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feedback requested on idea: method of restricting LAN use of app

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  • feedback requested on idea: method of restricting LAN use of app

    I just had an idea, Id like some critical feedback on it... basically, i want my program to have two license options - single user, and multi-user... if its a single-user license, then only one computer in the LAN should be able to run my program.
    Here is my idea on one way of possibly enforcing a single-user license so that only one computer in the LAN can have my program installed...

    All Windows machines as far as I know have two 'public network fields' - a computername, and a description.
    When my app launches (single-user license), it should make sure that the last character in its local description field is set to chr$(160), which is a visually space character, but not the real space character. Then, it should get a list of machines in the LAN (im sure theres already code posted to do that), and then grab the description field for each one also. If any of the computers have chr$(160) at the end of their description, then your program can tell that another copy of your program is installed on another computer. Obviously your uninstall program should remove the 160 character from the end.
    Any thoughts on this? I wouldnt want to ever modify the computername field, but appending chr$(160) to the description field seems harmless enough.. ?


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  • #2
    Wayne,

    what if the WINS server isn't running or they disable NetBios Names?

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    -Greg
    -Greg
    [email protected]
    MCP,MCSA,MCSE,MCSD

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    • #3
      What if my killer application has the same "harmless" license restriction idea of changing "computername" by appending a character?

      I guess then it depends on whose application loads first, huh?

      Why not just open some file on the server for exclusive use if single user, shared use if multi-user?

      Better yet, you should enforce restrictions the old-fashioned way: by offering quality products with good service at a fair price. Then all your customers will be happy to honor license restrictions.

      Note: I only sell business-to-business; this may not work for consumer software.

      MCM


      Michael Mattias
      Tal Systems (retired)
      Port Washington WI USA
      [email protected]
      http://www.talsystems.com

      Comment


      • #4
        Wayne,

        an easy way is a broadcast to your subnet.
        Will only work if IP is bound to your network card.

        The MS way are DCOM DLL's. They can replicate all over the net
        "infecting" every reachable PC and will work with any
        protocol ( netBui, IPX, IP ).

        Hard to say which one is better. You should use broadcast for
        a "mixed" net and force the user during install to bind the
        IP prot. to his netcard.

        As i remember there's a DCOM sample at the March/01 MSDN CD.

        Ralph


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        • #5
          Wayne,

          Limiting programs to single users is easy. Simply create
          a small file and have your program open it in exclusive mode.

          The next user cannot run your program until the previous user
          closes the file (ends the program).

          HTH,
          --Bob

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          "It was too lonely at the top".

          Comment


          • #6
            I agree in most part with the comments....Most
            companies are honest and buy the required copies. As far
            as what your tring to do there's lots of ways, just depends
            on how deep you want to go into the layers of the LAN.
            You may want to look up DLC on msdn and that will get you
            down to the layer just above the hardware driver. i.e. bypasses
            netbuie, netbios, TCP/IP ect. Since each LAN card has a unique
            address it doesn't matter what the computer name is you'll
            know what pc is making the request. There's not much info on the
            API but its there. Kinda like they say you can't access I/O ports
            in win NT / 2000 without a driver...Not true but not easy to
            figure out ether. Its in msdn DDK

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            • #7
              Thanks all, it was just an idea that sprung into my head out of nowhere - I wasnt even thinking anything related at the time, so I dont mind copping a bit of abuse for it

              Bob,
              Limiting programs to single users is easy. Simply create
              a small file and have your program open it in exclusive mode.
              That's a simple and convenient idea - my question, if you did implement that, how would you find the server, and then how would you find somewhere on it with write access?




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              • #8
                Wayne;

                Just to weight in with my 2 cents..

                Unfortuneately, the world's current computer environment
                includes "script kiddies" creating virii, trojan horses, and
                zombie programs. Steve Gibson's site weathered a ddos, and
                his story about it is a good read -- http://grc.com.

                Given that, I've become more paranoid in my old age, and when
                I set up new computers on my network, I do everything I can to
                keep them from talking with one another.




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                [email protected]
                http://www.northnet.org/bdurland
                Real programmers use a magnetized needle and a steady hand

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