On my Arduino code it can not lie, I already asked in the appropriate forum.
The error can only be the API.
In the Arduino code to read enough "int c = Serial2.read ();" and to write "Serial2.write (c);", because you can not go wrong.
And as already written, read works.
It's strange you can't read. Can you give us a screen capture with Android, and for example, the nrf master control panel of nordic? i've my own BT device and the characteristic has read and notify attrib, so you can use read and notify.
I would like notifications in both b4a and b4i !!!