You can not actually find out the street address of a user by their IP address. You can get the general location (within a particular city). Possibly, law enforcement, with a search warrant, could get the address of the user by requesting the information from a company that issued the IP Address to the user. Many IP addresses are issued dynamically and change, so unless the company issuing the IP is keeping very detailed records, they might not even know who is actually was using the IP at any given time.