OK, I didn’t know that MusicCast devices can be also controlled with AV Controller app. I have it for an amplituner without musiccast. Sniffing the network works for it, I’ve created a couple controls and sensors this way but not for the arrows or enter button.
This app uses a different API and actually there has been some work done already to get the required commands. Have a look at this repo, I think it already includes the cursor and enter commands: