[PacPers]

As mentioned, the easiest way is to use a short url that logs visits and see ip on there. The best one I've seen is www.bit.do really fast and easy to use.

Then you need the person to click on the link you provide.

The one other way I can think of is if they have an email address on their profile, you can send them an email and use an email tracking service that uses an image in the email to see the ip of the person that opened it.