@IntRange(from = 23, to = 517)
	protected int getMtu() {
		return requestHandler.getMtu();
	}
Returns the current MTU (Maximum Transfer Unit). MTU specifies the maximum number of bytes
that can be sent in a single write operation. 3 bytes are used for internal purposes,
so the maximum size is MTU-3. The value will changed only if requested with
{@link #requestMtu(int)} and a successful callback is received. If the peripheral requests
MTU change, the {@link BluetoothGattCallback#onMtuChanged(BluetoothGatt, int, int)}
callback is not invoked, therefor the returned MTU value will not be correct.
Use {@link android.bluetooth.BluetoothGattServerCallback#onMtuChanged(BluetoothDevice, int)}
to get the callback with right value requested from the peripheral side.

@return the current MTU value. Default to 23.
ble/src/main/java/no/nordicsemi/android/ble/BleManager.java