What are ports 2120, 2121, and 2123 used for?

What are you doing? Is it useful? Can I use a firewall to close these 3 ports?

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What are you doing? Is it useful? Can I use a firewall to close these 3 ports?

The services I know of are not these ports by default~ They should be user-defined ports
If you want to see the default ones, you can look at the /etc/services file, which includes the default ports of most services.