How to organize a closed bluetooth network?

Question

Arduino

There are many identical devices (microcontroller with bluetooth). How to organize a network between them so that it is not visible from the outside and devices connect only to devices on this network, and not to any visible ones?

Answer 1

No way. In any case, the BT device must be either a server or a client. Bluetooth is point to point. For network look at something like nRF24

Answer 2

The Bluetooth network must have one master device and can have up to 7 slaves. All devices have a MAC address that must be used in the controller firmware to identify specific BT devices.