Building a conference attendee tracking system using DNN and MQTT Peter Donker DNN Connect 2017

First attempt at this using: Last Year First attempt at this using: Raspberry Pi HD44780 Display RFID Cards and Scanner Mono WebAPI calls to server

Quite a few reliability issues Last Year Quite a few reliability issues IoT app ran as console app Network was not reliable

Console App Because the card reader was a “USB keyboard” Cannot read keyboard in a background process So look for a reader that is not a keyboard

First Snag Could only find “good” code in Python/C for the RC522 chip In general: Python is the most ubiquitous for IoT code, then C Subsequently it is *very* hard to do dotnetcore dev for IoT

The old cards didn’t “work” Many different RFID standards (?!?) Another small snag ;-) The old cards didn’t “work” Many different RFID standards (?!?) 2016: low frequency EM4100 cards 2017: MiFare cards

Second challenge: network reliability We have to assume the network is not always up http web api calls (can be) relatively “demanding” Most common protocol used in these situations: MQTT

MQTT Message Queue Telemetry Transport Traces back to IBM in the 90’s. First standard in 1999. Focus on: limited bandwidth, reliability, simplicity TCP – Ports 1883 or 8883 (SSL) Widespread support

Follows so-called Pub-Sub pattern Message: MQTT Follows so-called Pub-Sub pattern Message: Topic (forward slash separated list) Message (agnostic what it is) QoS (0,1,2) Clients publish and subscribe to topics Everything runs through the “Broker” (i.e. the MQTT server) which does the dispatching of messages

MQTT From https://www.slideshare.net/BryanBoyd/mqtt-austin-api

MQTT From https://www.slideshare.net/BryanBoyd/mqtt-austin-api

MQTT Header size up to 2-4 bytes (pub), for HTTP: 100-1000 bytes Keep alive ping of 2 bytes Client libraries are typically small and available in many languages Simple to implement Easy to find commercially available brokers Reliable …

MQTT From https://www.slideshare.net/BryanBoyd/mqtt-austin-api

MQTT Gotchas: Security is on connection level, not topic level If you wish to have QoS > 0 then client must be able to reliably store queued messages

2017 Conference Tracking System Design Raspberry Pi Zero W Satellite 1 DNN Connect Server MQTT Conference Site (DNN) Satellite 2 Broker MQTT Satellite 3

2017 Conference Tracking System Design RFID DETECTOR Node Red Python http DNN Memory MQTT Broker DISPLAY

Demo time

Where one day DNN would incorporate a MQTT broker so I have a dream Where one day DNN would incorporate a MQTT broker so We can have devices and modules on par We can achieve a new level of extensibility Obstacles Use of non http protocol means it falls outside of IIS scope MQTT is per host – you’d need to solve multiple sites/portals