Dear Sebastián,
Welcome to the list.
- Does exist a command to test connection (eg. ping or echo)?
Not really. Instead, you can try to register a client. If you get a response, the connection is available.
- Can I trust in error message text for detecting error conditions?
The returned result code of commands (00: ok, 01: error) indicates an operation was successful [1]. It depends on the specific command or query which error messages will be returned.
Hope this helps, Christian