knockd software package provides small port-knock daemon, you can install in your Debian 8 (Jessie) by running the commands given below on the terminal,
$ sudo apt-get update $ sudo apt-get install knockd
knockd is installed in your system.
Make ensure the knockd package were installed using the commands given below,
$ sudo dpkg-query -l | grep knockd *
You will get with knockd package name, version, architecture and description in a table
| Distro | Debian 8 jessie |
| Section | Network |
| Package | knockd |
| Version | 0.5-3 |
| Description | small port-knock daemon |
| Sub Section | Net |