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OPC XML-DA. Communication problem

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03 Sep 2019 05:59 #7696 by support
Hello.
Note: Both of your posts contained forward slash, no backward slash.

But anyway, I do not think there is anything to be solved on our side. Each HTTP request contains the URL used. We are sending the URL to the server precisely as it is entered into the system (e.g. what you type in Connectivity Explorer, or what you pass in the code through the QuickOPC API). You have verified that "the hard way" by finding the difference between having and not having the slash at the end, and I have verified it today by testing various URLs and observing the communication in the network analyzer.

It is the responsibility of the server to provide URLs that work, and your responsibility to use the right ones when connecting to the server. If the right ones are those with slash at the end, then you need to use them.

I do not know whether you have used the trailing slash with your dOPC Explorer tests. if you did, then it's clear. if you have not, and it still worked, then it is possible that the dOPC Explorer has added the slash by itself, but in such case it is not doing it quite right.

Best regards
The following user(s) said Thank You: Andriy

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02 Sep 2019 14:57 #7694 by Andriy
Hi,

It also works when url end up with forward slash:
http://172.17.115.68:6010/

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02 Sep 2019 12:34 #7692 by Andriy
Hi,

Sorry for the delay in replying. I've found the way how to connect to OPC XML-DA server
It works with url opc.xmlda://172.17.115.68:6010/ (backslash is required)

I have wireshark tracing file of "dOPC Connect" call, "ConnectivityExplorer TCP Connect Test" and "ConnectivityExplorer Connect" when url is valid
I haven't seen requests nor responses when url starts from 'html' or 'opc.xmlda' without trailing backslash, at least on port 6010
I can send them if you are still interested in them

Best regards
Attachments:

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29 Aug 2019 10:03 #7675 by support
Can you please send us the Wireshark capture file of the "failed" communication between Connectivity Explorer and your server (showing the original reported issues), and optionally, a Wireshark capture of a successful communication between dOPC Explorer and your server.

Thank you

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27 Aug 2019 15:09 #7664 by support
Hello.
TCP Connection Test does not send any request *inside* the TCP stream. It simply attempts to opens the socket, and the closes it if opening has succeeded.

I spoke with the developer. The current plan is that we will allow the GetStatus call be disabled also for XML-DA. We will also try to analyze what dOPC Explorer does - the hypothesis being that it does *not* call GetStatus. I will post here when I have more (allow some days).

Best regards
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27 Aug 2019 14:41 #7663 by Andriy
Hi,

You are right, the TCP Connection Test succeeded. I'm curious why Wireshark didn't trace any answer. if Connectivity Explorer sent some request I would see an answer

Best regards

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27 Aug 2019 13:15 - 27 Aug 2019 13:15 #7662 by support
Hello.

If you are referring to "TCP Connection Test" in Connectivity Explorer, then all it does is it tries to establish a TCP connection to the given host/port, and then it closes it. It does not attempt to issue any kind of request to the server. It meant to test for common error cases like "computer not running", "Server not running", "Incorrect port used", or "firewall blocks the port". I assume that the TCP Connection Test actually succeeded, is that correct? If so, any response from the server is irrelevant.

And, I apologize, it looks like that the advise I gave you (for disabling the periodic GetStatus check) was wrong. It only applies to OPC COM. The XML-DA has a different implementation which ignores this parameter. I will need to discuss with the developer what we can do to disable the GetStatus call in XML-DA. There isn't currently a setting for that. And we are not quite sure that, after doing it, things will start working.

Regarding the port choice in URL: This has been tested and should work, I do not think it is the cause.

I will post another reply here after we decide what the next step should be.

Best regards
Last edit: 27 Aug 2019 13:15 by support.
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27 Aug 2019 12:04 #7661 by Andriy
Hi,

Have you tested a case when url is configured to use another port, in my case 6010?
BTW, if you have library with internal debug logging i can try it.

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27 Aug 2019 10:31 #7660 by Andriy
Hi,

Sorry for the delay in replying. Disabling the periodic "OPC status" check does not help.
I run wireshark to analyze packets
1. When I choose "TCP Connection test" I catch response (see attached file

File Attachment:

File Name: tcp_connect_test.txt
File Size:1 KB
)
2. When I select "Refresh" - nothing. I don't see anything

I cant understand what is wrong
Attachments:

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26 Aug 2019 09:22 #7656 by support
Please try disabling the periodic GetStatus check in Connectivity Explorer like this:

1. In Connectivity Explorer, perform Tools -> Configure Connectivity.
2. Select "OPC DA Configuration ...". under Members. Select Selector -> Shared Parameters -> Client Parameters -> Server Status Check period in the right pane.
3. Enter -1 in the property grid next to "Server Status Check".
4. Press OK to close the the "Configuration Part Collection Editor" dialog.
5. Restart Connectivity Explorer (you might be asked to do so).
6. Retest.

From the code: Set EasyDAClient.SharedParameters.ClientParameters.ServerStatusCheckPeriod to Timeout.Infinite (-1), it should disable the periodic calls to GetStatus.

Note that this is a static property on EasyDAClient class, it influences connections to all servers, and it needs to be set once, before any actual instances of EasyDAClient are created.

Best regards

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