For comunication with arduino this tutorial uses Orion Context Broker of the Fiware tecnologies. The Fiware platform include open source software enablers that allow easy development of Smart cities and IoT solutions. You may find more informations on the following links: https://www.fiware.org/ http://catalogue.fiware.org/enablers/publishsubscribe-context-broker-orion-context-broker
The Orion Context Broker is an implementation of the Publish/Subscribe Context Broker GE, providing the NGSI9 and NGSI10 interfaces. This interfaces uses the REST-API to accept update and query commands for wirte and read operations. The following figure presents the schematic architecture of our tutorial, where Arduino sends NGSI notifications by ESP8266 module to Orion Context Broker allowing applications subscriptions.
Tutorial of the Hackester.io: https://www.hackster.io/user425778085/arduino-and-fiware-technology-13462a?ref=user&ref_id=100238&offset=0