OPC UA Connection To Top Server Reset

We have a Gateway with an OPC-UA connection to a Top Server IO Server which generally works fine.

However, the Top-Server is polling PLC’s over VPN connections to several sites. Periodically (say 7-14 days) for various reasons the VPNs go offline, and some time later re-establish themselves. At this point for some reason the OPC-UA connection between the Gateway and Top Server stays ‘bad’, such that communication to the PLC’s is not re-established.

The Gateway Log is full of various errors from the time the VPNs drop off such as:

UaTCPClientSymmetricHandler: Error decoding Symmetric Message
UaTCPClientSymmetricHandler: No UARequestFuture for RequestID xxxxx
Active: Channel went Inactive (GatewayIPAddr:port -> TopserverIPAddr:port)

These type of errors recur in the logs, even after the VPNs are re-established.

To correct this, if I disable, and then re-enable the OPC Connection in the Gateway Config, all is immediately well. For some reason it appears the OPC connection itself is degraded during this process - the Gateway Server and Top Server are both on a local network and are not affected when the external VPNs go down - they can still see each other fine and the OPC connection itself is reported as ‘connected’ in the Gateway.

We have PLC heartbeat alarms generated to notify us when comms goes down to each PLC, so I am wondering if there is any way I can automate refreshing the OPC connection? I cannot see any scripting functions for this, and the Gateway OPC Enabled tags appear to be read-only.

Gateway is 7.8.0, Top Server version is 5.19.

Any help appreciated.


There were a bunch of OPC-UA issues fixed for 7.8.1, including what you’re seeing. Give that a shot and let us know.

Thanks for the very rapid response.

I will let you know once we have a result.


Did upgrading to 7.8.1 fix your problem?

I’m having a very similar, intermittent problem with an Ignition 7.8.0 OPC-UA connection to KepServer. The connection just stops responding and the tags and overlays go to the STALE (but not the BAD) condition. The connection appears in the Quick Client page on the gateway, but I’m unable to browse to it. The log has tons of lines like:

8:23:21 AM UaTcpClientSymmetricHandler No UaRequestFuture for requestId=6
8:23:21 AM UaTcpClientSymmetricHandler No UaRequestFuture for requestId=16
8:23:21 AM UaTcpClientSymmetricHandler No UaRequestFuture for requestId=15

The only solution I’ve found is to disable and reenable the connection to KepServer.



“Top Server” is Kepware’s “KEPServerEX” licensed to “Software Toolbox”, they are the same product and consequently will act in the same way.