Event arguments for MQTTClient::messageArrived.
The dup flag indicates whether or not this message is a duplicate. It is only meaningful when receiving QoS1 messages. When true, the client application should take appropriate action to deal with the duplicate message.
The handled flag must be set by the event delegate after processing of the message to indicate whether the message has been successfully processed. If set to false, the MQTT client will attempt to deliver the message again. The handled flag defaults to true. If the event delegate throws, the handled flag will be set to false by the framework. This means that in most cases the delegate does not need to concern itself with this flag.
The published message.
The topic the message has been published to.