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MQTT Introduction
6
MQTT Introduction
Features
- IoT Message Protocol
- On Top of TCP
- Minimal overhead
- Simple
- Reliable communication
Light MQTT
MQTT
https://swf.com.tw
Heavy HTTP
HTTP
https://swf.com.tw
Simple
History
Agnostic
Quality
1999, Arlen Nipper and Andy Standford-Clark invent for monitoring oil pipeline
History
Session
Lightweight
Characteristic
- Binary
- Bi-direction
- Scalable
- Agnostic
- Push communication
- Heart beat mechanism
Pub / Sub
- Space decoupling
- Time decoupling
- Synchronisation decoupling
- Scalability
- Cluster broker
Pub / Sub
Pub / Sub
https://swf.com.tw
Message Queue ?
- Message must be consumed
- Message could be consumed by multiple consumer
- Easy build topic
Message Queue ?
https://www.hivemq.com/blog/mqtt-essentials-part2-publish-subscribe/
QoS
- QoS 0: At must once (PUBLISH)
- QoS 1: At least once (PUBLISH, PUBACK)
- QoS 2: Exactly once (PUBLISH, PUBREC, PUBREL, PUBCOMP)
QoS
https://swf.com.tw
Client / Server
Connection Establish
Connection
Establish
- Client - any devices using MQTT protocol connect to broker over network
- Broker - receive / filter / dispatch messages and authentication
Client / Broker
https://www.hivemq.com/blog/mqtt-essentials-part-3-client-broker-connection-establishment/
clientId
cleanSession must be true when empty clientId
CONNECT
cleanSession
Broker doesn't store client subscribed message
CONNECT
Will Message
This message notifies other clients when a client disconnects ungracefully
https://www.hivemq.com/blog/mqtt-essentials-part-3-client-broker-connection-establishment/
keepAlive
Client send regular message to broker
sessionPresent
tell client whether boker has a persistent session available
CONNACK
https://www.hivemq.com/blog/mqtt-essentials-part-3-client-broker-connection-establishment/
returnCode
CA
generate rsa ca.key
generate ca.crt by ca.key
Security Connection
Server
generate rsa server.key
generate server.crt by CA sign server.key
Security Connection
Client
CA certificate server rsa key
https://mcuoneclipse.com/2017/04/14/introduction-to-security-and-tls-transport-security-layer/