client.groovy

import groovy.transform.Field
import io.vertx.core.Vertx
import io.vertx.mqtt.MqttClient
import io.vertx.core.buffer.Buffer
import io.netty.handler.codec.mqtt.MqttQoS
@Field def MQTT_MESSAGE = "Hello Vert.x MQTT Client"
@Field def BROKER_HOST = "localhost"
@Field def MQTT_TOPIC = "/my_topic"
@Field def BROKER_PORT = 1883
def options = [
  keepAliveTimeSeconds:2
]

def client = MqttClient.create(Vertx.vertx(), options)


// handler will be called when we have a message in topic we subscribing for
client.publishHandler({ publish ->
  println("Just received message on [${publish.topicName()}] payload [${publish.payload().toString(java.nio.charset.Charset.defaultCharset())}] with QoS [${publish.qosLevel()}]")
})

// handle response on subscribe request
client.subscribeCompletionHandler({ h ->
  println("Receive SUBACK from server with granted QoS : ${h.grantedQoSLevels()}")

  // let's publish a message to the subscribed topic
  client.publish(MQTT_TOPIC, Buffer.buffer(MQTT_MESSAGE), MqttQoS.AT_MOST_ONCE, false, false, { s ->
    println("Publish sent to a server")
  })

  // unsubscribe from receiving messages for earlier subscribed topic
  vertx.setTimer(5000, { l ->
    client.unsubscribe(MQTT_TOPIC)
  })
})

// handle response on unsubscribe request
client.unsubscribeCompletionHandler({ h ->
  println("Receive UNSUBACK from server")
  vertx.setTimer(5000, { l ->
    client.disconnect({ d ->
      println("Disconnected form server")
    })
  })
})

// connect to a server
client.connect(BROKER_PORT, BROKER_HOST, { ch ->
  if (ch.succeeded()) {
    println("Connected to a server")
    client.subscribe(MQTT_TOPIC, 0)
  } else {
    println("Failed to connect to a server")
    println(ch.cause())
  }
})