flvstreamer software package provides command-line RTMP client, 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 flvstreamer
flvstreamer is installed in your system.
Make ensure the flvstreamer package were installed using the commands given below,
$ sudo dpkg-query -l | grep flvstreamer *
You will get with flvstreamer package name, version, architecture and description in a table
| Distro | Debian 9 stretch |
| Section | Utilities |
| Package | flvstreamer |
| Version | 2.1c1-1+b1 [armhf], 2.1c1-1 [a |
| Description | command-line RTMP client |
| Sub Section | Utils |