How to check listening ports on CentOS

Sometimes you need to know what your server is serving.

That is, what applications or programs are running on the server that are accessed over the network and what port are they listening on.

I’m used to netstat on Windows, lets give that a try

[root@homeserver hassconfig]# netstat -a
-bash: netstat: command not found

OK, so lets

https://www.google.com/search?q=centos+netstat

Which first result gives me

https://unix.stackexchange.com/questions/146190/commands-not-found-netstat-nmap-on-centos-7

It seems on CentOS7 the classic netstat has been replaced by the iproute2 suite. Thanks slm.

So we now have a list of CentOS 7 networking commands

Deprecated Linux networking commands and their replacements

How to view just listening ports using ss

https://www.google.com/search?q=ss+listening+ports

which gives me

https://www.linux.com/learn/intro-to-linux/2017/7/introduction-ss-command

And in the excellent article i can see the command i need

[root@homeserver hassconfig]# ss -4 state listening
Netid Recv-Q Send-Q                                                                          Local Address:Port                                                                                           Peer Address:Port
tcp   0      128                                                                                         *:8123                                                                                                      *:*
tcp   0      50                                                                                          *:microsoft-ds                                                                                              *:*
tcp   0      50                                                                                          *:netbios-ssn                                                                                               *:*
tcp   0      128                                                                                         *:ssh                                                                                                       *:*
tcp   0      100                                                                                 127.0.0.1:smtp                                                                                                      *:*

This tells me on IPv4 my server is listening on ports 8123, 445 (microsoft-ds), 139 (netbios-ssn), 22 (ssh) and (probably) 25 (smtp) on the loopback interface.