It is highly recommended that you have a firewall protecting your server.
These instructions are intended specifically for enabling and starting Firewalld on CentOS 7.
#enable firewall to load on startup
systemctl enable firewalld
#start the firewall service
systemctl start firewalld
To check the status of firewalld, run the following command as root:
systemctl status firewalld
Now you are ready to start creating firewalld rules.