example if the zone is `public`, use ```sh firewall-cmd --zone=public --add-port=9000/tcp --permanent ``` Note that `permanent` makes sure the rules are persistent across firewall start, restart or reload. Finally reload the firewall for changes to take effect. ```sh firewall-cmd --reload ``` ### iptables For hosts with iptables enabled (RHEL, CentOS, etc), you can use `iptables` command to enable all traffic coming to specific ports. Use below command to allow access to port 9000 ```sh iptables -A...