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  1. #1
    Registered User
    Join Date
    Nov 2003
    London, UK

    is my phone's IP # unique?

    I've managed to get my IP number, by writing a php page and getting the REMOTE_ADDR string.


    $clientip = $_SERVER['REMOTE_ADDR'];

    echo 'phone ip:'.$clientip;


    what i would like to know is whether i could use this ip number to track this specific phone. i.e. as a login name/password. so if a user logs on to my server today and uploads some files, in a month's time, then can come back and get only the files they uploaded. or will their ip change, or is it shared by other mobile users?

  2. #2
    Registered User
    Join Date
    Jul 2003
    No, for two reasons.

    First, the IP address that you are seeing from outside of the carrier network is that of a NAT gateway. If you asked the phone for its address, by using eg Connection.getLocalAddress() you would get a different address in one of the non-routable segments of IP space (10.x most likely).

    Second, a phone gets a new "networking context" (rather like a DHCP lease) each time it connects to the network, so if the phone is idle or turned off, it will likely be given a different internal address when it is next turned on, which may well map to a different external (gateway) address.

    In summary, many phones will have the same external IP address, and a given phone will change both internal and external address if it is turned off, takes a long voice call, or is idle for more than a few minutes. IP address is useless for your purposes.

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