The “What’s in a LIFX message” documentation states:
The target field represents the MAC address of the device. This is also known as the device’s serial and appears as a hex number of the form
d073d5xxxxxx. When you address a device you should left-justify the first 6 bytes of the
targetfield with the MAC address and then zero-fill the last two bytes. You should set this value to all zero’s if you want to broadcast a message to the network.
The replies you get back from devices will always contain the MAC address of the device sending the reply. So for example if you are discovering devices, the StateService (3) message will tell you the serial for each LIFX device on your network.
With firmware 3.70 and higher, the serial of the device is no longer the same as the MAC address of the device, so this needs to change.