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Basic MQTT with C#

Eduardo Julião on July 04, 2021

In this post, we're going to have a look on how to work with MQTT and Csharp. Creating a Broker and a Client that sends data to it. But first... ...
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Simon (Darkside) Jackson •

Great example and got me going quick and simple. Needs updating to the latest version of mqtt, but a fantastic start.

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David Jones •

This is a clear and simple guide for getting started with MQTTnet, Thanks.
I am looking at using it for sending Telemetry to an Azure IoT Hub. The only chenages I have made thus far are:

                MqttClientOptionsBuilder builder = new MqttClientOptionsBuilder()
                                        .WithClientId(Secrets.deviceId)
                                        .WithTcpServer(Secrets.IOT_CONFIG_IOTHUB_FQDN, 8883);
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IOT_CONFIG_IOTHUB_FQDN is of the form HUB_NAME.azure-devices.net
It "works" OK but doesn't report connect/non connection, but doesn't fail.
Does report non connection if incorrect Hub FQDN is used.

I understand I have to create a secure connection using the SAS key or connection string.
Any ideas of how to proceed? I can manually get the SAS key so can skip that code.

Thx in advance.

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David Jones •

Nb: Can attempt to send messages. They do get queued.

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David Jones • • Edited

Have improved my code. Got to work out Authentication:

                MqttClientOptionsBuilder builder = new MqttClientOptionsBuilder()
                                        .WithClientId(Secrets.deviceId)
                                        .WithTls()
                                        //.WithAuthentication( )
                                        .WithTcpServer(Secrets.IOT_CONFIG_IOTHUB_FQDN, Secrets.MqttPort);
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nhatanhni •

thanks

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QT •

Thanks for this code example! 👍

In github code, you have ApplicationMessageReceivedHandler which is probably never called in this sample. (not working for me localy)

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codemaker •

Nice article, Could you please give tutorial or article on enabling TLS on MQTT communication? also explain more on port 8883. It helps

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thanhdt2782 •

Thanks.

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simonong •

Hi: Is there anyway to poll the Topic and payload instead of using event?
or the broker will send the message periodically ?

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Hassan Elgamily •

How to connect Client to Broker remotely on two different devices?

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Ricardo •

According to the documentation there are multiple protocol communication you can use, such as websocket, socket and even http.

Check out the documentation for more details