Carla network protocol information

I’m looking for information on the carla server network protocol. The documentation page appears to be out of date. https://carla.readthedocs.io/en/stable/carla_server/

  1. It refers to a C-API and links to a file that does not exist
  2. It mentions three ports (world, world + 1, world + 2) but when I run carla I can only connect socket to (world) and (world + 1)
  3. It mentions a 32bit size header followed by protocol buffers, but the repo doesn’t appear to contain any protocol buffer message descriptions. The code in LibCarla appears to use messagepack so I’m guessing the serialization format is messagepack?

If someone has a few moments to provide some basic information about the network protocol I would greatly appreciate it. Things like:

  1. wire protocol
  2. serialization format
  3. port semantics

Thanks!