linux check if firewall is running ports code example

Example 1: ubuntu check process on port

sudo lsof -i:22

Example 2: how to check list of open ports in linux

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