Start MQTT Client with C#

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Start MQTT Client with C#

First Look to MQTT Client in C#


3 min read

we're going to have a look at What is MQTT and how can create a simple MQTT client.

But first, we need to know ...

What is MQTT?

according to

MQTT is an OASIS standard messaging protocol for the Internet of Things (IoT). It is designed as an extremely lightweight publish/subscribe messaging transport that is ideal for connecting remote devices with a small code footprint and minimal network bandwidth. MQTT today is used in a wide variety of industries, such as automotive, manufacturing, telecommunications, oil and gas, etc.

MQTT Publish / Subscribe Architecture



The broker is responsible for receiving all messages, filtering the messages, determining who is subscribed to each message, and sending the message to these subscribed clients. The broker is at the heart of any publish/subscribe protocol. Depending on the implementation, a broker can handle up to millions of concurrently connected MQTT clients.


An MQTT client is any device (from a microcontroller up to a full-fledged server) that runs an MQTT library and connects to an MQTT broker over a network.

Code a simple client

Create a project

We need to create a console project I use dotnet CLI to create a new project

dotnet new console --name SimpleMQTTClient

Now We have a new empty project ๐Ÿ˜.

Install dependency

For working in dotnet with MQTT we need to install the MQTTnet.Extensions.ManagedClient package from NuGet.

dotnet add package MQTTnet.Extensions.ManagedClient --version 3.1.1

At this time last stable version of MQTTnet is 3.1.1.


Now it's time to have some fun in code. Open Program.cs

using MQTTnet;
using MQTTnet.Client.Connecting;
using MQTTnet.Client.Disconnecting;
using MQTTnet.Client.Options;
using MQTTnet.Extensions.ManagedClient;
using System.Text.Json;

// Create the client object
IManagedMqttClient _mqttClient = new MqttFactory().CreateManagedMqttClient();

// Create client options object
MqttClientOptionsBuilder builder = new MqttClientOptionsBuilder()
ManagedMqttClientOptions options = new ManagedMqttClientOptionsBuilder()

// Set up handlers
_mqttClient.ConnectedHandler = new MqttClientConnectedHandlerDelegate((e) => Console.WriteLine("Connected"));
_mqttClient.DisconnectedHandler = new MqttClientDisconnectedHandlerDelegate((e) => Console.WriteLine("Disconnected"));
_mqttClient.ConnectingFailedHandler = new ConnectingFailedHandlerDelegate((e) => Console.WriteLine("Connection failed check network or broker!"));

// Connect to broker
await _mqttClient.StartAsync(options);

// Send a new message to the broker every second
while (true)
    string json = JsonSerializer.Serialize(new { message = "Hi Mqtt", sent = DateTime.UtcNow });
    await _mqttClient.PublishAsync("", json);

    await Task.Delay(TimeSpan.FromSeconds(1));

By default MQTT without encryption port is 1883 if you want to change it add a parameter port number to WithTcpServer like

// Create client options object
MqttClientOptionsBuilder builder = new MqttClientOptionsBuilder()


You have an MQTT client. I hope it was useful. In this post, I will show you how to create a broker to test it.

You find this project on Github.

If you are still unsure of what to do or if you got any errors, I suggest you use the comment section below and let me know! Iโ€™m here to help.


A new version of the MQTT library for DotNet was released recently, which introduced many breaking changes, so that you can read the article about it on this page.