Send data between processes via QSharedMemory

[SGaist]

Hi and welcome to devnet,

Did you see that you are not using the same key for both applications ?

For the Qt application you are using backslashes and for the WinAPI application your are using forward slashes.

[MR.Smith]

@SGaist Thank you! I'm fix it. But it's doesn't fix a problem. I'm already testing both variants. In my post it is only typo.

[SGaist]

I don't remember if there's a limitation in the characters you can use as key, but i'd start with only ASCII stuff without any special signs.

[MR.Smith]

I'm already try to run two copies of Qt application. And it can't transfet data from one thread to another.

[SGaist]

What exact error are you getting ?

[MR.Smith]

@SGaist I'm changed value of key to simple ASCII: "example".
Not effect (((
May be you have an example? I searching it in Google but only one example in qt.io was found.
No any other(((

[VRonin]

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

[MR.Smith]

@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.

[VRonin]

Disclaimer

what follows is just speculation, not advice.

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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

[SGaist]

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

[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.

[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.Smith]

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

[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.

[jsulm]

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

[MR.Smith]

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.