionRequired: false, indicateEncryptionRequired: false}, descriptors: [], value: []}

Answer 1

Found that editing the numHandles solved the issue, by default only 15 numHandles was allowed

pService = pServer->createService(BLEUUID(SERVICE_UUID), 100);  // 100 handles