Question
I am trying to list available OPC UA servers on my machine using the opcuaserverinfo command in Industrial Communication Toolbox. However, the command returns an empty value with the following warning: Warning: No OPC UA servers found.
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Expert Answer
John Williams
PhD Expert
Answered Aug 22, 2026
This could be happening due to one of the following reasons:
- The OPC UA server(s) is not registered to a Local Discovery Service (LDS) on the machine. Follow the steps here to download and install the LDS and then register your OPC UA server with the LDS.
- The OPC UA server's application instance certificate might be rejected by the LDS server. To trust the server certificate, move it from the LDS server's reject store to its trust store.The default trust and reject store of LDS are:
Reject store folder: "C:\ProgramData\OPC Foundation\UA\pki\rejected\certs"
Trust store folder: to "C:\ProgramData\OPC Foundation\UA\pki\trusted\certs"
Note: Make sure to move the file instead of copying it.
Additional Troubleshooting steps:
You could also refer to the LDS log file located in: C:\ProgramData\OPC Foundation\UA\Discovery\opcualds.log for more information. It is also possible to change the log level (and many other parameters) using the ualds.ini config file (in the same folder) to get detailed logging information.
Note: After changing LDS settings, it may be necessary to restart the LDS through the Windows “Services” console. The display name of the LDS is “OPC UA Local Discovery Server”.
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