OPC UA Client

OAS is both an OPC UA Client and OPC UA Server.

The Open Automation Software OPC UA Server is built into the OAS Engine which can be deployed on both Windows and Linux operating systems.  OPC UA Server support was added to OAS version 14.00.0042 and does require a license of the OPC Client Connector to enable read and write functionality.

The OPC UA Server supports browsing, reading, and writing to all local and remote OAS Tags, including Live Data Cloud, provided the OAS service hosting the Tags has a license of OPC Client.

If you want interface OAS with an OPC UA Server please see the Getting Started OPC UA Server guide.

The following guide demonstrates how to interface an OPC UA Client with OAS.

Step 1

After installing Open Automation Software verify you have a license of OPC Client on all OAS Engines that you want to interface with.  A license of OPC Client is not required on the OAS Engine where the OPC UA Server is running unless you want to communicate with the local tags on the OAS Engine.

Use the Configure OAS application and go to Configure-License and use Select to check all OAS Engines that the OPC Client product appears in the Enabled Products list.

Step 2

If security is left to the Default to Enable All Features in all OAS Engines you can proceed to Step 3.

If Security has been setup on any of the OAS Engines to restrict Tag Browsing, Reading Tags, or Writing Tags implement 1 of the 3 possible service authentication methods for the OAS OPC UA Server to gain access to the Tags.

Option 1: Go to Configure-Options-OPC and enable the property Allow OAS OPC UA Server on all OAS Engines the server will interface with.

Allow OAS OPC UA Server

Option 2: Go to Configure-Options-Remote Services and set the OPC UA Security Access to OASServiceUser and set Security User Name and Security Password to the user login that would allow Tag Browsing, Reading Tags, and Writing Tags on all OAS Engines.

OAS Service User

Option 3: Go to Configure-Options-Remote Services and set the OPC UA Security Access to OPCClientUser.  Then the OPC Client User Authentication will be set to the username and password to the user login that would allow Tag Browsing, Reading Tags, and Writing Tags on all OAS Engines.

OPC UA Client User

Step 3

In the OPC UA Client software use the endpoint url opc.tcp://localhost:58728 to connect to the server.  You can change the port number under Configure-Options-Network of the OAS Engine where the server is hosted with the property OAS OPC UA Server Port Number.

OAS OPC UA Server Port

OAS OPC UA Server Endpoint

Step 4

Connect to the server.

Note: If you are unable to connect to the OAS OPC UA Server due to a certificate security error that is shown in the OAS System Errors go to C:\ProgramData\OpenAutomationSoftware\pki-server\ on Windows or the pki-server sub-directory where the OAS Engine is located on Linux and copy the files in the rejected\certs directory to trusted\certs.

Step 5

From the OPC Client browse either the Local service or a remote service under the Network branch.

OPC UA Server Network

To add network nodes or IP Addresses where other OAS Engines are running go to Configure-Options-Networking and add to the NETWORK NODES form.  These will appear under the Network branch. 

Network Node List

We have used in this example to demonstrate the feature, but in actual use it is not needed as it would be the same as browsing Local.

You will be able to browse all Tag Groups and Tags from the local or remote OAS Engine to then see all property values available for a Tag.

Value is the most commonly used Variable.  See Tag Variables for a complete list of all variables possible.

OPC UA Tag Browse

The NodeId returned with be the full tag path and the property selected.  It this case Ramp.Value for the local Tag Ramp.


Refer to Basic Networking and Live Data Cloud Networking for how remote Tag NodeIds are returned.

Local Tag


Basic Networking


Live Data Cloud Networking from local OAS Engine


Live Data Cloud Networking though remote OAS Engine


RemotesSCADAHosting OPC UA Tag

Note: Live Data Cloud hosting is only required if the hosting server has a dynamic IP Address without a fixed IP Address or fixed network node name.  Basic Networking is the most common method of networking.

Step 7

Continue to browse additional Tag values to add to your OPC Client specifying the Publishing Rate for your desired update rate to your Client.

All Data Sources for OAS with a valid license are supported for communications through the OAS OPC UA Server.

You can deploy the OAS Engine to multiple server PCs, each OPC UA Server support communications to any OAS Engine with an OPC Client license that is also version 14.00.0042 or greater.