How to enable and use firewall management on CentOS/RHEL/Fedora/Docker (firewall-cmd)

Firewalld is daemon for management of IP filtering (firewalling) rules based on iptables.

How to install and enable it:

sudo yum install firewalld
sudo systemctl enable firewalld
sudo systemctl start firewalld

This tool can be used for simple opening or protecting TCP/UDP ports, or more detailed/sophisticated whitelisting or blacklisting via rich rules (based not only on TCP/UDP ports, but also source or destination IP address, etc.), on Linux system, and various other IP filtering configurations.

More detailed information can be found e.g. in this article from Mark Cunningham.