If you host your server on echonode you will probably have noticed the network tab on the web panel. If you open this tab you can see the following:

What this page basically shows is all the ports that are open for you server. In this case a minecraft server is hosted and only port 25567 is opened. This means you connect to the server using the ip and behing it the port like 123.456.789:25567

You might also see more ports that are open, in this example a satisfactory is hosted, a satisfactory server requires more ports to be opened.

Additionally you can add notes to each port to remember what this port is for, and you can choose which port to make primary.

In general this is a feature you will not often use and is mostly dependent on the game server you are hosting, some servers require more ports to be opened.

If you need a specific port to be opened you will need to contact echonode support and properly explain why it needs to be opened.