Windows IoT Docs

MQTT Communication with Windows IoT

This tutorial walks you through setting up MQTT communication on a Windows IoT device using .NET and the M2Mqtt library.

Prerequisites

• Windows 10 IoT Core installed on a Raspberry Pi (or compatible device)
• Visual Studio 2022 with the Desktop Development with .NET workload
• Basic knowledge of C# and asynchronous programming
• An MQTT broker (you can use Mosquitto locally or a cloud broker like Google Cloud IoT)

Step 1 – Create a UWP App

Open Visual Studio, create a new Blank App (Universal Windows) project, and name it IoTMqttDemo.

Step 2 – Add the MQTT NuGet package

Install-Package M2Mqtt -Version 4.3.0

Step 3 – Write the MQTT Helper

Replace the contents of MainPage.xaml.cs with the code below. It connects to the broker, subscribes to a topic, and publishes a message every 5 seconds.

using System;
using System.Text;
using System.Threading.Tasks;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;
using uPLibrary.Networking.M2Mqtt;
using uPLibrary.Networking.M2Mqtt.Messages;

namespace IoTMqttDemo
{
    public sealed partial class MainPage : Page
    {
        private MqttClient _client;
        private const string BrokerAddress = "broker.hivemq.com";
        private const string Topic = "windows/iot/demo";

        public MainPage()
        {
            this.InitializeComponent();
            Loaded += MainPage_Loaded;
        }

        private async void MainPage_Loaded(object sender, RoutedEventArgs e)
        {
            await ConnectMqttAsync();
        }

        private Task ConnectMqttAsync()
        {
            return Task.Run(() =>
            {
                _client = new MqttClient(BrokerAddress);
                _client.MqttMsgPublishReceived += Client_MqttMsgPublishReceived;
                string clientId = Guid.NewGuid().ToString();
                _client.Connect(clientId);
                _client.Subscribe(new[] { Topic }, new[] { MqttMsgBase.QOS_LEVEL_AT_LEAST_ONCE });

                // Publish a heartbeat message
                var timer = new DispatcherTimer { Interval = TimeSpan.FromSeconds(5) };
                timer.Tick += (s, e) =>
                {
                    string payload = $"{{ \"timestamp\": \"{DateTime.UtcNow:o}\" }}";
                    _client.Publish(Topic, Encoding.UTF8.GetBytes(payload));
                };
                timer.Start();
            });
        }

        private async void Client_MqttMsgPublishReceived(object sender, MqttMsgPublishEventArgs e)
        {
            string message = Encoding.UTF8.GetString(e.Message);
            await Dispatcher.RunAsync(Windows.UI.Core.CoreDispatcherPriority.Normal, () =>
            {
                ReceivedTextBlock.Text = $"Received: {message}";
            });
        }
    }
}

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Step 4 – Update the UI

Add a simple UI to MainPage.xaml to display incoming messages.

<Page
    x:Class="IoTMqttDemo.MainPage"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="using:IoTMqttDemo"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    mc:Ignorable="d">

    <Grid Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
        <StackPanel HorizontalAlignment="Center" VerticalAlignment="Center">
            <TextBlock Text="MQTT Demo – Windows IoT" FontSize="24" FontWeight="Bold" Margin="0,0,0,20"/>
            <TextBlock x:Name="ReceivedTextBlock" Text="Waiting for data..." FontSize="16"/>
        </StackPanel>
    </Grid>
</Page>

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Step 5 – Deploy to the Device

1. Connect your Raspberry Pi to the network and enable remote debugging in the IoT Dashboard.
2. Select Remote Machine as the target and enter the device IP.
3. Press F5 to build and deploy.

Debugging Tips

• Use Device Portal to view logs (System.Diagnostics.Debug.WriteLine).
• Verify broker connectivity with a desktop MQTT client (e.g., MQTT Explorer).
• Check network firewall rules if the device cannot reach the broker.