SHELL

linux get port usage

# Linux (tested on Kali & Ubuntu)
sudo ss -tulpn | grep LISTEN

used port linux

# Linux
ss -ltn

# windows
netstat -a -p -n tcp | findstr LISTENING

# SOURCE 
https://solace.community/discussion/26/how-to-find-a-free-tcp-port-for-testing-pubsub-with-docker