What is an OPC server?

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Thread Starter

Satish Salankimatt

What is an OPC server? Can anyone tell me about any website where I can get some reference material.
 
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Juan Sagasti

I´m not an authority, but I´m in the mood to write ;)

An OPC Server is a piece of software (a .exe or maybe a .dll) running in Windows and acts as a gateway between a hardware device (usually a PLC) and a generic OPC Client. The protocol between the OPC Client and the OPC Server is open, simple and adequate por typical Scada purposes.

Usually the PLC vendors offer this software for free in order to claim "our hardware can talk with any application". That´s true, but only for windows apps.

This approach (any app can talk with hardware) is killing SCADA products since their strength in the past were their "IO Servers", i.e. the messy communication layer with the hardware. Now with OPC the mess is solved by the hardware vendor, and a average VB programmer can make a scada in two hours. Score for Microsoft, again.
 
J
It's software you use instead of a device driver to communicate with devices such as PLCs, controllers, legacy DCS, as well as just about any automation equipment connected to a network. The OPC server permits OPC client software to connect and access data in the devices. OPC clients include HMI/SCADA software, auto-tuning, statistical process control, advanced control etc.

Jonas Berge
SMAR
===========
[email protected]
www.smar.com
Learn fieldbus at your own pace: www.isa.org/fieldbuses
 
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Curt Wuollet

An OPC server is a lock-in device ensuring that your automation is Windows centric and remains that way, assuring the usual fat revenue stream for the monopoly and a tax on all your users. Some folks say "It's Open, It's Open" ,but as a practical matter you _will_ have at least one Windows machine involved to make use of it. Technically you can do it elsewhere, but it's so Windows
centric that this hasn't become very popular. The idea is good enough, but the single platform makes it an impediment to opening things rather than a gateway. And it's wonderful for Microsoft, without question it's greatest beneficiary. What we need is a run anywhere scheme that does the same things without the ball and chain. Something designed from the start for automation, learning from, and correcting the infelicities of OPC would be very valuable to the community in the future.

Regards

cww
 
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Mark Hensley (Kepware)

Dear Curt,

I'm one of the folks that says it's open. At this time the OPC standard does require the use of Microsoft's COM technology for the majority of OPC applications. Like all OPC variations before it, OPC XML will become a connection option that OPC client applicaitons will adopt, it just takes time. At that point there would be no reason why an OPC Server cannot run on a platform other than windows. Now when that happens will I still plan on selling my OPC servers on these alternate platforms, YES.

Last time I checked that was called the American way. Call the me the capitalist dog that I am, but I know that my engineers, testers, technical support people and admin, all love that paycheck they get from our collective endeavour. I beleive that my customers sleep better knowing that there is a whole team of people here at Kepware working on the products, and doing so as a full time job not a side line on the weekends.
 
J
You say "but it's so Windows centric that this hasn't become very popular", do you mean to say OPC is not popular? You are correct that it is still Windows centric. But I must say that OPC is extremely popular - almost everybody wants it and demands it.

Jonas Berge
SMAR
===========
[email protected]
www.smar.com
Learn fieldbus at your own pace: www.isa.org/fieldbuses
 
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Curt Wuollet

Hi Mark

> Dear Curt,
>
> I'm one of the folks that says it's open. At this time the OPC
> standard does require the use of Microsoft's COM technology for the
> majority of OPC applications. Like all OPC variations before it, OPC
> XML will become a connection option that OPC client applicaitons will
> adopt, it just takes time. At that point there would be no reason
> why an OPC Server cannot run on a platform other than windows. Now
> when that happens will I still plan on selling my OPC servers on
> these alternate platforms, YES. <

I wish I could make things Open by declaration, it would solve a lot of problems for me. But semantics aside, even XML is now encumbered with Microsoft patents, so that's not going to be much of a solution. So even if it does eventually get sold, with appropriate commercial licenses, it will never be Open. And if I were to try to implement on a Non MS platform (which is unlikely) I would definately spend the time and money for an exhaustive patent search to give some assurance that MS couldn't render the effort a total waste. They are busy patenting their old technologies as plan B in case their unfettered monopolistic practices fail them due to disruptive technologies. All this legal IP wrangling may not affect your decisions as a "partner" but I'm fairly sure it'll
poison the well for other folks. This isn't paranoia, it's their stated purpose in obtaining these patents.

> Last time I checked that was called the American way. Call the me
> the capitalist dog that I am, but I know that my engineers, testers,
> technical support people and admin, all love that paycheck they get
> from our collective endeavour. I beleive that my customers sleep
> better knowing that there is a whole team of people here at Kepware
> working on the products, and doing so as a full time job not a side
> line on the weekends. <

Put down the paintbrush, I am a capitalist and a conservative republican and was a Cold Warrior in my own way. I'll not be painted red because I think that software agreements should resemble _all_ other contracts for goods and services with rights protected on both sides, rather than the totally one sided affairs that only monopoly power can coirce. That's not capitalism, it's totalitarianism. Cue the BSA for the jack booted thugs, and you're close to facism. Read the EULAs from an objective point of view and we'll discuss them point by point, dispassionately. You _can_ do business so it's good for both sides. That's the real revolution that's coming. Led by leftists like IBM. I doubt that anyone there has missed a paycheck.

