bluez software package provides Bluetooth tools and daemons, you can install in your Debian 9 (Stretch) by running the commands given below on the terminal,
$ sudo apt-get update $ sudo apt-get install bluez
bluez is installed in your system.
Make ensure the bluez package were installed using the commands given below,
$ sudo dpkg-query -l | grep bluez *
You will get with bluez package name, version, architecture and description in a table
| Distro | Debian 9 stretch |
| Section | Administration Utilities |
| Package | bluez |
| Version | 5.23-2+b1 |
| Description | Bluetooth tools and daemons |
| Sub Section | admin |