@Override
        protected void onServicesInvalidated() {
            // This is not needed anymore because this issue was fixed in 2.5 ble library
            // We reset the MTU to 23 upon disconnection
            // overrideMtu(MTU_SIZE_DEFAULT);
            mIsDeviceReady = false;
            isProvisioningComplete = false;
            mMeshProvisioningDataInCharacteristic = null;
            mMeshProvisioningDataOutCharacteristic = null;
            mMeshProxyDataInCharacteristic = null;
            mMeshProxyDataOutCharacteristic = null;
        }
BluetoothGatt callbacks for connection/disconnection, service discovery, receiving notifications, etc.
app/src/main/java/no/nordicsemi/android/nrfmesh/ble/BleMeshManager.java