The CygNet OPC UA Server is a Windows service application installed on a host computer in a SCADA data center, which exposes CygNet data to OPC UA client applications. The server communicates with a CygNet system to request and receive encrypted data via HTTPS using via our flexible intermediary REST API application, CygNet Bridge API.

The diagram to the right demonstrates this architecture.

The CygNet OPC UA Server supports the following communication methods for exchanging CygNet data over a secure network connection:

• Client/Server — a request-response model where an OPC UA client makes requests for data and the OPC UA server returns with a response
• Pub/Sub — a publish-subscribe model where an OPC UA client establishes a subscription to data and then any changes will be published by the OPC UA server

The CygNet OPC UA server accesses CygNet data via CygNet Bridge and uses the Bridge API to authenticate access and provide the following types of CygNet data:

• Real-time values from the Current Value Services
• Historical values from the Value History Service
• Facility record and attributes from the Facility Service
• Point records and attributes from the Point Service
• Current alarms from the Common Alarm Service

CygNet OPC UA Server Licensing

The CygNet OPC UA Server is a separately licensed component from existing CygNet SCADA software components. A valid license file is required containing the appropriate OPC UA license component. The OPC UA Server will perform a license check that the OPC UA license component is active in the license file.

A CygNet Bridge license is not required, as the server will check for the necessary OPC UA license. If you have only the OPC UA license, you must install CygNet Bridge API, but you will not be able to use it directly. If you intend to access and use Bridge API separately for other purposes, you will need to get a separate CygNet Bridge API license. See Licensing CygNet Bridge API for more information about license types for that product.

For more information about obtaining and licensing the CygNet OPC UA and CygNet Bridge products, contact your Account Manager or CygNet Sales.