How to find out open ports on a public IP address

I Recentely implemented Portforwarding and it is working fine.
<Public IP address>:23223 forwarded to <Internal IP>:3389. which is using for a remote desktop for a temperary period of time.

I just want to find out that port is opened or not?

I tried commands
nmap <ipaddress> - not showing that port is opened

Can anyone help me to list the ports opened on the Public IP?

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Reply to: How to find out open ports on a public IP address
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Clarification Request
My question

Is if there is nothing that responds to a UDP or TCP request, then does it matter?

Also, your router drops all unsolicited inbound connection requests (default) so is that closed too?

As to your remote desktop, you test by actually trying it.

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How to find out open ports on a public IP address

When running this command it is giving me two results. which is port 80 and port 443.

I Tested by actually trying it. I also used that command while I am using remote desktop.

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Which is why I asked the questions.

A port could be open but have no responder (AKA service or server) there and thus fail to show as open.

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MY answer

It has responder.

I am thinking, It might be the reason because I am not using a standard ports like 80, 443, 3389....etc. what you think?

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