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Thread: Mobile IP

  1. #1
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    Jul 2003
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    Mobile IP

    Mobile IP
    Dear All,

    Is there any way to know the IP address of a handy when it connects to the GPRS network ( for example when it accesses to a server ) ?

    Thanks a lot,
    Brgds/Linh

    P.S: This msg was also in the forum J2ME general before. sorry for the repeated post.

  2. #2
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    If you connect to a server, that server can simply reply with the IP that it received the connection from. But in all likelihood that will not be the IP of the phone but the IP of the NAT gateway or firewall that the phone is behind. The phone's IP on that internal, non-routable network cannot be obtained through J2ME.
    --G

  3. #3
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    Jul 2003
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    Hi ggould,

    I agree with you that the server responds to the IP address of the NAT/proxy server at which the mobile device is behind.
    I assume traffic data then will be routed to the mobile device via data tunnels of GPRS network.

    Do you know whether or not, in principle, a network operater can assign for the mobile device a fixed IP address ( of course at NAT/proxy server ) . And how about the possibility that this IP address is visible to external networks ?

    Thanks a lot for your answer.
    Brgds,Linh.

  4. #4
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    T-Mobile and AT&T Wireless both put their phones behind a simple Cone NAT, so if you use C++ rather than Java you can use NAT detection and deflation tools like STUN. But current MIDP implementations do not provide the necessary interfaces -- no UDP (except from Sprint), no ability to check your own IP address at all.

    While there is no reason in theory that a carrier couldn't hand out static, routable IPs rather than using a NAT, in practice you are extremely unlikely to find any carrier that will do that. Phone companies are downright reptilian in their desire to keep control over their networks, and they don't control routable IP space. Their excuse is generally that the shortage of IPv4 addresses makes NATting necessary, though of course they are doing next to nothing to migrate to IPv6.

    So, don't get your hopes up. NAT -- and the absence of real IP addresses -- is what we developers have to live with. We'll be rolling our own routing until the last carrier is strangled with the entrails of the last handset manufacturer.
    --G

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