I can see your local web servers

Funny enough, the site is reporting port 3000 to be running a web server. It is not - according do nmap and my knowledge.

Any ideas on this?

If you're on Linux, BSD and macOS, you can run:

    sudo lsof -i | grep 3000

To try and see if a process has claimed the port.

On Windows:

    netstat -ab

I've forgotten so much Windows I don't know how to filter the result, but it'll give you a list of ports and processes.

If like me you saw the bright red text "If you see any results like localhost:3000 is available!" as meaning :3000 was actually available, it's just an example. The yellow box above seems to be where the results would actually be.

Some BSD systems won't have lsof out of the box, in which case fstat/netstat will give you the results you want.

I must admit, it was exactly this. I read the text without using my brain properly.

Please accept my sincere apologies.

I did exactly the same thing and spent too long running various things to find out what on Earth was using the port! Only reason I had a good guess at what it may have been.