https://en.wikipedia.org/wiki/Firewalld
“firewalld is a firewall management tool for Linux operating systems. It provides firewall features by acting as a front-end for the Linux kernel's netfilter framework. firewalld's current default backend is nftables. Prior to v0.6.0, iptables was the default backend.Through its abstractions, firewalld acts as an alternative to nft and iptables command line programs.”
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public (active)
target: default
icmp-block-inversion: no
interfaces: enp0s3
sources:
services: dhcpv6-client ssh
ports: 2212/tcp <-- there may be none, several, or many here
protocols:
masquerade: no
forward-ports:
source-ports:
icmp-blocks:
rich rules: |
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sudo firewall-cmd --add-port=2212<port id, eg 2212>/tcp |
Consult the firewalld documentation for details on how firewalld (and iptables) operates and for additional commands to reverse changes made, to make additional changes, or to disable firewalld enforcement.