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Send data between processes via QSharedMemory

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  • VRoninV Offline
    VRoninV Offline
    VRonin
    wrote on last edited by
    #8

    Probably off topic, but did you consider using QLocalSocket and WINAPI Named Pipe instead

    "La mort n'est rien, mais vivre vaincu et sans gloire, c'est mourir tous les jours"
    ~Napoleon Bonaparte

    On a crusade to banish setIndexWidget() from the holy land of Qt

    MR.SmithM 1 Reply Last reply
    2
    • VRoninV VRonin

      Probably off topic, but did you consider using QLocalSocket and WINAPI Named Pipe instead

      MR.SmithM Offline
      MR.SmithM Offline
      MR.Smith
      wrote on last edited by
      #9

      @VRonin Good idea. It's will be my fallback. I need to high speed data transfer (up to 10 MBit/s) and shared memory is a faster method of IPC. It's most suitable for my application.

      1 Reply Last reply
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      • VRoninV Offline
        VRoninV Offline
        VRonin
        wrote on last edited by VRonin
        #10

        Disclaimer

        what follows is just speculation, not advice.


        The problem with shared memory, as I understand it, is that is no way to signal the reader application that new data is available to consume.

        10 MBit/s is not a lot, named pipe should be able to manage it without a problem, in fact, a TCP socket connected to localhost should also be able to handle that transfer rate without a sweat. Both their typical transfer rates are in the multiple Gbit/sec

        "La mort n'est rien, mais vivre vaincu et sans gloire, c'est mourir tous les jours"
        ~Napoleon Bonaparte

        On a crusade to banish setIndexWidget() from the holy land of Qt

        MR.SmithM 1 Reply Last reply
        2
        • SGaistS Offline
          SGaistS Offline
          SGaist
          Lifetime Qt Champion
          wrote on last edited by
          #11

          Check the detailed documentation of QSharedMemory and the setNativeKey. They explain how to achieve communication with non Qt application.

          Interested in AI ? www.idiap.ch
          Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

          1 Reply Last reply
          3
          • SGaistS SGaist

            What exact error are you getting ?

            MR.SmithM Offline
            MR.SmithM Offline
            MR.Smith
            wrote on last edited by
            #12

            @SGaist When I run two copies of Ot application and write some data to shared memory from one of them and the next trying read data from another I have problem: sharedMemory.isAttached() == FALSE for shared memory with same keys.

            jsulmJ 1 Reply Last reply
            0
            • MR.SmithM MR.Smith

              @SGaist When I run two copies of Ot application and write some data to shared memory from one of them and the next trying read data from another I have problem: sharedMemory.isAttached() == FALSE for shared memory with same keys.

              jsulmJ Offline
              jsulmJ Offline
              jsulm
              Lifetime Qt Champion
              wrote on last edited by
              #13

              @MR.Smith Didn't you say before that it is working when using two Qt apps and doesn't work if one app is not a Qt app?

              https://forum.qt.io/topic/113070/qt-code-of-conduct

              MR.SmithM 1 Reply Last reply
              0
              • VRoninV VRonin

                Disclaimer

                what follows is just speculation, not advice.


                The problem with shared memory, as I understand it, is that is no way to signal the reader application that new data is available to consume.

                10 MBit/s is not a lot, named pipe should be able to manage it without a problem, in fact, a TCP socket connected to localhost should also be able to handle that transfer rate without a sweat. Both their typical transfer rates are in the multiple Gbit/sec

                MR.SmithM Offline
                MR.SmithM Offline
                MR.Smith
                wrote on last edited by
                #14

                @VRonin Thank you for recommendation. I will try to use named pipe in my application. It's also good solution for my application.

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                • jsulmJ jsulm

                  @MR.Smith Didn't you say before that it is working when using two Qt apps and doesn't work if one app is not a Qt app?

                  MR.SmithM Offline
                  MR.SmithM Offline
                  MR.Smith
                  wrote on last edited by
                  #15

                  @jsulm Yes, it's true. I can transfer data from one Qt application to another copy of this Qt application, but I can't transfer data from Qt application to WinAPI application.

                  jsulmJ 1 Reply Last reply
                  0
                  • MR.SmithM MR.Smith

                    @jsulm Yes, it's true. I can transfer data from one Qt application to another copy of this Qt application, but I can't transfer data from Qt application to WinAPI application.

                    jsulmJ Offline
                    jsulmJ Offline
                    jsulm
                    Lifetime Qt Champion
                    wrote on last edited by
                    #16

                    @MR.Smith @SGaist pointed out what you should try

                    https://forum.qt.io/topic/113070/qt-code-of-conduct

                    1 Reply Last reply
                    1
                    • MR.SmithM Offline
                      MR.SmithM Offline
                      MR.Smith
                      wrote on last edited by
                      #17

                      I got successfully transfer data via named pipes. It's good solution and I will use it, not shared memory.
                      Thank you every one for your help and recommendations.

                      1 Reply Last reply
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