firewalld Command Builder
Enter source IP, source port, protcol, and action.
Source IP can be a single address (i.e. 192.0.2.25) or an range (i.e. 192.0.2.0/24).
Source port can be a single number (i.e. 22) or a range (i.e. 20-23).
firewall-cmd --reload
Verify firewall rules with these commands:
iptables -S IN_public_allow
iptables -S IN_public_deny
Further Reading:
https://en.wikipedia.org/wiki/List_of_TCP_and_UDP_port_numbers