When there genuinely is no web server installed on a machine, and the user types in the machine’s IP address or FQDN into the web browser, the user will get a genuine “can’t connect to the server” message from the web browser.
However, after installing the Apache web server, the direct IP address and the FQDN (i.e. archimedes.example.com) will now show the default “It works!” page. How can I make my server act as if there is no server in these places (for the IP and the FQDN)?
Note that a 404 error does not qualify, because that makes it clear that a web server is available.
Is this even possible to do in the first place?
The goal of this is that I just want my regular websites, say genuinewebsite.com, that is genuinely supposed to be on this server to be recognized. All the other “default” addresses (the IP address and FQDN) that really have no connection to any websites should just act as if there is no web server there in the first place.
No, it is not possible, because to get the hostname the browser used for the request, the browser first has to connect successfully and send it in the request. By that time, you can’t really refuse the connection; the best you can do is close it on them which will appear as a connection reset error.