Introducing Vert.x MQTT client

In this ar­ti­cle, we will see how to set up the new Vert.x MQTT client. Ac­tu­ally, I have a real ex­am­ple so you can try it quickly.

If you are using Maven or Gra­dle, add the fol­low­ing de­pen­dency to the de­pen­den­cies sec­tion of your project de­scrip­tor to ac­cess the Vert.x MQTT client:

• Maven (in your pom.xml):

<dependency>
    <groupId>io.vertx</groupId>
    <artifactId>vertx-mqtt</artifactId>
    <version>3.5.0.Beta1</version>
</dependency>

• Gra­dle (in your build.gra­dle file):

dependencies {
  compile 'io.vertx:vertx-mqtt:3.5.0.Beta1'
}

Now that you’ve set up your project, you can cre­ate a sim­ple ap­pli­ca­tion which will re­ceive all mes­sages from all bro­ker chan­nels:

import io.vertx.core.AbstractVerticle;
import io.vertx.mqtt.MqttClient;
import io.vertx.mqtt.MqttClientOptions;

import java.io.UnsupportedEncodingException;

public class MainVerticle extends AbstractVerticle {

  @Override
  public void start() {
     MqttClientOptions options = new MqttClientOptions();
      // specify broker host
      options.setHost("iot.eclipse.org");
      // specify max size of message in bytes
      options.setMaxMessageSize(100_000_000);

    MqttClient client = MqttClient.create(vertx, options);

    client.publishHandler(s -> {
      try {
        String message = new String(s.payload().getBytes(), "UTF-8");
        System.out.println(String.format("Receive message with content: \"%s\" from topic \"%s\"", message, s.topicName()));
      } catch (UnsupportedEncodingException e) {
        e.printStackTrace();
      }
    });

    client.connect(s -> {
      // subscribe to all subtopics
      client.subscribe("#", 0);
    });
  }
}

The pub­lish­Han­dler is the han­dler called each time the bro­ker, lo­cated at iot.eclipse.org:1883, sends a mes­sage to you, from the top­ics you are sub­scrib­ing for.

But only pro­vid­ing a han­dler is not enough, you should also con­nect to the bro­ker and sub­scribe to some top­ics. For this rea­son, you should use the con­nect method and then call sub­scribe when the con­nec­tion es­tab­lished.

To de­ploy this ver­ti­cle from an ap­pli­ca­tion you should have in your main method some­thing like that:

Vertx vertx = Vertx.vertx();
vertx.deployVerticle(MainVerticle.class.getCanonicalName());

When you have com­pleted all steps cor­rectly the re­sult should look like that:

As the al­ter­na­tive and rec­om­mended way to boot­strap Vert.x ap­pli­ca­tions you can use vertx-​maven-starter or vertx-​gradle-starter. For com­plet­ing this guide I have used the first one. The final source code avail­able here. If you would like to learn more about Vert.x MQTT client API then check out the full doc­u­men­ta­tion and more ex­am­ples.

Thank you for read­ing!

Cheers!