question: protected void publish ( ) throws MqttException , IOException { sampleClientPub = new SampleAsyncCallback ( url , clientIdPub , cleanSession , quietMode , userName , password ) ; if ( sampleClientPub != null ) { String topic = "Sample/Java/v3" ; int qos = 2 ; String message = "Message from async calback MQTTv3 Java client sample" ; try { sampleClientPub . publish ( topic , qos , message . getBytes ( ) ) ; } catch ( Throwable e ) { e . printStackTrace ( ) ; } } }
target:  Publish / send a message to an MQTT server