I was reading about capturing packets during skype sessions to get the other person's IP address... sounds like you can do this mainly while in a live skype chat / call between skype to skype, but Is it possible to get the other person's IP by just ringing their Skype number even if they don't pick up your call? (By skype number I mean the online number you can purchase from skype, not the skype ID.) And do you basically just need internet and a capturing software for that?
Skype is a modified P2P network. You have no guarantee that your traffic is going to them, so a sniffer wouldn't work the way you'd expect. However, you can resolve the person's username to their ip address with a tool like this while they are online. So if you can get their username from the Skype number, or the email address associated with the number (to then get the skype username), you'd be able to resolve it to an ip address.