Moryx.AspNetCore.Mqtt 10.10.1

The goal:

The goal is to allow any MORYX developer to create their own Mqtt To MORYX facade, that way you can use Mqtt to communicate with any MORYX facade like: ProductManagement,ResourceManagement etc.

To achieve that, we took inspiration from 3 repositories:

• Hosted Mqtt Server
• How to use Mqtt as a service in asp.net controller
• Mqtt AttributeRouting

Checking those repositories will give you an idea of what the ManagedMqtt is trying to achieve.

1. APIs and classes:

   IManagedMqttClient A managed IMqttClient IMqttService : Preferred base class for all services based on Mqtt . IMqttEndpoint : Mqtt Endpoint interface. Every endpoint will implement this interface.

2. Usage:

   To use the IManagedMqttClient you need to configure it in the Program.cs like so:

   builder.Services.AddMqttClient();
   

   Optionally you can also configure the Mqtt client connection details like so:

   builder.Services.AddMqttClient((provider, options) =>
   {
       options.Connection = new MqttConnectionConfig
       {
           Port = 1883,
           Id = "EndpointDemo1",
           Host = "localhost",
           QoS = MQTTnet.Protocol.MqttQualityOfServiceLevel.ExactlyOnce,
           RootTopic = "mqtt/moryx"
       };
       // optional: add your custom converter/serializer
       options.JsonSerializerOptions.Converters.Add(new MyConverter())
   })
   

   You can also configure the Mqtt client using a configuration file just like any MORYX module. The configuration file can be found inside the default MORYX Config folder. The content is as follows:

   {
     "Id": "my-id",
     "Host": "localhost",
     "Port": 1883,
     "Username": null,
     "Password": null,
     "Tls": false,
     "QoS": "ExactlyOnce", // check the MqttQualityOfServiceLevel enum for more info
     "ReconnectDelayMs": 30000,
     "ReconnectWithClientSession": false,
     "RootTopic":  ""
   }
   

3. Serialization :

   The serialization of payload is done via MqttMessageSerialization helper class, serialization and deserialization methods requires JsonSerializerOptions that is configured during setup of the Mqtt client.

4. JsonSerializationOptions :

   // Program.cs
   builder.Services.AddMqttClient(builder: (provider, options) =>
   {
       options.JsonSerializerOptions.Converters.Add(new MyCustomConverter()) // here you add your custom converter
       options.JsonSerializerOptions.ReferenceHandler = ReferenceHandler.IgnoreCycles; // change how references are handled
       //etc..
   })
   //.. other code
   

   If you want to implement your custom service based on the IManagedMqttClient the recommended way is the following:

   • In your Program.cs add the following:

   builder.Services.AddMqttClient(); // this adds the IManagedMqttClient to the service collection
   

   • Create a new C# class and inherit from IMqttService. Note: Dependency injection is supported. Now your service has access to the IManagedMqttClient.

   To add your new service to the service collection do the following:

   builder.Services.AddMqttClient();
                   .AddMqttService<BlablaService>(); // you custom service
   

   Note : the connection to the broker (Connect, re-connect on connection lost etc...) is automatically handled by the IManagedMqttClient.

5. Endpoints :

   If you need something with topic template and constraint support, you can use the IMqttEndpoint. Here is an example:

   • In your program.cs add the following:

   builder.Services.AddMqttClient() // must be present
                   .AddMqttEndpoints(); // <-- this adds supports for the endpoints
   

   • Create a new C# class that implements the IMqttEndpoint Example.

   There is a minimal version of the Mqtt endpoint, that you can use directly in the Program.cs:

   builder.Services.AddMqttClient()
                   .AddMqttEndpoints(route =>
                   {
                       route.MapGet("my-topic/{id:int}/method/{methodName}", context =>
                       {
                           var messageBuilder = new MqttApplicationMessageBuilder();
                           messageBuilder.WithTopic("another-topic");
                           messageBuilder.WithPayload(MqttMessageSerialization.GetJsonPayload("Hello World!!!!"));
                           return messageBuilder.Build();
                       });
                       // optional : this behave like an eventStream
                       route.MapPost(stream =>
                       {
                           var messageBuilder = new MqttApplicationMessageBuilder();
                           messageBuilder.WithTopic("another-topic");
                           var timer = new Timer(async arg =>
                           {
                               var messageBuilder = new MqttApplicationMessageBuilder();
                               messageBuilder.WithPayload(MqttMessageSerialization.GetJsonPayload("Hello World!!!!"));
                               var message = messageBuilder.Build();
                               await stream.WriteAsync(message);
                           }, null, 0, 10 * 1000);
                       });
                   });
   

   This can be useful for quick prototyping and testing.

6. Available features in endpoints :

   Endpoints topics support constraint just like in ASP.net controller route.

7. Route constraint :

   Find the list of available constraints Here

8. Message Body and Parameters inside a Topic :

   When the endpoint receives a message from the broker, it might come with a Body(payload) and a parameter inside the topic. To access the payload inside your endpoint you can use one of the following methods:

   FromBody<T>(string propertyName)
   

   FromBody(string propertyName, Type type)
   

   //Return the entire body of the request cast to the given type T
   RequestBody<T>()
   

   //Get the request body as an Object
   RequestBodyObject()
   

More resources:

1. Mqtt Services
2. Managed Mqtt