My Centos7 firewalld has TCP ports 8083, 8086, and 5000 open. I don't recall opening them, except for maybe 5000 when first learning about firewalld.
Are there any ports that might come out of the box open? If not, can you think of anything in common with these mystery ports?
My CentOS 7 apparently came with ports 10010-10020/tcp, and services ssh and dhcpv6 open on the public zone, the default active zone.
You should specify which zone you are asking about, as there are 9 predefined zones, as of v.0.6
8083 and 8086 are both used by ITunes, according to this source.
One of the first tasks when setting up a server connected to the internet is to configure the firewall. In my case, for example, it was a VPS that should only be accessed from my home network, so I activated and opened the home zone to my local network IPs, and closed the (default) public zone to everything, loosely following this guide.
