I was using opc.tcp.
I've also contacted the support via email, and given the dump and some test applications to them as well.

It's true that dump files won't solve everything, but they usually do point in the general area of where the issue is, which helps to create a reproducible situation.

Hi,

Whilst integrating OPC UA in Delphi XE3 (using the QuickOPC v5.35) I found that there's a possible deadlock.
For it to happen, I must first subscribe to one or multiple nodes. Then I restart the OPC server and whilst the OPC SDK is busy re-connecting, I try to write a value to the subscribed node. If the timing is right, a deadlock occurs.

Thinking that it was something in my program, I tested the EasyOpcUADemo.exe example (in the DemoNet folder), and it suffers from the same thing: trying to write a value to a subscribed node, at the "right" moment after a server restart, causes it to deadlock too.

This deadlock does not happen every time, so it can be a bit tricky to find the right moment where it happens. I have attached a full memory dump (with 7zip) of your demo application when it has hung.

I've been using a demo server from Unified Automation (uaserverc.exe, v1.5.1.313). To reproduce using your demo program: I start the uaserver.exe, then start your demo application, connect it to the server and subscribe to one value (e.g. Demo.Scalar.Byte). I then press 'r' in the OPC server console to make it restart, wait 3 seconds before it does so and then try to write a value. Repeat this until the deadlock occurs.

Is this a know issue? Can this be fixed?

Thanks!