command show used port code example
Example 1: linux how to see ports in use
# Any of the following
sudo lsof -i -P -n | grep LISTEN
sudo netstat -tulpn | grep LISTEN
sudo lsof -i:22 # see a specific port such as 22
sudo nmap -sTU -O IP-address-Here
Example 2: cmd listening ports
C:\> netstat -a -b