How does the OPC-UA driver determine if it is connected?

Trying to run down a communications issue, and I came across something I wanted to clarify. I have a machine running a KEPServerEX v4 driver connected to a PLC. I also have a device set up in the OPC-UA driver connected to the same PLC. I am having some communications dropouts with this PLC that have nothing (I think) to do with the drivers, but it has brought something to light. If I have my project using the OPC-UA driver, it will occasionally disconnect then reconnect. I am also seeing this behavior in the KEPServer. However, if I delete the tag using the OPC-UA driver, it never shows disconnected.

So, now that I’ve explained all that, I’ll come to my question. Does the OPC-UA driver occasionally go out and verify the connection to the device, or once it does the initial connection, does it assume the connection is still alive until a communications error occurs?


What you are probably seeing is a read on the driver that is timing out 3 times in a row. When this happens the driver will disconnect and then reconnect.

When you delete the tag you always see the driver state as CONNECTED because there isn’t actually anything going on.

OK, that’s what I was thinking, but I wanted to make sure my observations were correct. Thanks.