Does this support OPC XML DA?

[twiddler]

See above.

[duduyoyo]

Not supported. As a matter of fact XML DA is the least popular OPC server compared to others (DA/AE/HDA). With this solution you can parse DA return in JSON instead of XML, which is much more efficient and faster. Then you can compose SOAP message for its next destination, so why bother XML DA? Just my 2 cents. Thanks!

[twiddler]

Thank you for your answer! 🙏

I am just getting into the whole OPC topic, so I might be mistaken here. I am developing a JavaScript application which will run on a Linux machine. From what I've found out so far is that OPC DA

• uses DCOM, which I am unfamiliar with and seems to be more prominent with Windows machines, and
• requires exporting some OPC DA declaration files of some sort on the OPC DA server compared to just knowing the ItemPaths and ItemNames and putting those in a text/xml POST request.

As the machine being controlled is running quite slow, response times up to 200 ms will certainly be fine. So that's why I'm sticking with OPC XML DA.

[duduyoyo]

Looks like this solution is exactly what you're looking for,

• No DCOM, DCOM is completely out of picture and dirty work is already taken care of by this solution
• Cross platform, so you can run JavaScript in Linux to retrieve DA data from Windows server
• Slow response accepted once communication with WebSocket is established
• Full browsing path available with tag ID return in JSON, then you can put them in a text/xml POST request

Your concerns are all answered, I believe. Anything else?

[twiddler]

Thanks again for responding. :+1:

I'll check the trade-offs between

• using XML requests that leave the machine untouched and
• installing this package on the machine and using WebSockets.

[twiddler]

Right now I am super-hesitant to alter the state of the machine that I am communicating with, so I opted for node-soap and wsdl-tsclient. wsdl-tsclient gave me reasonable results that I am refining manually.

Thanks again!