The OPC Unified Architecture (UA), released in 2008, is a platform independent service-oriented architecture that integrates all the functionality of the individual OPC Classic specifications into one extensible framework.
This multi-layered approach accomplishes the original design specification goals of:
- Functional equivalence: all COM OPC Classic specifications are mapped to UA
- Platform independence: from an embedded micro-controller to cloud-based infrastructure
- Secure: encryption, authentication, and auditing
- Extensible: ability to add new features without affecting existing applications
- Comprehensive information modeling: for defining complex information
My adjustable height desk [1] can now measure it's current height and announce it via MQTT thanks to a little NodeMCU script I whipped up and an HC-SR04 ultrasonic sensor connected to the ESP8266. Using mqttwarn [2] that data gets pushed into a Google Docs spreadsheet where I can then plot it easily.
QTT is a machine-to-machine (M2M)/"Internet of Things" connectivity protocol. It was designed as an extremely lightweight publish/subscribe messaging transport. It is useful for connections with remote locations where a small code footprint is required and/or network bandwidth is at a premium. For example, it has been used in sensors communicating to a broker via satellite link, over occasional dial-up connections with healthcare providers, and in a range of home automation and small device scenarios. It is also ideal for mobile applications because of its small size, low power usage, minimised data packets, and efficient distribution of information to one or many receivers
Mosquitto is an open source (BSD licensed) message broker that implements the MQ Telemetry Transport protocol versions 3.1 and 3.1.1. MQTT provides a lightweight method of carrying out messaging using a publish/subscribe model. This makes it suitable for "machine to machine" messaging such as with low power sensors or mobile devices such as phones, embedded computers or microcontrollers like the Arduino. A good example of this is all of the work that Andy Stanford-Clark (one of the originators of MQTT) has done in home monitoring and automation with his twittering house and twittering ferry. Andy gave a talk on this at OggCamp that explains a bit about MQTT and how he uses it. The slides and audio are available online at slideshare