What is the COM port of serial port for Bluetooth for Raspberry Pi

I only use Windows (and Linux at occasion) and have no experience at all with a Raspberry Pi.

What is the output of printArray(Serial.list());? Did you try the different ports that are listed?

That would pick the first serial port. If I run it on Windows, it will pick COM1 which is a serial port that is by default available on my Win10 system and it will not be the Bluetooth port.