Thanks for the steer.
Implemented serialized data, i.e. objects, sent from B4A to B4R via BLE = Working fine.
The other way around, i.e. B4R to B4A using asyncstream write is also working =requires manager.setnotify.
Background
Working on a LEGO Showcase to remote control LEGO trains (via B4A) and accessories (via B4R with connected IO devices) using BLE.
The B4A client to control up-to3 LEGO trains is done (PUTrains). Developed and tested a B4XLib to control LEGO hubs, like movehub, powered-up.
Next working on setting the state of the railroad switch points using servo motors. Thereafter other sensors like rfid, led's etc...
Will share more info whilst making progress.
B4A App- running the green train forward at speed 40 - live data.
B4R - Prototype of a LEGO city switch track (#53407) with (strong) servo motor (HS-311) controlled by an Arduino MEGA with BLE HM-10 module.
The LEGO touch sensor (#9843) enables to switch as well. Testing using a B4A app.
Note: The Arduino motor shield on the MEGA is not required and has been used to test other solutions like a LEGO NXT or Power Functions motor.
BTW: someone is watching