MQTTMessage Type

An MQTT message.

Remarks

This type represents an MQTT message.

Fields

ContentType
String

String describing the content of the message. Defined by the sending and receiving application.

Valid only for MQTT 5.

CorrelationData
String

Used by the sender of the request message to identify which request the response message is for when it is received.

Valid only for MQTT 5.

Duplicate
Boolean

Whether or not this message's Duplicate flag is set.

Message
String

This message's raw data payload.

MessageB
Byte[]

This message's raw data payload.

MessageExpInterval
Integer

The lifetime of the message in seconds specified by the sender.

For outgoing messages, the value is useful for instructing the server to delete its copies of the message for any subscribers it has not been able to start delivery to.

For incoming messages, the value sent by the server is the lifetime specified by the sender minus the time the message has been waiting in the server.

Valid only for MQTT 5.

PacketId
Integer

This message's packet Id.

PayloadFormatIndicator
Integer

Indicates whether the payload is unspecified bytes or UTF-8 Encoded character data. Possible values are:

ValueDescription
0 Payload is unspecified bytes
1 Payload is UTF-8 Encoded Character Data

Valid only for MQTT 5.

QoS
Integer

This message's QoS level. Possible values are:

ValueDescription
0At most once delivery
1At least once delivery
2Exactly once delivery

ResponseTopic
String

String used as the topic name for a response message.

Valid only for MQTT 5.

Retained
Boolean

Whether or not this message's Retain flag is set.

State
Integer

This message's current state.

Possible Outgoing Message States:

ValueDescription
0 PUBLISH sent, waiting for PUBACK (QoS 1 only)
1 PUBLISH sent, waiting for PUBREC (QoS 2 only)
2 PUBREC received, sending PUBREL (QoS 2 only)
3 PUBREL sent, waiting for PUBCOMP (QoS 2 only)
4 Final acknowledgment received

Possible Incoming Message States:

ValueDescription
5 PUBLISH received, sending PUBACK (QoS 1 only)
6 PUBLISH received, sending PUBREC (QoS 2 only)
7 PUBREC sent, waiting for PUBREL (QoS 2 only)
8 PUBREL received, sending PUBCOMP (QoS 2 only)
9 Final acknowledgment sent

SubscriptionIdentifiers
String

A comma separated list of any SubscriptionIdentifiers associated with any client subscription(s) that caused this message to be delivered.

This field is only applicable to incoming messages.

If SubscriptionIdentifier is set when subscribing, it will be included in any messages delivered by the broker for the topics specified in that packet.

See the Subscribe method for more details.

Valid only for MQTT 5.

Topic
String

This message's topic.

MQTT 5 Notes:

If this value is empty, the TopicAlias field holds the assigned alias for the topic.

If this value is not empty and TopicAlias is non-zero,

TopicAlias
Integer

An integer used to identify the topic instead of the full topic filter in order to reduce the size of the publish packet.

If a non-zero topic alias is received, the client should establish a new topic alias mapping or use an existing mapping, depending on whether the Topic string is empty.

For details on setting topic aliases for outgoing messages, see the TopicAlias configuration setting.

Valid only for MQTT 5.

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