C# OPC Client

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Thread Starter

Paul

Hi,

I'm looking for some easy source, how to write OPC Client on platform C#. Do you know how to get it?

Thanks.
 
Hi Paul,

I think 'easy' is a relative term. There is some work to get OPC to .NET with quality acceptable for IA applications. Some issues are; generally working with the .NET to COM interop layer, type conversions, call-backs (via COM connection points, etc.), robust error detection and reporting, support for multi-CPU and multi-core systems, event model design, watchdog monitoring, UI development, object modeling of the OPC interfaces, etc.

There are a number developer's tools available that already solve these (and more) issues for a reasonable cost to developers. A free trial and lots of examples of ours can be found at: http://IndustrialDotNet.com

Regards,

Mark
 
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Michael Batchelor

Easy is a "relative" term is correct. I wouldn't call it easy. We have developed our own in-house .net OPC client library over the past 18 months because we couldn't keep waiting for the OPC foundation to release theirs, and frankly what we've got now works far better than theirs. But at this stage of the game we probably have 2 man-years into the code base.

And getting the .net library wrapped into an AJAX control so you can ditch the HMI on the control station and just use a browser is another layer yet. In a "controlled access" network we can get updates on a fairly busy network at about the speed that an A-B Control Logix processor can service the communications requests, without an HTML page refresh BTW. (If you try to crank the OPC server's refresh rate up higher than the processor can respond to the requests things start to fall down apart.)

It really does respond well enough to use in an isolated network. But it isn't yet something that you could just hand off to a guy who isn't pretty familiar with all the nuts and bolts to start out with.

So far we haven't ever tried to use it on a public web server that's really servicing a raw IP connection where 200K people could theoretically try to look at the web page. For the life of me I can't imagine it will work well there.

I can't speak to the commercially available wrapper packages, since we never used them.

Michael
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Michael R. Batchelor
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@ Michael:

On the web page note - if you had an intermediate layer (meaning) single user for data access to the PLC - you could have as many people accessing from the web you want. The issue with the web is that you have so many users looking for their own time slice of PLC DATA - 200,000 that is 200 requests per ms and is not practical for the PLC , 1 request for a data point or thousands of data points is a much better solution using an intermediate provider layer will fix that issue for you. While the data for the web sites would not be in the web users time slice - it would be close enough.

> Easy is a "relative" term is correct. I wouldn't call it easy. We have developed
> our own in-house .net OPC client library over the past 18 months because we

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