📡

MQTT Integration

Combine ALEC compression with MQTT for efficient pub/sub IoT messaging. Reduce bandwidth by 90% while leveraging MQTT's reliability features.

Dependencies

[dependencies]
alec = "1.0"
rumqttc = "0.24"  # Or paho-mqtt, mosquitto-rs

Publisher (Sensor Side)

use alec::{Encoder, Context, Priority};
use rumqttc::{MqttOptions, Client, QoS};

fn main() {
    // ALEC setup
    let mut ctx = Context::new();
    let encoder = Encoder::new(&mut ctx);
    
    // MQTT setup
    let mut mqttoptions = MqttOptions::new("sensor-001", "broker.example.com", 1883);
    mqttoptions.set_keep_alive(Duration::from_secs(30));
    
    let (mut client, mut connection) = Client::new(mqttoptions, 10);
    
    // Sensor loop
    loop {
        let temperature = read_sensor();
        let msg = encoder.encode(temperature, Priority::Auto);
        
        // Map ALEC priority to MQTT QoS
        let qos = match msg.priority() {
            Priority::P1 | Priority::P2 => QoS::ExactlyOnce,
            Priority::P3 | Priority::P4 => QoS::AtLeastOnce,
            Priority::P5 => QoS::AtMostOnce,
        };
        
        client.publish("sensors/temp/001", qos, false, msg.as_bytes()).unwrap();
        
        thread::sleep(Duration::from_secs(10));
    }
}

Priority to QoS Mapping

P1/P2 → QoS 2 (Exactly Once) - Critical alerts must arrive
P3/P4 → QoS 1 (At Least Once) - Important data
P5 → QoS 0 (At Most Once) - Routine, loss acceptable

Subscriber (Server Side)

use alec::{Decoder, Context};
use rumqttc::{MqttOptions, Client, QoS, Event, Packet};

fn main() {
    let mut ctx = Context::new();
    let decoder = Decoder::new(&mut ctx);
    
    let (mut client, mut connection) = Client::new(mqttoptions, 10);
    client.subscribe("sensors/temp/#", QoS::AtLeastOnce).unwrap();
    
    for notification in connection.iter() {
        if let Event::Incoming(Packet::Publish(publish)) = notification {
            let value = decoder.decode(&publish.payload).unwrap();
            println!("Received: {}", value);
        }
    }
}

Recommended Topic Structure

sensors/
├── {device_id}/
│   ├── raw          # Full readings (P4)
│   ├── delta        # Delta-encoded (P5)
│   ├── alert        # Anomalies (P2)
│   └── critical     # Safety alerts (P1)
└── fleet/
    └── sync         # Context synchronization

Retained Messages

Use retained messages for context sync. New subscribers get the latest context state immediately.

Last Will

Configure LWT to notify when a sensor goes offline. Helps with fleet management.

Next Steps

LoRaWAN Guide Edge Computing