I wanted to see on what ports my ubuntu machine was listening on; therefore, I ran the command netstat -tulpn.
When I ran that command I found out that I was listening on port 4569.
That is being used by Asterisk. Since I do not plan to use the IAX protocol and only stick to SIP, how can I disable IAX so that my computer stops listening on that port?
Maybe I have to enter disabled=true at /etc/asterisk/sip.conf ?
Finally I found the solution. The list of all the modules that asterisk loads can be found in here:
https://www.voip-info.org/wiki/view/Asterisk+modules
In my case I did not wanted to load the IAX modules since I do not use it. I added this lines:
noload => chan_iax.so
noload => chan_iax2.so
to /etc/asterisk/modules.conf
then restarted asterisk:
asterisk -rx 'core restart gracefully'
after asterisk reloaded I can see that port 4569 no longer shows up when running netstat -tulpn.