I have added two rules in firewalld, using the following commands:firewall-cmd --zone=public --add-port=22005/tcp --permanentfirewall-cmd --zone=public --add-port=22003/udp --permanentAfter reloading firewalld, I took a look at iptables, with iptables -LACCEPT     tcp  --  anywhere             anywhere             tcp dpt:optohost005 ctstate NEWACCEPT     udp  --  anywhere             anywhere             udp dpt:optohost003 ctstate NEWWhat is optohost, and why does it replace 22? I can't find much about this anywhere on Google. It only seems to happen for these two IPs (22005/22003) I am running CentOS Linux release 7.3.1611, 3.10.0-514.26.2.el7.x86_64firewalld 0.4.3.2Update:After some more searching, I found this: http://sysconfcollect.sourceforge.net/examples/scc.docker_centos7.htmloptohost003     22003/tcp               # Opto Host Port 3optohost003     22003/udp               # Opto Host Port 3optohost005     22005/tcp               # Opto Host Port 5optohost005     22005/udp               # Opto Host Port 5This is documentation for docker, more specifically the contents of /etc/services which I checked manually on my machine and the lines exist. I'm not exactly sure what docker does but I know it's something to do with my network.. If I check ifconfig, sure enough it's there:docker0: flags=4099<UP,BROADCAST,MULTICAST>  mtu 1500    inet 172.17.0.1  netmask 255.255.0.0  broadcast 0.0.0.0    ether 02:42:d2:8b:6d:b6  txqueuelen 0  (Ethernet)    RX packets 0  bytes 0 (0.0 B)    RX errors 0  dropped 0  overruns 0  frame 0    TX packets 0  bytes 0 (0.0 B)    TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0What I gather from this is that docker has some services running on those ports (22005/22003) and it's taking over (?)I need these ports for a game server that I run. Any idea on how to stop it from taking over those ports?Update #2: Removing those lines from /etc/services makes optohost disappear when looking up the ports with iptables -L, and the ports are displayed correctly. However I am not entirely sure what effect removing those lines has, and if it has any actual effect at all apart from simply being a label or name.
How to stop Opto Host taking over a port (Linux)
centos;firewalld