1) Rule for allowing port 2408 in IP block 103.21.244.0/22 is as below:
firewall-cmd --permanent --zone=public --add-rich-rule='rule family="ipv4" source address="103.21.244.0/22" port protocol="tcp" port="2408" accept'
2) Allow port 443 for all IP's
firewall-cmd --permanent --zone=public --add-port=443/tcp
3) Reload firewall
firewall-cmd --reload
4) List all firewall rules
firewall-cmd --list-all