To pair two Bluetooth dongle, one of them needs to be configured as Central and other needs to be configured as Peripheral. We already wrote a Python script that sends data back and forth between dongles.
In short :

One dongle will take on the Central role and the other will take on the Peripheral role.
Then they will connect to each other.
The Central dongle will then start off sending a message; "Echo".
The Peripheral dongle will then receive the message and send it back to the Central dongle which in turn will receive it and send it back and so forth until the script is stopped.
Device Required:
Laptop
2 BleuIO - BLE Dongle

Software Tools Required :
Tera Term
Python
Follow the instructable
https://www.instructables.com/Sending-and-Receiving-Data-Between-Two-Bleutooth-D/