What is MQTT and AMQP , What is the difference between them?

Overview

MQTT and AMQP are both messaging protocols used for communication between systems, but they are designed for very different use cases.

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MQTT (Message Queuing Telemetry Transport)

A lightweight publish/subscribe messaging protocol designed for IoT and constrained networks (low bandwidth, high latency, unreliable connections).

How MQTT Works

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Publisher (device) → [MQTT Broker] → Subscriber (app)
                    (e.g., Mosquitto, AWS IoT, HiveMQ)

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// Flutter MQTT client
import 'package:mqtt_client/mqtt_client.dart';
import 'package:mqtt_client/mqtt_server_client.dart';

final client = MqttServerClient('broker.hivemq.com', 'flutter_client');
client.port = 1883;

await client.connect();

// Subscribe to a topic
client.subscribe('sensors/temperature', MqttQos.atLeastOnce);

// Receive messages
client.updates!.listen((List<MqttReceivedMessage<MqttMessage>> messages) {
  final msg = messages[0].payload as MqttPublishMessage;
  final payload = MqttPublishPayload.bytesToStringAsString(msg.payload.message);
  print('Temperature: $payload');
});

// Publish message
final builder = MqttClientPayloadBuilder()..addString('25.5°C');
client.publishMessage('sensors/temperature', MqttQos.atLeastOnce, builder.payload!);

MQTT QoS Levels

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AMQP (Advanced Message Queuing Protocol)

A full-featured enterprise messaging protocol designed for reliable, transactional message queuing between business systems.

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Producer → [Exchange] → [Queue] → Consumer
            (RabbitMQ, Azure Service Bus, ActiveMQ)

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// AMQP in Flutter — via dart_amqp package
import 'package:dart_amqp/dart_amqp.dart';

final client = Client(settings: ConnectionSettings(
  host: 'rabbitmq.example.com',
  authProvider: PlainAuthenticator('user', 'password'),
));

final channel = await client.channel();
final queue = await channel.queue('order-processing');

// Publish a message
queue.publish('{"orderId": 123, "status": "PAID"}');

// Consume messages
await queue.consume().then((consumer) {
  consumer.listen((message) {
    print('Processing order: ${message.payloadAsString}');
    message.ack(); // Acknowledge processing
  });
});

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Key Differences

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When to Use Which

Summary: MQTT = lightweight IoT messaging. AMQP = enterprise-grade reliable messaging with routing, queues, and transactions.