RHEL/firewalld

Add Port

firewall-cmd --add-port=80/tcp --permanent
firewall-cmd --reload

Firewall

Show running status:

systemctl status firewalld
# or
firewall-cmd --state

Show open services (and associated ports):

firewall-cmd --get-services
# cockpit dhcpv6-client http https ssh

Show explicit ports added:

firewall-cmd --list-ports

Open ports now (temporary):

firewall-cmd --zone=public --add-service=http
firewall-cmd --zone=public --add-service=https

Add specific port:

firewall-cmd --zone=public --add-port=27000/tcp  # flexlm lmgrd service

ref: [1]

--

Open ports now (temporary):

firewall-cmd --zone=public --add-service=http
firewall-cmd --zone=public --add-service=https
firewall-cmd --zone=public --add-port=27000/tcp  # lmgrd

Add to startup script (persistent - does not alos open):

firewall-cmd --zone=public --add-service=http --permanent
firewall-cmd --zone=public --add-service=https --permanent
firewall-cmd --zone=public --add-port=27000/tcp --permanent  # lmgrd

If you didn't use the --permanent, to save:

firewall-cmd --runtime-to-permanent

ref: [2]