Listening Ports

  1. Find Out What Ports Are Listening / Open On My Linux & FreeBSD Server
  2. Various Ways to List Ports on Linux. Option #2 works on barebones machine.

Option #2 for barebones machine:

sudo ss -lntu

Port Binding

Applies to: “Ubuntu 16.04 LTS”

Ubuntu 16 Linux uses authbind application to control which non-root users can bind on <1000 port numbers.

Use the following procedure to add new application-port registration.

Example is for port 443 and Jenkins server:

sudo apt-get authbind

sudo touch /etc/authbind/byport/443
sudo chmod 500 /etc/authbind/byport/443
sudo chown jenkins /etc/authbind/byport/443