resolving names and ip addresses
I hope this is the right place to ask this. I have a project I need to code up and just want to sort some basic ground rules first.
I have various clients connecting to a port on a server. These clients have dynamic ip addresses so obviously they wil change each time they connect to the net.
Each client has a dns-name set up at a service such as www.no-ip.com and keeps thier actual ip updated against thier dns-name.
When a client connects to my port, I can see thier IP address.
I also have a list of all the allowed dns-names.
What I need to be able to do is either
a: resolve the connecting clients ip into thier dns name so I can compare with with my list of allowed dns-names
b: resolve each allowed dns-name into it's current ip every x minutes so I can compare the connecting ip address against the locally stored list of allowed ones.
Will either of these work (option a would be best if possible as there would be no x minute delay while my application updates it's stored ip data, but I could live with option b)
Could one of you outline roughly how I would acheive this?