Hi again.
and I have some examples from my own personal experience. So I don't believe that you can say there is a "best" method, for all situations.
Yes I can. Host information can be spoofed. So can IP Addresses. Here is the point you are missing, if he is going to connect to your system then he is going to do it via IP address not using his FQDN and the network could care less about FQDN. Packets are not routed using FQDN they are routed via IP Address and Mac's. So while FQDN is an option it is not as reliable as the IP Address. So what are you going to do now a reverse lookup? How often do they match what you are looking for these days? Not often.
You can always create a packet that says you are this or that but without the true IP address you'll never get a response which means you will never get connected.
I agree on that and it's the reason why I finally decided not to use fqdns.
Thank you both for the detailed explanation :)
Best Regards Marcus