Yup, it should be possible. Here’s connection using both telnet and NC. You can interact with the firmware the same way, by sending normal g-code or system commands.
I’m just using the configured port ($305, default) and IP address ($302, default)
@KGN Thanks. It wasn’t working with PuTTY. But your response confirmed that it should work. So after more fiddling, a light bulb came on. I have gSender open and the controller may not accept more than one connection. Closed it and success connecting!