@Juan_Antonio I can't get that Circuit Digest example to work (even after I added () to the prints so the codes is Python 3). The Pi code has never got past server_socket.accept() despite much mucking about on my Android phone. (The Bluetooth terminal program mentioned by Circuit Digest doesn't seem to work on my phone; at least, I haven't found any way of telling it which Bluetooth device to connect to. I've tried a couple of other Bluetooth terminal programs, but they can't connect to my Pi.)
I've got an App Inventor app which happily displays a list of paired devices using
If I tap on "B8:27:EB:14:9D:19 RPi0W" (which is the Pi running the Circuit Digest Python code), my code does
which pops up an error message (which disappears frustratingly quickly) that says "Error 507: Unable to connect. Is the device turned on?" (It is, and waiting for a connection.)
@sjoerd1953 I'm sorry, but most of that is over my head!
Does anyone know of any other descriptions of how to connect App Inventor to Raspberry Pi?