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Re: Controlling the Number of Simultaneous Users

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  • guillemvic
    ... Remember that UDP is unreliable if you need all of the other instances to answer, since it is a send-and-forget protocol. No control is done at UDP
    Message 1 of 15 , Dec 1, 2007
      --- In firebird-support@yahoogroups.com, "Dan Cooperstock" <dcoops@...>
      wrote:
      >
      >
      > That idea is fairly similar to the idea someone on an ASP
      > (Association of Shareware Professionals) forum suggested, which is to
      > send out a multicast UDP packet on startup, that other instances of
      > my program on the same subnet respond to with "Yes, I'm here". The
      > sender counts the responses, and if they exceed the licensed # of
      > users (minus one, to allow the sender to run), prevents the sender
      > from running.
      >
      > This actually seems a bit simpler, because it doesn't need a server
      > program, and isn't affected by crashes.
      >
      > Any comments on that idea? Thanks.
      >

      Remember that UDP is unreliable if you need all of the other instances
      to answer, since it is a send-and-forget protocol. No control is done
      at UDP protocol level to assure all instances have answered.

      That is no big problem if you know who should be online, but it would
      be in your case IMHO. Personally I would go for a solution like Lee
      proposes.

      Regards,

      Guillem
    • Lee
      A scheme like this is easily circumvented with a firewall. Maybe I m a little paranoid, but my firewall is set such that permission for any kind of network
      Message 2 of 15 , Dec 1, 2007
        A scheme like this is easily circumvented with a firewall.

        Maybe I'm a little paranoid, but my firewall is set such that
        permission for any kind of network access is asked for any new app.
        Apps that have no valid reason to access the network get a permanent
        block.

        Another Lee


        > That idea is fairly similar to the idea someone on an ASP
        > (Association of Shareware Professionals) forum suggested, which is to
        > send out a multicast UDP packet on startup, that other instances of
        > my program on the same subnet respond to with "Yes, I'm here". The
        > sender counts the responses, and if they exceed the licensed # of
        > users (minus one, to allow the sender to run), prevents the sender
        > from running.
        >
        > This actually seems a bit simpler, because it doesn't need a server
        > program, and isn't affected by crashes.
        >
        > Any comments on that idea? Thanks.
        >
      • Alexandre Benson Smith
        ... I problem I see here is when uses Terminal Services, all connections came from the same IP address see you ! -- Alexandre Benson Smith Development THOR
        Message 3 of 15 , Dec 1, 2007
          Lee Jenkins wrote:
          > The license manager also tracks the IP of the workstation that gets clearance to
          > run so that if the workstation or license manager were to go down for some
          > reason, the license manager would read the IP of the incoming request when
          > restarted and determine that the workstation was already allowed to run

          I problem I see here is when uses Terminal Services, all connections
          came from the same IP address

          see you !

          --
          Alexandre Benson Smith
          Development
          THOR Software e Comercial Ltda
          Santo Andre - Sao Paulo - Brazil
          www.thorsoftware.com.br
        • tomkrej
          ... Hello, but what s about Firewalls?? We used this kind of controll, but we left it, because some users close the lines by firewalls, it s not a problem if
          Message 4 of 15 , Dec 3, 2007
            --- In firebird-support@yahoogroups.com, "Woody" <woody-tmw@...> wrote:
            >
            > From: "Dan Cooperstock" <dcoops@...>
            > >
            > > That idea is fairly similar to the idea someone on an ASP
            > > (Association of Shareware Professionals) forum suggested, which is to
            > > send out a multicast UDP packet on startup, that other instances of
            > > my program on the same subnet respond to with "Yes, I'm here". The
            > > sender counts the responses, and if they exceed the licensed # of
            > > users (minus one, to allow the sender to run), prevents the sender
            > > from running.
            > >
            > > This actually seems a bit simpler, because it doesn't need a server
            > > program, and isn't affected by crashes.
            > >
            > > Any comments on that idea? Thanks.
            >

            Hello,
            but what's about Firewalls??
            We used this kind of controll, but we left it, because some users
            close the lines by firewalls, it's not a problem if You have a little
            bit better firewall than that i WinXP.

            We rather use our own firebird user, we block SYSDBA by role named
            SYSDBA, a we count how many users are connected to database. It's
            effective and the only problem starts, when some client PC fails and
            the server keep connection for some 5, 10 or 15 minutes.
            But this is not a serious problem.

            Tom
          • Jarrod Hollingworth
            Hi Guillem, ... It is very reliable in local area networks which is what we re talking about in this license checking. At least one commercial software
            Message 5 of 15 , Dec 5, 2007
              Hi Guillem,

              > Remember that UDP is unreliable if you need all of the other instances
              > to answer, since it is a send-and-forget protocol. No control is done
              > at UDP protocol level to assure all instances have answered.

              It is very reliable in local area networks which is what we're talking about
              in this license checking. At least one commercial software protection system
              implements a similar license checking technique using the mailslot protocol
              instead of UDP. It's very similar in nature but gets through almost all
              personal firewall software (such as ZoneAlarm, Norton Internet Security,
              McAffee...) except for the Windows XP firewall (incoming side).

              With any broadcast where all listeners respond it would be a good idea to
              implement a random delay (say 0 to 1000ms) before responding. This increases
              the reliability and need to retransmit.

              We're getting off-topic though so I'll stop here.

              Regards,
              Jarrod Hollingworth

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            • Jarrod Hollingworth
              Hi Tom, ... The problem with this approach is that things like backups and other DB utilities (such as a batch reporting system, separate view only tool that
              Message 6 of 15 , Dec 5, 2007
                Hi Tom,

                > We rather use our own firebird user, we block SYSDBA by role named
                > SYSDBA, a we count how many users are connected to database. It's
                > effective and the only problem starts, when some client PC fails and
                > the server keep connection for some 5, 10 or 15 minutes.
                > But this is not a serious problem.

                The problem with this approach is that things like backups and other DB
                utilities (such as a batch reporting system, separate "view only" tool that
                you provide, server info/maintenance tool) also use connections which may
                give a false impression of the number of active users.

                Regards,
                Jarrod Hollingworth

                * Are your projects profitable?
                * Are you billing your customers accurately?
                * Where do you or your staff spend their time?
                Complete Time Tracking ###
                EASY, ACCURATE and FLEXIBLE time tracking ###
                for single or multiple users. ###
                http://www.complete-time-tracking.com ###
                * Try it free, fully functional for 30 days.
              • tomkrej
                ... tool that ... which may ... Hello, it s not a problem, we have two additional users: one for view only tools - that have granted select only for necessary
                Message 7 of 15 , Dec 6, 2007
                  > The problem with this approach is that things like backups and other DB
                  > utilities (such as a batch reporting system, separate "view only"
                  tool that
                  > you provide, server info/maintenance tool) also use connections
                  which may
                  > give a false impression of the number of active users.
                  >

                  Hello, it's not a problem, we have two additional users:
                  one for view only tools - that have granted select only for necessary
                  tables, and insert for two tables (log, requests for reservation)
                  second for backups - select for all tables, no inserts, no updates

                  And we count only our Editable users - so no problem.

                  Tom
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