coturn software package provides TURN and STUN server for VoIP, 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 coturn
coturn is installed in your system.
Make ensure the coturn package were installed using the commands given below,
$ sudo dpkg-query -l | grep coturn *
You will get with coturn package name, version, architecture and description in a table
| Distro | Debian 9 stretch |
| Section | Network |
| Package | coturn |
| Version | 4.5.0.5-1 |
| Description | TURN and STUN server for VoIP |
| Sub Section | Net |