System.Net.Mqtt client sample

mqttclient.cs

//Note that you can set more properties and also not set the port, 
//in which case the MQTT default will be used
var configuration = new MqttConfiguration { Port = 55555 };
//Creation of the MQTT client
var client = await MqttClient.CreateAsync("192.168.1.29", configuration);

//MQTT connection of the client. You can pass optional args to the 
//ConnectAsync method and credentials
await client.ConnectAsync(new MqttClientCredentials("testClient"));

//MQTT subscription to a topic. This only performs the protocol subscription,
//which means that at this point it can start receiving messages from the Broker to that topic
await client.SubscribeAsync("foo/bar/topic", MqttQualityOfService.AtLeastOnce);

//Rx Subscription to receive all the messages for the subscribed topics
client.MessageStream.Subscribe(msg =>
{
    //All the messages from the Broker to any subscribed topic will get here
    //The MessageStream is an Rx Observable, so you can filter the messages by topic with Linq to Rx
    //The message object has Topic and Payload properties. The Payload is a byte[] that you need to deserialize 
    //depending on the type of the message
    Console.WriteLine($"Message received in topic {msg.Topic}");
});

//Rx subscription sample to only receive the messages 
//to a specific topic (using System.Reactive.Linq)
client
    .MessageStream
    .Where(msg => msg.Topic == "foo/bar/topic")
    .Subscribe(msg => Console.WriteLine($"Message received in topic foo/bar/topic"));

//MQTT publish to a topic
//The message has a topic and the payload in byte[], which you are in charge of serializing from the original format
//The PublishAsync method has some optional args
var message = new MqttApplicationMessage("test/topic", Encoding.UTF8.GetBytes("Test String  Message"));

await client.PublishAsync(message, MqttQualityOfService.AtLeastOnce);

//Method to unsubscribe a topic or many topics, which means that the message will no longer
//be received in the MessageStream anymore
await client.UnsubscribeAsync("foo/bar/topic");

//MQTT disconnection. Note that by now each client instance lifetime is from Connection to Disconnection
//You can't re use an instance or re connect once you disconnected. You will need to create another MqttClient instance
//This is currently reported as an issue and will be fixed for the next public version
await client.DisconnectAsync();