This task does not concern the regular geocoding. Regular geocoding can detect geographical coordinates (lat/lon) using postal address and vice versa.
In your case you need to detect geographical coordinates by IP address. It is so called geolocation. RadMap doesn't provide this functionality. There are several services in the Internet which could help you. For example:
But most of them aren't free. In anyway, you have to create code which will communicate with these services by yourself.
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