Firewalld - Ports - /etc/services

English Applications
1

Hello.
Question
If you make your own /etc/services files by modifying and/or add new ports. Applications are supposed uses theses ports ( from my /etc/services ).
My /etc/services Examples


.........
.........
ftp                21/sctp      # FTP  [Randall_Stewart] [RFC4960]
ssh                22/sctp      # SSH  [Randall_Stewart] [RFC4960]
#ssh                   22/tcp       # The Secure Shell (SSH) Protocol  [RFC4251]
#ssh                   22/udp       # The Secure Shell (SSH) Protocol  [RFC4251]
#telnet                23/tcp      # Telnet  [Jon_Postel] [RFC854]
#telnet                23/udp      # Telnet  [Jon_Postel] [RFC854]
#                  24/tcp       any private mail system  [Rick_Adams]
.........
.........
#
ssh             12345/tcp       # [JCD] - The Secure Shell (SSH) Protocol  [RFC4251]
ssh             12345/udp       # [JCD] - The Secure Shell (SSH) Protocol  [RFC4251]
.........
.........
#
telnet          23456/tcp       # [JCD] - The Secure Shell (SSH) Protocol  [RFC4251]
telnet          23456/udp       # [JCD] - The Secure Shell (SSH) Protocol  [RFC4251]
#
#

I may connect with ssh from my computer to myself on the same computer.
But I was not able to connect from another computer on the local network.
(No change in the initial configuration of firewalld)
I have to add the port manually

firewall-cmd --zone=public --add-port=12345/tcp --permanent
firewall-cmd --zone=public --add-port=12345/udp --permanent
firewall-cmd --reload

A reboot was necessary ??

Any comments are welcome.

2

“/etc/services” is of limited use. It cannot be trusted and few services use it actively.

The listening IP addresses and ports for sshd are defined in “/etc/ssh/sshd_config”.

After modifying “/etc/ssh/sshd_config” restart sshd.

# systemctl restart sshd

Firewalld enables you to change running and permanent rules.

3

You’ve completely misunderstood what /etc/services file is - it’s simply a list of services that may be used on the computer, a sort of a catalogue that applications can use to lookup what service might be running on a port.

Changing the numbers on this file does not activate, move or otherwise manipulate any services and you should not change this file at all apart from very explicit situations.

4

Thank you every body for helping