Traccar and its commands.
You can check it in the source code.
An example of this is the Teltonika decoder in Traccar:
https://github.com/traccar/traccar/blob/master/src/main/java/org/traccar/protocol/TeltonikaProtocolDecoder.java
I think better example is a protocol file, which tells you which commands are supported:
Traccar has its own set of commands but I had to use custom commands for some devices and it had me thinking.
Is there somewhere to find which devices will work with traccar internal commands? So there's no need to become crazy finding out by trial and error with every device.