Regards

cww
 
M
I'm one customer who paid for the Kepware OPC server because it was basically the only game in town. Yes it works, and it works very well. However, I'd much rather have an open source option so I would never be dependent upon your 'whole team of people ...' I'd be even happier if it didn't run only on MS operating systems.

Mark
 
Just in case you didn't know, COM/DCOM is also offered on WindRiver's VxWorks as well as on Microsoft Win products. See this web site for their OPC products:
http://www.t-h.de/OPC/OPCCorner_2000_10_23_d_1.htm

Dick Caro
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Richard H. Caro, CEO
CMC Associates
2 Beth Circle, Acton, MA 01720
Tel: +1.978.635.9449 Mobile: +.978.764.4728
Fax: +1.978.246.1270
E-mail: [email protected]
Web: http://www.CMC.us
Buy my book: Automation Network Selection
http://www.isa.org/rd.cfm?id=3573
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C
Hi Jonas

By "you can do it elsewhere, but it's so Windows centric that this hasn't become popular" (repetition for context), I mean that many of the underpinnings are foreign to other operating systems and you end up emulating quite a bit of Windows to implement OPC and this hasn't been very popular. That is to say, it was not written for cross platform portability.

I won't argue that it isn't popular on Windows. Black Model T Fords were very popular also, since they didn't come in any other color. Bill and Henry thought alike on this score. People will use what you give them, if they don't have any choice. Getting OS support for a "foreign" model is quite an effective barrier. Eventually (1927) Ford had to open up it's color choices to compete with other vendor's offerings. I wouldn't hold my breath waiting for Bill to open up.

Regards

cww
 
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Mark Hensley (Kepware)

Hi Dick,

Thanks for sharing that key point, yes I am aware of that as I am sure do others that use the VxWorks OS in their prodcuts. I think the problem is that like me, WindRiver expects to earn money from their efforts, and for some here on this list, there in lies the problem.
 
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Mark Hensley (Kepware)

Hi Mark,

First off, thanks for being a customer and hopefully not to reluctantly. I would love to be the only game in town but we do have our own competitors.

As a developer I can see your point but some where along the line the guy or gal that writes even an open source implmentation needs to eat. Where in the open source chain of events does anyone make money? I know you would prefer that our driver be open source, but as you may have noted, we don't charge for support, and we don't charge for upgrades. Now you may say upgrades are of little value to you once the application is done. I would argue that we are always improving our product, case in point, we are in the process of completing new work on the Siemens drivers that will improve their performance by two to three times depending on the application. No one paid us to do that, no one asked us to do that, we did it because we wanted to keep increasing the value we provide. Now since upgrades are free, anyone that has those drivers will be able to come and get them once we release them in the coming weeks.

I have many faults but please don't fault me for trying to produce the best product I can with a very dedicated group of people to help me do it.

Thanks again.
 
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Mark Hensley (Kepware)

Dear Curt,

Well my fried I see there is defintely one area that we both agree on. It won't be long and there will be nothing that is truly "Unencumbered".
 
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Michael Griffin

Re: Curt Wuollet's comments on XML

I believe that Microsoft's patents are not on XML itself, but on various means of using XML. There is a distinction to be made between the two points. While it means that using XML to interoperate with many Microsoft products can be risky for a small company without the legal resources to defend itself in court, there are many other application areas where XML can be more safely used. You are correct in that many people in the computing industry are upset with Microsoft's efforts at "poisoning the well" with respect to XML. However, this doesn't mean that all use of XML is affected.

XML is not a magic wand which makes things open or inter-operable. It is just a tool which can be used to make the task easier when the parties *want* to be open and inter-operable. The desire to be open is more important than the means used to implement it.

With regards to your suggestion that a patent search is a means of reducing software patent risk, I would suggest that you would be wasting your time with any such efforts. You don't have the time, money, or expertise to search and evaluate the patents. I would suspect that virtually any software project of any significant size (including ones we all use every day) violates at least one software patent. If you have actually read any typical software
patents, you would find that you be very hard pressed to discover just what it is that is being patented. This obfuscation is deliberate, as few patents are filed anymore to disclose and protect genuine useful inventions. Most are simply intended as cannon fodder in corporate legal battles.

Many companies have a policy that employees are *not* to conduct patent searches. The reasoning is that if you conduct a patent search, you are unlikely to discover all the patents you might infringe upon. On the other hand, you will have increased your legal liability because the assumption will be that you discovered the patent and are "wilfully" infringing upon it. My understanding is that your liability is lower if you are able to plead ignorance. This of course may vary depending upon where you live.

