MQTT and Node.js

Messaging in the Internet of Things

@matteocollina

MQTT

• publish/subscribe protocol
• multiple quality of service level..
• ..with at-least-once and exactly-once semantics
• low overhead (2 bytes at minimum)
• offline messaging
• retained messages, like a key/value store

Why Node.js matters?

• high performance (2x at Paypal)
• faster application development (2x at PayPal)
• batteries not included
• go check out  http://www.nearform.com/nodecrunch/node-js-becoming-go-technology-enterprise

• Almost 70.000 modules
• 3.685.510 module downloaded per day
• Exponential growth
• Permissive licenses
• How to spot a good module?

http://500px.com/photo/64986565  

MQTT.js

• 20k packets/second parser
• Stream based
• High-Level Client API
• Low-Level Server
• Build with  by @adamvr and @mcollina

Instant Gratification

var client = mqtt.createClient();

client.subscribe("mqtt/demo");

client.on("message", function(topic, payload) {
  alert([topic, payload].join(": "));
  client.end();
});

client.publish("mqtt/demo", "hello world!");

Pattern Matching

var client = mqtt.createClient();

client.subscribe("mqtt/+");

client.on("message", function(topic, payload) {
  alert([topic, payload].join(": "));
  client.end();
});

client.publish("mqtt/demo", "hello world!");

Mosca

MQTT broker in Node.js

• http://npm.im/mosca
• Standalone usage, through `$ mosca`
• Embeddable in your app
• Authentication APIs
• Supports AMQP, Mongo, Redis, and MQTT as pub/sub backends
• Needs a DB, such as LevelDB, Mongo, or Redis
• Support websockets
• Fast, 10k+ messages routed per second
• Scalable, 10k+ concurrent connections

How can it work on a Browser?

• Works on top of WebSocket
• Node.js excels at that :)
• MQTT over Websocket is 'standard'
• uses test broker at test.mosca.io
• Thanks to @substack for Browserify

Benchmark

Offline Mode

First, subscribe with QoS 1 and disconnect

var client = mqtt.createClient({
  clientId: "moscaslides",
  clean: false
});

client.subscribe("mqtt/offline", { qos: 1 },
  function() {
  
  alert("subscribe done!");
  // called when the subscribe is successful
  client.end();
});

Offline Mode

Then, someone else publish an important message

var client = mqtt.createClient();

client.publish("mqtt/offline", "hello world!", {qos:1},
  function() {
  
  alert("publish done!");
  client.end();
});

Offline Mode

Reconnect to receive the missed messages

var client = mqtt.createClient({
  clientId: "moscaslides",
  clean: false
});

client.on("message", function(topic, payload) {
  alert([topic, payload.toString()].join(": "));
  
  setTimeout(client.end.bind(client), 1000);
});

Does Offline Mode Scale?

Ponte API

• http://<your ponte>/resources/<your thing>
• coap://<your ponte>/r/<your thing>
• mqtt(s)://<your ponte>/<your thing>

Thanks!

If you need help with node.js:

hello@matteocollina.com

@matteocollina on Twitter

www.matteocollina.com