I've tried to review all the things you've written me and I finally understood and solved the problem. I understood the best policy would be to make the client accept the certificate, but I didn't understand how to achieve this. Then I found the certificate store folder, and it had a certificate deposited in the rejected certificate folder,I essentially cut and pasted the folders in the rejected certificate folder into the UA Applications folder, and it appears to be working correctly now. Even if it is working please let me know if there is anything mistaken in this approach.

Thank you for your assistance

Hello again,

I reread the previous messages and it seems I was a bit confused about things. You said a few messages that simply turning off the UI interaction won't solve any problem as the connection would fail, as the connection problem was a result of the trusted certificate problem.

I had not responded further because it seems I found a way to correctly set the TrustedEndpointUrls property and the problem appeared to be resolved. But at one client using our application which had been functioning correctly for six months, last week the problem suddenly represented itself. Changes were made in the system, aside from a Windows update in the PC running our easyOpcUA application. When our windows service opens our easyOpcUA application (therefore the app runs without a UI) it throws an error due to the certificate not being trusted. What is particularly strange is when the application is opened directly (therefore with the UI), the certificate confirmation dialog never appears the readings from the machine occur without errors.

In your last reply you asked if I was sure I was setting the configuration parameters before the first instance was created, I believe that is the case but I tried to refactor anyway but this made no difference.

Thank you for the support

Today I was able to try your suggestions at a client where we have the problem of the notification window. At least in this case the notification window said the problem is that self-signed certificates aren't trusted. I tried with Trusted Issuers and adding the URL to the TrustedEndpointUrls and AcceptAnyCertificate but the confirmation window appeared in any case.

It seems the best solution would be to divide our program in two programs: the current one with a user interface for testing and configuration, and a pure windows service for production. So if you could produce the documentation necessary to run our program as a Windows service without a user interface that would be greatly appreciated.

Thank you again

At the moment I am unable to read the documentation you provided about the Trusted Issue store and try to use them to implement a solution, I will do this only next week. I can clarify the points you felt were unclear however:

There are parts of your post that are not clear. Please clarify:
1. You wrote "set the property OpcLabs.EasyOpc.UA.UAEndpointDescriptor.CertificateAcceptancePolicy = true;". This makes no sense as it is not syntactically valid. Please correct.
4. Setting AcceptAnyCertificate to 'true' should work (although it's insecure). Please send me the piece of code that you have used to do it, for me to review it.

My apologies, I quickly copied this yesterday. Our program is a Windows Forms app which essentially has only a single form, and these two lines of code are called in the Form_Load event of that form:

2. I do not understand what you mean by "stays in the background". Did you want to say that it has a window, but is overlapped by other windows on the desktop? Or that it runs in a desktop-less session, so nothing is being displayed at all?
5. You wrote that "We have a program that uses your library that is launched by windows service. ". This is not fully clear. Is your program the Windows service itself? Or, is there some other Windows service that, in turn, launches your program?

As I said, the Windows service launches our program, and this service opens it in a desktop-less session, nothing is displayed.

3. If nothing is displayed by the application, how do you know that the notification window is being displayed somewhere? What are the actual symptoms?

Naturally there is no visual confirmation in this case that the window is being displayed. But if we launch our program directly it does open in the desktop we see the notification window presented. Naturally this window is not opened with all machines we use our software to communicate with, but the notification window always appears when:

• our program is opened in the desktop environment
• and attempts to communicate with specific machines (machines that were probably configured incorrectly)

Even when our program is opened in the desktop environment, if we do not give the ok to the notification window within 30 seconds, our program will not be able to communicate with the machine and it saves no data, and this is logical.

The way we confirm that the program is not functioning correctly is that our program saves nothing to the database, which it would otherwise do every few seconds. In other words, if we attempt to communicate with a machine that doesn't cause the notification window to be presented in the desktop environment the program works correctly also in a desktop-less environment. But if we communicate with a machine that does present the notification window, it does not work correctly in the desktop-less environment.

Hello,

We have a program that uses your library that is launched by windows service. Being launched by a background service, the program also stays in the background. This creates a problem when at times a dialog box is opened asking for confirmation within 30 seconds of the OPC certificate like this:


Being that program is always in the background is impossible to confirm the certificate. One solution I found here was to set the property OpcLabs.EasyOpc.UA.UAEndpointDescriptor.CertificateAcceptancePolicy = true; But this does not seem to solve the problem. I saw a similar discussion here in the forum but no final conclusion was posted if the property worked correctly or not.

Do you have an update on the matter or maybe you can tell me an alternative?

Thank you