Please elaborate, what exactly you are talking about
There is no need for any libraries
are you working with bluetooth classic or BLE?
there is the bluetooth client and server component available for bluetooth classic
https://ai2.appinventor.mit.edu/reference/components/connectivity.html#BluetoothClient
https://ai2.appinventor.mit.edu/reference/components/connectivity.html#BluetoothServer
and the BLE extension
Taifun