Part 14 of the OPC UA Standard, aka "Publish-Subscribe" or "PubSub," was released in early 2018, helping to encourage further interaction between OPC UA and communication protocols such as MQTT. According to the OPC Foundation, "PubSub enables the use of OPC UA directly over the Internet by utilizing popular data transports like MQTT (Message Queuing Telemetry Transport) and AMQP (Advanced Message Queuing Protocol), while retaining key OPC UA end-to-end security and standardized data modeling advantages."

The standard has also aided in the advancement of communication capabilities in IoT devices such as gateways. IoT gateways connect an on-premises communications network to a cloud-based communications network. IoT gateways, also known as "Edge devices," provide data connectivity to sensors and end-devices completely on-premises. They also include a communication path that connects the device to the cloud. Intelligent, programmable devices of today perform in-depth and complex processing on IoT data, acting as full-fledged computing platforms running modern operating systems (for example, Linux or Windows).

Because of the increase in processing power, memory, and storage, as well as intelligent “middleware” encompassing key features such as protocol translators, data buffering, edge analytics, on-premise visualization, and cloud enablement, such systems are sometimes referred to as “intelligent gateways.”
Message Queuing Telemetry Transport (MQTT) is a protocol designed specifically for collecting data from multiple devices and transporting it to the IT infrastructure. Because it is lightweight, it is ideal for remote monitoring, particularly in M2M connections that require a small code footprint or have limited network bandwidth. It employs a publish/subscribe mechanism to reduce payload and overhead when working with application-specific, custom JSON or binary formats. MQTT is widely used in IT departments all over the world.

IoTWorX, ICONICS’ gateway software suite, supports MQTT in a variety of ways. The gateway has the ability to publish data to a MQTT Broker. The published data can be sent using JSON encoding, with the payloads being user-customizable. Along with the data values, the user can specify what information is sent (timestamp, quality). Alternatively, the published data can be sent in an ICONICS standard format designed for communicating with an ICONICS system.

Such a system could be embedded in any cloud that supports MQTT communications. ICONICS’ standard method allows for the sending of additional properties such as Descriptions and Ranges, as well as the sending of only changed values, which can improve communications efficiency.

IoTWorX can subscribe to MQTT data as well as publish data over MQTT. This enables the gateway to receive data via MQTT from third-party devices. The payloads of the MQTT messages it receives must be encoded in JSON. The contents of the messages, on the other hand, are user-customizable. That is, the user can choose which properties (timestamp, quality) to include in the messages along with the data values. The communications, like the other MQTT communication options, can be encrypted and secured using X.509 certificates.

OPC UA: Reliable, Safe, and Scalable

OPC UA is the result of a multi-year collaboration between industry leaders to develop an open standard for exchanging information in a rich, object-oriented, and secure manner. This standard addresses the fundamental need for mapping and exchanging real-world data in a platform-independent manner while remaining compatible with the OPC Classic specifications.

OPC UA is a robust, secure, and scalable extension of the highly successful OPC standard communication protocol based on COM/DCOM. It allows best-of-breed, real-time alarm management and historian systems to communicate with one another. This enables a consistent model of plant floor integration with the enterprise.