Getting started with the MQTT client for C

Compile and run the MQTT client sample C app from the command line. The sample is in the MQTT SDK. It demonstrates an MQTT publisher and subscriber.

@echo off
setlocal
call "C:\Program Files\Microsoft Visual Studio 10.0\VC\vcvarsall.bat" x86
cl  /nologo /D "WIN32" /I "..\include" "MQTTV3Sample.c" /link /nologo ..\windows_ia32\mqttv3c.lib
set path=%path%;..\windows_ia32;
start "MQTT Subscriber" MQTTV3Sample -a subscribe -b localhost -p 1883
@rem Sleep for 2 seconds
ping -n 2 127.0.0.1 > NUL 2>&1
MQTTV3Sample -b localhost -p 1883
pause
endlocal

Results

The publisher and subscriber write output to their command windows:

Compile and run the MQTT client sample C app from the Microsoft Visual Studio. The sample is in the Mobile Messaging and M2M Client Pack. It demonstrates an MQTT publisher and subscriber.

1. Start Microsoft Visual Studio.
2. Create a new project from existing code.
   1. Click File > New > Project from Existing Code.
   2. Select Visual C++ as the type of project to create.
   3. Click Next.
3. Specify the parameters in the Project Location and Source Files window.
   1. Click Browse and locate the sdkroot\SDK\clients\c\samples directory.
   2. Name the project MQTTV3Sample.
   3. Click Next.
4. Select Console application project in the Project type list. Click Finish
5. Configure only the Debug configuration.

   By default Microsoft Visual Studio creates both a release and debug configuration. In the tutorial, you configure the debug configuration. To suppress build errors, clear the Build option for the release configuration.

   1. Click Project > MQTTV3Sample Properties > Configuration Manager. Select Release as the Active solution configuration and clear Build.
   2. Select Debug as the Active solution configuration > Close.

      Check that you are modifying the Debug configuration in all the following steps.

6. Modify the C/C++ settings in the MQTTV3Sample Property Pages.
   1. In the MQTTV3Sample Property Pages window, open Configuration properties > C/C++ > General.
   2. In the list of general properties, click Additional Include Directories, and add your directory path to sdkroot\SDK\clients\c\include and click Apply.
7. Modify the Linker settings
   1. Open Configuration properties > Linker > General.
   2. In the list of general properties, click Additional Library Directories, and add your directory path to sdkroot\SDK\clients\c\windows_ia32
   3. In the list of Linker properties, click Command line. Type mqttv3c.lib in the Additional options data entry area and click Apply.
8. Remove the MQTTV3SSample.c source file from the project.
   1. Open the MQTTV3sample > Source Files folder in the Solution Explorer window.
   2. Right-click MQTTV3SSample.c > Exclude from Project
9. Build the MQTTV3Sample project.
   1. Right-click the MQTTV3sample project in the Solution Explorer and click Build.

      The build completes without any errors.

10. Add two new projects to run MQTTV3Sample as both a Subscriber and Publisher runtime instance.

    The Publisher and Subscriber projects are to contain the commands to run the MQTTV3Sample. They are not built, and contain no code.

    1. In the Solution Explorer, right-click Solution `MQTTV3Sample` > Add > New project.
    2. Type Subscriber into the Name field. Leave Win32 Console Application selected. Click OK.

       The Win32 Application Wizard starts.

    3. In the Win32 Application Wizard, click Next. Check Empty project > Finish
    4. Repeat these steps to add a Publisher project.
    5. Right-click the Subscriber project and click Set as StartUp project
    The Solution Explorer window is shown in Figure 3.

    

11. Configure the Subscriber property pages.
    1. Right-click Subscriber in the Solution Explorer Properties > Configuration Properties > Properties > Debugging

       Check the window title is Subscriber Property Pages.

    2. Click Environment. Type path=%path%;sdkroot\SDK\clients\c\windows_ia32 and click Apply.

       Change sdkroot to suit your environment.

    3. Click Command, and replace $(TargetPath) by the path to the MQTTV3Sample module

       For example, sdkroot\SDK\clients\c\samples\debug\MQTTV3Sample

       Change sdkroot to suit your environment.

    4. Click Command Arguments and type -a subscribe -b localhost -p 1883 and click Apply.
12. Configure the Publisher property pages.
    Tip: You can switch the property pages project by clicking the projects in the Solution Explorer window.
    1. Repeat the Subscriber steps for the Publisher.

       The command argument is -b localhost -p 1883

13. Stop the build process that builds the Publisher and Subscriber projects.
    1. In the property pages of any of the projects, click Configuration Manager and clear Build for the Publisher and Subscriber in both the Release and Debug configurations. Click Close.
14. Run the sample.
    1. Click F5 to start the Subscriber
    2. Right click Publisher in the Solution Explorer, Debug > Start a new instance

Results

The publisher and subscriber output to command windows. Visual Studio closes the publisher window. Look at the subscriber window, which is shown in the following figure, then close the subscriber window.