Brief story:
I forked from https://github.com/lus-robotics/cputemp who forked from https://github.com/Douglas6/cputemp. The latter made a nice wrapper around bluez dbus for use on RPi and the former made a python module out of it.
Why not take it one step further and make it a library module? This is what I'm doing now :)
Content below is yet to be changed!
Python GATT server example for the Raspberry Pi
Copyright (c) 2019, Douglas Otwell
Distributed under the MIT license http://opensource.org/licenses/MIT
As of BlueZ version 5.43 (currently shipped with Raspbian Stretch), some BLE aspects are still experimental. You will need to add the 'Experimental' flag to the bluetooth daemon. Do this: sudo nano /etc/systemd/system/dbus-org.bluez.service and add the '-E' flag at the end of the 'ExecStart' line. It should look like this:
ExecStart=/usr/lib/bluetooth/bluetoothd -E
Save the file and reboot.
git clone https://github.com/douglas6/cputemp.git
cd cputemp
python3 cputemp.py
The server should by accessable by any BLE client; I like to use the 'nRF Connect' app on my Android phone.
The service (UUID 00000001-710e-4a5b-8d75-3e5b444b3c3f) provides two characteristics:
UUID 00000002-710e-4a5b-8d75-3e5b444b3c3f: a read/notify characteristic representing the Pi's CPU temperature as a string.
UUID 00000003-710e-4a5b-8d75-3e5b444b3c3f: a read/write characteristic indicating the units to use to display the temperature; 'F' or 'C'.