mcp_io_mqtt

MQTT adapter for mcp_io — talk to IoT brokers (Mosquitto, HiveMQ, EMQX, AWS IoT, Azure IoT, …) through the same 4-Primitive surface used by the rest of the adapter family.

Capability matrix

Area Support
Protocol v3.1.1 (level 4) — Will, retain, persistent session, wildcards +/#
v5 codec Variable-byte integer, control packet types, 27 properties, reason codes (consumer of these decodes is wired into MqttCodec for callers)
Transport Pluggable MqttTransport; TCP plain / TLS / WebSocket (host project supplies the byte transport)
QoS 0 today; 1 / 2 PacketId tracker (InflightTracker + receiveMaximum reservation) shipped, full sequence wiring in progress
Topic filter +, # with full validation (last-segment-only #, no embedded wildcards)
Reason codes All v5 reason code → IoError mapping (mapping/reason_to_ioerror.dart)
Capabilities mqtt.publish, mqtt.subscribe, mqtt.unsubscribe, mqtt.set_will

Quick start

import 'package:mcp_io_mqtt/mcp_io_mqtt.dart';

final adapter = MqttAdapter(
  deviceId: 'broker-1',
  clientId: 'my-client',
  transport: InMemoryMqttTransport(), // production: TCP / TLS / WS
);
await adapter.connect();

// Capability-id flow (0.2.0+).
await adapter.execute(const Command(
  action: 'mqtt.publish',
  target: 'sensors/room1/temperature',
  args: {'payload': '21.5', 'retain': true},
));

final stream = adapter.subscribe(const TopicSpec(uri: 'sensors/+'));
stream.listen((env) => print('${env.uri}: ${env.payload.value}'));

Will (Last Will and Testament)

Set the will before connect() — the codec emits it inside the CONNECT packet. Calling mqtt.set_will once already connected is rejected.

await adapter.execute(const Command(
  action: 'mqtt.set_will',
  target: '',
  args: {
    'topic': 'status/my-client',
    'payload': 'offline',
    'qos': 1,
    'retain': true,
  },
));
await adapter.connect();

License

MIT — see LICENSE.

Libraries

mcp_io_mqtt
MQTT v3.1.1 + v5 adapter for mcp_io.