Raven Node on different port?

Hi! I'm trying to support the network with a node and I'm playing around on windows, an ubuntu machine and also on my old Pi 2's…

Port 8767 works fine, but I then realized that on https://www.ravennodes.com/nodes/ you find several nodes that are on different ports.

I'm just curious how to achieve that. Neither starting raven-qt -port 8771 nor anything else does the trick for me. You can also only let a router port forward from one port to one computer at a time (ignoring docker swarm etc).

As there are several IP's double or tripple in that list with multiple ports, how should I achieve that myself? For example making my 5 Pi 2's listen on ports 8767, 8768, 8769, 8770 and 8771 to create 5 Nodes.

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Thanks a lot guys!

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P.S.: don't plan on running 10 nodes at home but I'm just curious. or would 10 nodes help (500/500 internet here)?