and since it's UDP, if it's lost it's lost. and since it's not standard http/JSON, nobody will have a clue in a year and can't decode it.

to learn and play with it it's fine, else why complicate life?

Using protobuf is practical enough in embedded. This person isn't the first and won't be the last. Way faster than JSON, way slower than C structs.

However protobuf is ridiculously interchangeable and there are serializers for every language. So you can get your interfaces fleshed out early in a project without having to worry that someone will have a hard time ingesting it later on.

Yes it's a pain how an empty array is a valid instance of every message type, but at least the fields that you remember to send are strongly typed. And field optionality gives you a fighting chance that your software can still speak to the unit that hasn't been updated in the field for the last five years.

On the embedded side, nanopb has worked well for us. I'm not missing having to hand maintain ad-hoc command parsers on the embedded side, nor working around quirks and bugs of those parsers on the desktop side