Unable to run an example using MQTT

[nsourl]

Hi,

I am having an issue to run a simple QT WebAssembly example with Qt MQTT because I receive the below compilation error:

Project ERROR: Unknown module(s) in QT: mqtt

Qt version: 5.15.0

emscripten version: 1.39.8

Depending on Qt official documentation the MQTT module is supported but I can not verify it in my case.

https://wiki.qt.io/Qt_for_WebAssembly#Supported_Qt_Modules

Any suggestions or ideas why I am having this compilation error ?

Note: I am able to run normally other WebAssembly examples without using QT MQTT module.

Thanks.

[JKSH]

Hi @nsourl, and welcome!

You probably have to build the Qt MQTT libraries first. Download the source code from https://code.qt.io/cgit/qt/qtmqtt.git/tree/ and build it for WebAssembly.

[nsourl]

Hi @JKSH ,

Thank you for your reply!

But I have already downloaded the Qt MQTT source code during Qt 5.15.0 installation and I am running normally the MQTT app using g++ on my 64-bit desktop computer. So, this is not enough and I have to build the source code of Qt MQTT explicitly for WebAssembly?

Thanks.

[JKSH]

@nsourl said in Unable to run an example using MQTT:

I have already downloaded the Qt MQTT source code during Qt 5.15.0 installation and I am running normally the MQTT app using g++ on my 64-bit desktop computer.

OK, you have the Qt MQTT libraries built for x86_64 applications.

You also need the Qt MQTT libraries built for WebAssembly applications.

So, this is not enough and I have to build the source code of Qt MQTT explicitly for WebAssembly?

Correct. x86_64 and WebAssembly are completely different and incompatible platforms.

Think of it this way: 64-bit Windows desktop libraries can only be used with 64-bit Windows desktop applications. They cannot be used in:

• 32-bit Windows desktop applications
• 64-bit Linux applications
• 64-bit macOS applications
• WebAssembly applications
• Android applications
• iOS applications

For each platform above that you want to support, you need to download or build a dedicated set of libraries.

[nsourl]

Hi @JKSH ,

Now it's clear enough what I have to do, then I will try to build the source code for Qt WebAssembly and generate the necessary set of libraries.

I appreciate your help on this!

Thanks.