alepha@docs:~/docs/.content/release/framework/docs/reference/providers$
cat MqttClientProvider.md | pretty
1 min read
Last commit:

#MqttClientProvider

#Import

typescript 
1import { MqttClientProvider } from "@alepha/mqtt";

#Overview

MQTT 5 client provider.

Low-level MQTT client for publish/subscribe messaging, analogous to RedisProvider: the transport that @alepha/mqtt/topic builds on. Payloads are bytes (string | Uint8Array out, Uint8Array in), so JSON, protobuf and Sparkplug all ride on it.

Dispatch by Subscription Identifier. Every broker subscription carries its own MQTT 5 Subscription Identifier, and a received message reaches only the subscriptions whose identifiers it carries. Matching by filter instead would hand a message received for $share/g/a/+ to a plain a/+ held by the same client too, and the copy received for a/+ to the group's callbacks, so a group handler would run twice, and run on an instance the broker did not pick. Under MQTT 3.1.1 (protocolVersion: 4) there are no identifiers: the client falls back to filter matching and refuses $share/.

Subclasses own the wire (sendPublish, sendSubscribe, sendUnsubscribe, the connection); this class owns the subscription registry, so the memory client and mqtt.js cannot disagree about it.