A structure representing the payload and attributes of an MQTT message. The message topic is not part of this structure (see MQTTClient_publishMessage(), MQTTClient_publish(), MQTTClient_receive(), MQTTClient_freeMessage() and MQTTClient_messageArrived()).
The eyecatcher for this structure. must be MQTM.
The version number of this structure. Must be 0
The length of the MQTT message payload in bytes.
A pointer to the payload of the MQTT message.
The quality of service (QoS) assigned to the message. There are three levels of QoS:
The retained flag serves two purposes depending on whether the message it is associated with is being published or received.
retained = true
For messages being published, a true setting indicates that the MQTT server should retain a copy of the message. The message will then be transmitted to new subscribers to a topic that matches the message topic. For subscribers registering a new subscription, the flag being true indicates that the received message is not a new one, but one that has been retained by the MQTT server.
retained = false
For publishers, this ndicates that this message should not be retained by the MQTT server. For subscribers, a false setting indicates this is a normal message, received as a result of it being published to the server.
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 message identifier is normally reserved for internal use by the
MQTT client and server.