The master branch of OnStep (version 3.0h) now has support for communicating with it over WiFi.
If your controller has a WiFi module, you need to re-flash that module with the WiFi-Bluetooth addon from the above version.
The difference is that you use port 9998, but keep using 9999 for the Android App as usual.
For INDI, you can change that under the Connect tab.
This was tested with Stellarium Mobile Plus and found to be working.