Enable the firewalld service:

# systemctl enable firewalld

Starting the firewalld service:

# systemctl start firewalld

Verifying that firewalld service is running:

# firewall-cmd --state

Checking the firewall default zone:

# firewall-cmd --get-default-zone

Opening a ports and service:

# firewall-cmd --zone=public --permanent --add-port=22222/tcp
# firewall-cmd --zone=public --permanent --add-service=ssh

Restarting the firewalld service:

# systemctl restart firewalld

Verifying open ports and services:

# firewall-cmd --list-all
public (default, active)
  interfaces: enp0s25
  services: dhcpv6-client ipp ipp-client mdns ssh
  ports: 22222/tcp
  masquerade: no
  rich rules: 


Also add the port that you opened  to semanage if you have it running.

# semanage port -a -t ssh_port_t -p tcp 22222