error: Unknown module(s) in QT: mqtt

[Jo Jo]

I'm trying to use the mqtt module, but when I write QT += mqtt in the .pro file, I get the error: error: Unknown module(s) in QT: mqtt.

I searched for the mqtt module in the Maintenance Tool, but it's not listed. Isn't mqtt a standard module included with Qt? What's the problem?

I'm using Qt 6.10.1 with C++. Compiling on Windows using qmake/msvc

[Jo Jo]

Here is solution:

1. create mqtt directory
2. run "git clone git://code.qt.io/qt/qtmqtt.git -b 6.10.1" in this directory
3. open qtmqtt directory and create build folder in it
4. open "X64 native tools command prompt for VS 2022" in build folder and run following commands:

To build Release version:
cmake -S .. -B build -G "Ninja" -DCMAKE_CONFIGURATION_TYPES="Release" -DCMAKE_PREFIX_PATH="C:\Qt\6.10.1\msvc2022_64" -DCMAKE_INSTALL_PREFIX="C:\Qt\6.10.1\msvc2022_64" -DCMAKE_MAKE_PROGRAM="C:\Program Files\Microsoft Visual Studio\2022\Community\Common7\IDE\CommonExtensions\Microsoft\CMake\Ninja\ninja.exe"
cmake --build build --config Release
cmake --install build

To build Debug version:
cmake -S .. -B build -G "Ninja Multi-Config" -DCMAKE_CONFIGURATION_TYPES="Debug;Release" -DCMAKE_PREFIX_PATH="C:\Qt\6.10.1\msvc2022_64" -DCMAKE_INSTALL_PREFIX="C:\Qt\6.10.1\msvc2022_64" -DCMAKE_MAKE_PROGRAM="C:\Program Files\Microsoft Visual Studio\2022\Community\Common7\IDE\CommonExtensions\Microsoft\CMake\Ninja\ninja.exe"
cmake --build build --config Debug
cmake --install build --config Debug

[jsulm]

@Jo-Jo I'm not sure, but I think mqtt is only available as binary for commercial users. You can still build it from source though.

[Jo Jo]

@jsulm It also available under GPL https://doc.qt.io/qt-6/qtmqtt-index.html

I compiled the project using the following commands:
git clone git://code.qt.io/qt/qtmqtt.git -b 6.10.1
and then from build directory:
cmake -S .. -B build -G "NMake Makefiles" -DCMAKE_BUILD_TYPE=Release -DCMAKE_PREFIX_PATH="C:\Qt\6.10.1\msvc2022_64" -DCMAKE_INSTALL_PREFIX="C:\Qt\6.10.1\msvc2022_64"
cmake --build build --config Release
cmake --install build

But this builds the mqtt module for release. I tried building it for debug, but it still only builds for release. How do I build it for debug version?

[jsulm]

@Jo-Jo said in error: Unknown module(s) in QT: mqtt:

I tried building it for debug

In a fresh build folder?

[Jo Jo]

@jsulm Yes, In a fresh build folder

[jsulm]

@Jo-Jo How exactly do you build for debug?

[Jo Jo]

@jsulm said in error: Unknown module(s) in QT: mqtt:

@Jo-Jo How exactly do you build for debug?

cmake -S .. -B build -G "NMake Makefiles" -DCMAKE_BUILD_TYPE=Debug -DCMAKE_PREFIX_PATH="C:\Qt\6.10.1\msvc2022_64" -DCMAKE_INSTALL_PREFIX="C:\Qt\6.10.1\msvc2022_64"
cmake --build build --config Debug
cmake --install build

and after cmake -S .. -B build -G "NMake Makefiles" -DCMAKE_BUILD_TYPE=Debug -DCMAKE_PREFIX_PATH="C:\Qt\6.10.1\msvc2022_64" -DCMAKE_INSTALL_PREFIX="C:\Qt\6.10.1\msvc2022_64"

I see following output:
...
-- Setting build type to 'Release' as none was specified.

It does not recognize debug mode

[JoeCFD]

@Jo-Jo I guess you built only Qt module for using mqtt.
Mqtt needs to be installed separately. Check the following out:
https://mosquitto.org/download/

[SGaist]

@Jo-Jo Hi,

If you have ccmake you can check visually what is configured to find out what is happening.

@JoeCFD said in error: Unknown module(s) in QT: mqtt:

@Jo-Jo I guess you built only Qt module for using mqtt.
Mqtt needs to be installed separately. Check the following out:
https://mosquitto.org/download/

It's unrelated to the problem at hand. @Jo-Jo wants to use/build the QtMQTT module.

[Jo Jo]

Here is solution:

1. create mqtt directory
2. run "git clone git://code.qt.io/qt/qtmqtt.git -b 6.10.1" in this directory
3. open qtmqtt directory and create build folder in it
4. open "X64 native tools command prompt for VS 2022" in build folder and run following commands:

To build Release version:
cmake -S .. -B build -G "Ninja" -DCMAKE_CONFIGURATION_TYPES="Release" -DCMAKE_PREFIX_PATH="C:\Qt\6.10.1\msvc2022_64" -DCMAKE_INSTALL_PREFIX="C:\Qt\6.10.1\msvc2022_64" -DCMAKE_MAKE_PROGRAM="C:\Program Files\Microsoft Visual Studio\2022\Community\Common7\IDE\CommonExtensions\Microsoft\CMake\Ninja\ninja.exe"
cmake --build build --config Release
cmake --install build

To build Debug version:
cmake -S .. -B build -G "Ninja Multi-Config" -DCMAKE_CONFIGURATION_TYPES="Debug;Release" -DCMAKE_PREFIX_PATH="C:\Qt\6.10.1\msvc2022_64" -DCMAKE_INSTALL_PREFIX="C:\Qt\6.10.1\msvc2022_64" -DCMAKE_MAKE_PROGRAM="C:\Program Files\Microsoft Visual Studio\2022\Community\Common7\IDE\CommonExtensions\Microsoft\CMake\Ninja\ninja.exe"
cmake --build build --config Debug
cmake --install build --config Debug