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Remote Operator, URC files and slow connections


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I launch Remote Operator as a Remote Application, i.e. an rdp Application as opposed to and rdp DeskTop. This is used by clients to access remote PLC via a 3G WAN.


It all works well except for the effect of a slow speed network.


I do set UR2 file to VNC Mode and I do have URC files in a cache directory. HMI >> Mouse>> to button Press is very fast but update of screen is VERY slow.


I would like to know;

  • How does Remote Operator choose correct URC for a particular site? They are all in a common directory however there does not appear to be a setting in the ur2 file to point to the urc.
  • Is there any way of improving the slow response?


Network Speed is typically 3 to 7 Mbps

User.config is edited to point to a User Drive for ur2 files and set vnc mode however I cannot find a pointer for urc files.




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When you import a URC file, Remote Operator registers it with CRCs to match Images and Fonts. When you connect to the PLC, it tries to find a urc file with a matching CRCs.



Slow response also happens because of the number of variables in the screen, and also the latency of the network (ping time). This is why in LAN, you would get the most of the speed.


Certain improvements have been made in the last version in order to improve the speed of remote operator.


The slowest part is when switching from one screen to another (because Remote Operator needs to question the PLC about the new screen), and we might improve that in the future by also providing an application cache

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  • 3 weeks later...

Thank you...

That makes sense.

By CRC, I assume you mean Circular Redundancy Check, so any file changes or even program changes would potentially affect the CRC generated?


This also implies that a URC file is particular to a PLC and a site and that any URC created for a PLC cannot be simply copied, the file must be created from the PLC directly? ( I do not copy URC files, just checking).


Also, where are the CRC's stored so that I can make certain that I am not "polluting" any previous image with any potential data store moves, adds and changes?


If I update the application does the existing data, (CRC's) get updated?


I have multiple clients each with multiple PLC's that I administer.


If a single client has multiple sites then there are a larger number of URC files to be searched for a matching URC, eg if the client has 16 sites then there will be 16 URC files in the common profile directory to search for a match each time a screen changes. I will try to think of a way to re order the data store to reduce this.


Unfortunately my network is 3G based and latency can be from 20mS to 1200mS, typically 250mS.


Any updates to the efficiency of Remote Operator would be greatly appreciated.





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Any change to fonts or Images will affect the CRCs. The CRCs are calculated on the sum of all fonts and the sum of all images.

The URC is per program (not PLC), so a URC that matches a specific program can be used for the same program running on a different PLC.


The CRCs are stored in a file called Cache.xml

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  • 1 month later...

Hi Saragani...

Thanks for the update, I appreciate the feedback.


It would be GREAT if you did do some work for increasing the efficiency of the screen update, this application works VERY well for us, we have 5 companies over 19 sites monitoring and controlling Waste Water plants remotely on a daily basis.




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