If port 443 is open does this definitely means taht the remote host has a certificate?

Question

I know that if port 443 is open that means the remote host supports the secure protocol https that encrypts the traffic, and therefore, the remote host has private and public key pairs.

But my question is: If I knew that port 443 for a remote host is open, does this definitely means the remote host has a certificate ? Is it possible that there is a remote host which has private/public key pairs without certificate at all ??

Answer 1

I can run whatever I want on port 443. I can run on it also http (withous 's').

So, the answer is no! It doesn't means that that host has a certificate. Not even a public/private key system.