QoS

Quality of Service levels for MQTT message delivery per §4.3.

QoS determines the delivery guarantee between the client and broker:

AT_MOST_ONCE (0): Best-effort, no acknowledgement. Messages may be lost.
AT_LEAST_ONCE (1): Guaranteed delivery via PUBACK. Messages may be duplicated.
EXACTLY_ONCE (2): Guaranteed single delivery via the 4-step PUBLISH → PUBREC → PUBREL → PUBCOMP handshake.

Higher QoS levels have higher overhead. Choose the level appropriate for your use case: telemetry data tolerates AT_MOST_ONCE, while financial transactions require EXACTLY_ONCE.

Entries

AT_MOST_ONCE

At most once delivery (QoS 0) — fire and forget.

AT_LEAST_ONCE

At least once delivery (QoS 1) — acknowledged delivery.

EXACTLY_ONCE

Exactly once delivery (QoS 2) — assured delivery via 4-step handshake.

Types

Companion

object Companion

Properties

entries

val entries: EnumEntries<QoS>

Returns a representation of an immutable list of all enum entries, in the order they're declared.

name

expect val name: String

ordinal

expect val ordinal: Int

value

val value: Int

The numeric QoS level (0, 1, or 2) as encoded on the wire.

Functions

valueOf

fun valueOf(value: String): QoS

Returns the enum constant of this type with the specified name. The string must match exactly an identifier used to declare an enum constant in this type. (Extraneous whitespace characters are not permitted.)

values

fun values(): Array<QoS>

Returns an array containing the constants of this enum type, in the order they're declared.