Firewall

Show listening ports 
 # Show all listening TCP ports with process names
sudo ss -tlnp

# Show all listening UDP ports with process names
sudo ss -ulnp

# Show both TCP and UDP listening ports
sudo ss -tulnp
 
 Enable ssh (it it on 22 port) 
 sudo ufw allow ssh
sudo ufw allow OpenSSH
sudo ufw allow 22/tcp

 
 Enable firewall 
 sudo ufw enable