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OT: Unique identification of a visitors pc

by Nik (Initiate)
on Dec 08, 2004 at 06:59 UTC ( #413169=perlquestion: print w/replies, xml ) Need Help??

Nik has asked for the wisdom of the Perl Monks concerning the following question:

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  • Comment on OT: Unique identification of a visitors pc

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Re: OT: Unique identification of a visitors pc
by davorg (Chancellor) on Dec 08, 2004 at 07:34 UTC

    The IP address does not uniquely identify a PC. For one thing, it's possible that the same PC will have a different IP address the next time it visits your site (if the ISP allocates addresses dynamically). And for another several PCs can appear to have the same IP simultaneously (if they are coming thru a proxy).

    --
    <http://www.dave.org.uk>

    "The first rule of Perl club is you do not talk about Perl club."
    -- Chip Salzenberg

Re: OT: Unique identification of a visitors pc
by gellyfish (Monsignor) on Dec 08, 2004 at 07:06 UTC

    The only information that you can get reliably is that which is sent in the HTTP request headers and that includes the requesting IP and any cookies that are to be sent to your domain. If you need anything more than that I would suggest that you rethink what you are trying to do as it is impossible to do reliably.

    /J\

Re: OT: Unique identification of a visitors pc
by pingo (Hermit) on Dec 08, 2004 at 07:06 UTC
    Don't know if it is possible to do that. You could always get $ENV{HTTP_USER_AGENT}, but that is hardly unique.

    Of course, if you are doing something like trying to prevent visitors from voting in a poll more than once, you could always use cookies, but that is easy to get around anyway.
Re: OT: Unique identification of a visitors pc
by Zed_Lopez (Chaplain) on Dec 08, 2004 at 13:27 UTC

    Here's a good rundown of why the enterprise is doomed.

    Your best bet would be to set a cookie. But I know that, as a user, I find gratuitous cookies annoying, and block them.

      Agreed ZL. I see an ethics problem here. Visitors to a site do not want their privacy invaded without permission. It is morally wrong to try to do this.
Re: OT: Unique identification of a visitors pc
by Jaap (Curate) on Dec 08, 2004 at 07:42 UTC
    If you can run something on the pc, you could use that PC's MAC address. If not, i don't see how.
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Re: OT: Unique identification of a visitors pc
by PreferredUserName (Pilgrim) on Dec 08, 2004 at 11:36 UTC
    Why don't you want to just set a unique cookie?
Re: OT: Unique identification of a visitors pc
by inman (Curate) on Dec 09, 2004 at 04:05 UTC
    As an alternative to session handling using cookies, try URL re-writing. This doesn't depend on a users cookie settings or IP address. This technique is often used when cookie based session management has been tried already.
      The OP isn't asking for session handling, he's asking for persistent client identification, which URL re-writing is not going to address.
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Re: OT: Unique identification of a visitors pc
by Anonymous Monk on Dec 09, 2004 at 03:06 UTC
    Try searching, this question is asked often.

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