Based on this answer, blocking port 67 UDP outgoing should be
firewall-cmd --permanent --direct --add-rule ipv4 filter OUTPUT 0 -p udp -m udp --dport=67 -j ACCEPT
firewall-cmd --permanent --direct --add-rule ipv4 filter OUTPUT 1 -j DROP
firewall-cmd --reload
Port 67 UDP is the port a DHCP server uses, so I would like to verify that the port is indeed blocked before I start the DHCP server, so I can experiment with it in a sandbox.
Question
Since it is UDP and below 1024, how can I comfirm it is blocked?