Ngrep (network grep) is a simple yet powerful network packet analyzer.

sudo apt install ngrep
sudo yum install ngrep
sudo dnf install ngrep

Usage :

ngrep port 25
ngrep -d any 'error' port 514
...

FREE active monitoring companion

< alternative to Pingdom, Uptime Robot, StatusCake or !nsping >

A tester.

Avec https://pomfe.co & http://www.hnng.moe

Sources :

• Uguu : https://github.com/nokonoko/uguu
• Hnng : https://github.com/Francesco149/hnng-moe
• Pomfe : https://github.com/Pomfe/pomfe.co

Simple monitoring tools.
Avec https://www.tecmint.com/command-line-tools-to-monitor-linux-performance/

A simple, focused eBook reader