The above should not be construed as legal or business advice. If you need legal advice, consult a lawyer.

--

************************
Michael Griffin
London, Ont. Canada
************************
 
J
OPC is not the only way for device interface to Windows; you can use other methods as well, but most chose OPC because it is so simple and work with so many devices and applications.

OPC is an additional reason to choose Windows in automation

Jonas Berge
SMAR
===========
[email protected]
www.smar.com
Learn fieldbus at your own pace: www.isa.org/fieldbuses
 
C

Curt Wuollet

Hi Michael

On March 3, 2004, Michael Griffin wrote:
> Re: Curt Wuollet's comments on XML
>
> I believe that Microsoft's patents are not on XML itself, but on various means
> of using XML. There is a distinction to be made between the two points. While
> it means that using XML to interoperate with many Microsoft products can be
> risky for a small company without the legal resources to defend itself in
> court, there are many other application areas where XML can be more safely
> used. You are correct in that many people in the computing industry are upset
> with Microsoft's efforts at "poisoning the well" with respect to XML.
> However, this doesn't mean that all use of XML is affected. <

I believe that all use of XML is somewhat tainted by these moves. The exact legal boundaries are immaterial. Witness SCO's extention of specific disputes with IBM to all of Linux and all that has or does look, smell, or act like UNIX. With an adequate bankroll, even the most tenuous of claims can used to distroy competitors at will simply by incurring costs beyond any present or future value of the disputed IP. SCOs mistake was to take on people with the means to see the matter argued in court where hopefully, their wild claims will be disproved. How many entities could outlast Microsoft in a legal quagmire?

> XML is not a magic wand which makes things open or inter-operable. It is just
> a tool which can be used to make the task easier when the parties *want* to
> be open and inter-operable. The desire to be open is more important than the
> means used to implement it. <

Exactly, this is implicit from it's parentage. Published, so it can be paraded as somehow Open, but really accomplishing nothing towards
piercing any barriers to interoperability. It's another cut from the same cloth as OPC, where only with MS blessing or cooperation could it
open anything up. Completely within their control, business as usual. A glimmer of hope only for fools.

> With regards to your suggestion that a patent search is a means of reducing
> software patent risk, I would suggest that you would be wasting your time
> with any such efforts. You don't have the time, money, or expertise to search
> and evaluate the patents. I would suspect that virtually any software project
> of any significant size (including ones we all use every day) violates at
> least one software patent. If you have actually read any typical software
> patents, you would find that you be very hard pressed to discover just what
> it is that is being patented. This obfuscation is deliberate, as few patents
> are filed anymore to disclose and protect genuine useful inventions. Most are
> simply intended as cannon fodder in corporate legal battles. <

I left that as an exercise for the reader, whether they could ever be sure. The part that bothers me is that so many simply go ahead, knowing that as long as they play ball with MS they will be allowed to exist and perhaps even prosper. A monopoly is tied together with these little strings, no hindrance, until you try to go in the wrong direction. Then there are significant barriers to leaving. They seem invisible on the way in, just like a minnow trap. Many are already so entangled that quitting and starting over would be the only escape.

> Many companies have a policy that employees are *not* to conduct patent
> searches. The reasoning is that if you conduct a patent search, you are
> unlikely to discover all the patents you might infringe upon. On the other
> hand, you will have increased your legal liability because the assumption
> will be that you discovered the patent and are "wilfully" infringing upon it.
> My understanding is that your liability is lower if you are able to plead
> ignorance. This of course may vary depending upon where you live.
>
> The above should not be construed as legal or business advice. If you need
> legal advice, consult a lawyer. <

I think all of the above points out that the whole IP protection system needs to be scrapped and returned to it's original intent only, if
possible. Or abandoned as unworkable with practical resources. And abuse should be treated as harshly as infringement.

Perhaps a large enough body of "clean" GPL IP to choose from will render it moot.

Regards

cww
 
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Rokicki, Andrew

That and the job security of virus fighting and applying patches/upgrades. :)

The above is my personal opinion and does not necessarily reflect that of the little voices in my head

Andy R.
Somewhere at: 41 -72
 
Hi Curt,

The problem with your logic is the broad scope that many patents have been given. The idea that the use of a web server inside of a device is completely patented is like saying that I patented the use of Canvas for doing landscapes. So all you other painters better use something other than canvas if you are painting landscapes. Our patent office has made it woefully clear that they don't know the difference between the canvas and something truly unique. My point being I don't believe that there is room any more for truly clean IP. There will always be some submarine patent out there looking to extort money, with the goverment's blessing, from either vendors or customers.

For you Star Trek fans, the first episode of the Next Generation series, the Q mentioned a period in history when we kill all the lawyers. Any one feel like making history?
 
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