How to sniff the IP address of a vistitor to the web site?

Hello Forum!

I apologize if this has already been asked and answered here.

How do I code my web site so that I can sniff out the IP address of the person visiting the site? I want to then redirect the user according to their IP address. Specifically, if the user is coming from an Arabic or Farsi country state, I want to redirect them to a different page (then if they specifically request to see the content in English, I will remember this by a cookie).

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