OPC-UA client suddenly stops creating publish requests and eventually closes secure channel to server|OPC UA Standard|Forum|OPC Foundation

We have S7 1500 PLC’s OPC UA server communicating with a KepServerEX OPC UA client placed on a VM. There have been consistent ‘session timeouts’ issue occuring on the client. To diagnose the communication we used wireshark to monitor the traffic.

We found that usually when the communication is good, for every publish response(Server to client), there is a publish request(client to server). This does not occur in the seconds before we get a session timeout. During this time we have multiple publish responses but no publish requests. Eventually the Client sends a CloseSecureChannel request to the Server.

Another observation was that a VM read latency check was being performed at the time this issue occured. When the latency check was moved to a time when there was less traffic between OPCUA server and client, we did not see the issue reoccur.

If you have had a similar issue and have any suggestions on how to solve this or find the root cause, please let me know.

Thank you very much!