TLS MQTT broker connection using MqttClient

Last week I was working on a C# application to publish messages using the MqttClinet - https://m2mqtt.wordpress.com/using-mqttclient/

The IBM Watson IoT C# library use the same package :) https://github.com/ibm-watson-iot/iot-csharp

The library is amazing. However a few suggestions from my side:

1. The documentation is very generic, not explaining the complex scenarios.
2. The error codes are very generic and the documentation doesn't cover what the return error code number means.

The MQTT broker which we use is configured to use TLS. So, I was looking for a proper documentation to connect to the MQTT using TLS and I couldn't find one. So, I copy pasted the code we used for the connection:

var serverCert = new X509Certificate("certificte path *.cer");

//I  exported the certificate from the server and stored in a project folder.

            _client = new MqttClient("Host name", "port", true, serverCert, null - if you use client certificate, MqttSslProtocols.TLSv1_2);
            if (_client.Connect("Client name", "user name", "password") != 0)
            {
                throw new Exception("Unable to establish connection to MQTT broker");
            }

Clean code, better code

Last week I was working with my team to create a REST API for our sensor to publish data. At the time of writing, the sensor XDK we used supports only HTTP GET and we need a way to pass the temperature and acoustic data to our MQTT broker.

The quick and dirty suggestion is to create a WebAPI GET method and pass the message to our MQTT broker using M2Mqtt client.

This post, I don’t like to explain the implementation details, however I explain how neatly you can write the code.

The developer wrote the code like this

  [Route("publish")]

 public IHttpActionResult Get(string id, string noise, string temp){

              -compare mac id with database, if not throw error

              - convert noise to integer and find the noise level (low, medium or high based on the value matrix - a set of if else)

              -convert temperature to integer. Since the sensor returns mill-degree Celsius, convert it to Celsius

               - send data to MQTT using M2Mqtt

}

The controller contains > 200 lines code and it worked!!! I talked to the developer and asked, are you satisfied with the code you had written. He said it works well.

Then I explained the ways to organize the code

• Write a class for noise. All conversion (string to double) can be handled there. So the code is completely unit testable.
•   Create a class for temperature. Create properties for Degree Celsius, Fahrenheit…..
•   Create a NoiseRange class with max, min and "text" which specifies what that range means (refer Martin Fowler’s range pattern) and implement a method Includes (Noise noise) 
•  Create a NoiseManager class that contains the list of noise ranges (I've added noise ranges in a json file and stored in App_Data folder)
•  Create a repository pattern to interface with the data base (to verify the macid).
•  Create a MqttManager class to interface with the MQTT broker
•   Inject the repository, Noise Manager and MqttManager as dependencies. I prefer Autofac

Now each and every part of the program is modular and self-containing which can be unit tested individually

It takes some time to understand what a better clean code means. When you get it right, you always follow the right ritual. Happy coding !!!