library/org.meshtastic.mqtt/PublishProperties

PublishProperties

data class PublishProperties(val messageExpiryInterval: Long? = null, val topicAlias: Int? = null, val contentType: String? = null, val responseTopic: String? = null, val correlationData: ByteString? = null, val payloadFormatIndicator: Boolean = false, val userProperties: List<Pair<String, String>> = emptyList(), val subscriptionIdentifiers: List<Int> = emptyList())

MQTT 5.0 properties that can accompany a PUBLISH packet (§3.3.2.3).

All fields are immutable — ByteString for binary data and defensive list copies. Properties that are null are not present on the wire; the broker and client treat absent properties as "not specified" (which is distinct from zero/empty).

Constructors

PublishProperties

constructor(messageExpiryInterval: Long? = null, topicAlias: Int? = null, contentType: String? = null, responseTopic: String? = null, correlationData: ByteString? = null, payloadFormatIndicator: Boolean = false, userProperties: List<Pair<String, String>> = emptyList(), subscriptionIdentifiers: List<Int> = emptyList())

Properties

contentType

val contentType: String?

MIME type of the payload (e.g. "application/json", "text/plain"). Informational only — the broker does not interpret this value.

correlationData

val correlationData: ByteString?

Opaque binary data used to correlate a response with its original request when using the request/response pattern.

messageExpiryInterval

val messageExpiryInterval: Long?

Lifetime of the message in seconds. After this interval, the broker discards the message if it has not been delivered. Range: 0..4,294,967,295. null means the message does not expire.

payloadFormatIndicator

val payloadFormatIndicator: Boolean

If true, indicates the payload is UTF-8 encoded text. If false (default), the payload format is unspecified (treated as raw bytes).

responseTopic

val responseTopic: String?

The topic that the receiver should publish its response to, enabling the MQTT 5.0 request/response pattern (§4.10).

subscriptionIdentifiers

val subscriptionIdentifiers: List<Int>

Identifiers of the subscriptions that caused this message to be delivered (set by the broker, not the publisher). Each value is in the range 1..268,435,455.

topicAlias

val topicAlias: Int?

A numeric alias for the topic name, used for header compression to reduce bandwidth on repeated publishes to the same topic. Range: 1..65,535.

userProperties

val userProperties: List<Pair<String, String>>

Application-defined key-value string pairs. Keys may repeat. These are forwarded from the publisher to the subscriber unchanged.