Lighting
Neither of the block update-related packets, Set Block or Set Multiple Blocks, contain lighting information. As such, lighting cannot be updated directly, and is instead calulated on the client as blocks are placed or broken.
This is done for two reasons.
- Sending multiple block updates just to update lighting data would be incredible wasteful from a bandwidth usage perspective
- Since the client uses the exact same lighting engine, the resulting lighting should be the exact same
The only exception to the "no lighting data" rule is the chunk packet, which comes with the full chunk data, including lighting.