The document provides an overview of pub/sub messaging, specifically focusing on the MQTT protocol, including key properties, quality of service levels, retained messages, persistent sessions, and security measures. It outlines various pub/sub brokers, both open-source and cloud-based, as well as client libraries and demo setups. Additionally, it includes references for further reading and exploration of the topic.

1. Pub/Sub Messaging
Peter Hanzlík
peterhanzlik@gmail.com

2. Source: http://imgs.xkcd.com/comics/standards.png

4. What is Pub/Sub Messaging

5. Real Example

6. ISO/OSI

7. Common Properties
• Minimal Overhead (Low Bandwidth)
• Real-time (Low Latency)
• Push instead of Pull
• Reliable (even in Unreliable Networks)

8. Topic
• At least 1 character
• May include spaces
• Case-sensitive

9. Topic Filtration - Wildcards
Note: Cannot be used for Publish

10. Quality of Service
QoS 0 | At most once
QoS 1 | At least once
QoS 2 | Exactly once
* Applies to MQTT protocol only, other
protocols implement similar QoS options

11. Retained Messages
• Last known good value for the specified topic
• Every time a new client subscribes to that specific topic, it will
instantly receive the last retained message on that topic
• Any message may be send as retained

12. Last Will & Testament (LWT)
• Defined at the connection to the broker
• When client disconnects unexpectedly, broker sends this message on
clients behalf

13. Persistent Session
• Broker stores session information including:
• All subscriptions of the client
• All QoS 1 / 2 messages which are not processed yet
• All QoS 1 / 2 messages the client missed while being offline

14. Bridge
• Message forwarding
• Direction: in | out | both
• Broker behaves like a client to another broker
• Bridge handled by Broker, not by protocol

15. Security
• Username / Password (ACL, DB, LDAP)
• SSL/TLS (X509), SASL
• OAuth 2, Kerberos, OpenID Connect, …
• Payload encryption/signing

16. MQTT
• Easy and Lightweight
• Data agnostic (Message centric)
• Binary
• Open

17. AMQP
• Queue Federation, Load Balancing, Advanced Security (SASL)
• ISO/IEC Standard
• PCI DSS Compatible (IT Audit)

18. Architecture Cloud 1 Cloud 2
MQTT MQTT MQTT MQTT
AMQP AMQP
AMQP
Site 1 Site 2

19. DDS – Data Distribution Service
• Decentralized
• Dynamic Discovery
• Real-time
• High-performance
• Advanced Security
• Data Centric

20. Pub/Sub Brokers Examples
• Mosquitto:
• MQTT
• Open-source
• WebSocket support
• HiveMQ:
• MQTT
• High-performance
• Clustering
• Enterprise Solution
• WebSocket support
• RabbitMQ:
• AMQP
• Plugins: MQTT, STOMP
• Apache ActiveMQ:
• JMS
• Plugins: MQTT, AMQP, STOMP
• IBM WebSphere MQ

21. Pub/Sub Brokers – Cloud Based
• CloudMQTT.com (Mosquitto)
• CloudAMQP.com (RabbitMQ)
• Google Cloud Messaging
• Amazon SNS (Simple Notification
Service)
Test Brokers:
• broker.mqttdashboard.com (Hive MQ)
• test.mosquitto.org (Mosquitto)
• iot.eclipse.org (Mosquitto)

22. Pub/Sub Client Libraries – MQTT Examples
• Arduino
• NodeMCU
• mbed
• MQTT.js
• ruby-mqtt
• Mosquitto-PHP
• Eclipse Paho (C, C++, Java, Javascript, Python, Go, C#)

23. Demo 1
SSID: MQTT_Broker
Broker IP: 192.168.1.1
Broker Port: 1883 (default)
Authentication: none

24. Demo 2
MQTT Bridge
MQTT Bridge
STOMP
WebSocket
(Paho)
Arduino MQTT Client
NodeMCU MQTT
MQTT
HTTP

25. Q&A
Thank you for your attention

26. Reference
• http://www.hivemq.com/blog/mqtt-essentials-part-1-introducing-
mqtt
• http://www.prismtech.com/sites/default/files/documents/Messaging
-Whitepaper-040615_1.pdf
• https://azure.microsoft.com/en-us/documentation/articles/service-
bus-amqp-overview/
• https://github.com/knolleary/pubsubclient