CVT Client Communication (CCC)

[praveen91]

Hi

I am facing a issue with CCC, I could able to write and read dbl str and boolean but sgl pt values were not getting updated in CCC. CVT is not shoeing any error while writing and CCC while reading but I am getting default value.

suggest me solution to write and read sgl pt using CVT-CCC.

Thanks in advance.

[praveen91]

Hi

I want to write tag in one place (RT) and read the value in two different running vi on two different system.

please share your suggestions.

Thanks in advance....

[xl600]

I'd like to make a change to https://github.com/NISystemsEngineering/CVTClientCommunication/issues but I don't know what VIPM version this is aligned to.  The GITHub repo isn't tagged and LVCompare is all but useless to compare VIs in-bulk, in libraries, or VIs with vi.lib dependencies where the vi.lib dependencies are part of the differences (I wish LabView offered an XML based VI rather than binary!).

Hope it's 3.0.3.9, which is shown to be the latest in VIPM.

Thanks,

XL600

[xl600]

Answered it for myself.  There's a ".vipb" build spec in the GIT sources which show the 'next version' to be 3.0.3.10, thus the current version is 3.0.3.9.

[Noriker]

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@praveen91 wrote:

Hi

I am facing a issue with CCC, I could able to write and read dbl str and boolean but sgl pt values were not getting updated in CCC. CVT is not shoeing any error while writing and CCC while reading but I am getting default value.

suggest me solution to write and read sgl pt using CVT-CCC.

Thanks in advance.

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Hi, we seem to have a similar problem. Have your problem of getting default value resolved? 

We have problems using CCC between two remote RT targets connected through satellite Ethernet link. We are only sending small volumes of data, and are setting the client loop rate to be 5000ms but the high latency (1.5s) seems to cause some of the CVT variables to often have 0 value. This is something we don't understand. If the communication were interrupted, the CVT variables should maintain their value. Also it is common that some of the variables are transmitted correctly in an individual transmission, but others are not. Note that we modified the timeout in the CCC connection to accommodate the latency.

Can anyone help please? Thanks.

[Noriker]

Hi, hope this discussion thread is still live.

We have problems using CCC between two remote RT targets connected through satellite Ethernet link. We are only sending small volumes of data, and are setting the client loop rate to be 5000ms but the high latency (1.5s) seems to cause some of the CVT variables to often have 0 value. This is something we don't understand. If the communication were interrupted, the CVT variables should maintain their value. Also it is common that some of the variables are transmitted correctly in an individual transmission, but others are not. Note that we modified the timeout in the CCC connection to accommodate the latency.

The strange thing is the program works perfectly when both CCC server and client at the same location, ie. the problem occurs only when the CCC server and Client were connected remotely.

Please see the images.

Can anyone help to explain please? Many thanks.

[BeCeGa]

Hi Noriker

   The tread is still alive, but CCC is a library we are not actively developing. In general for new designs we recommend using DCAF (Distributed Control and Automation Framework more information in ni.com/dcaf). 

 Have you change the values for timeouts? Are you seeing any error in other parts of your code? They way you have your error code wired, you might not be able to see if error happens.  If there is an error, it wont be seen until the loop ends, but they are not persistent, so when it ends the error might be gone.

 What side is getting the tag with the 0 value, the client or the server?

 Have you tried using the CCC example in this setting to see if you get a similar behavior?

 When you see the problem does it happens to all tags or just some tags?

Best Regards

[Noriker]

Hi Benjamin,

Sorry if I haven't replied. Have been working on the other things. To answer your questions:

Have you change the values for timeouts?

Yes.

Are you seeing any error in other parts of your code?

No.

What side is getting the tag with the 0 value, the client or the server?

Server side

 Have you tried using the CCC example in this setting to see if you get a similar behavior?

Yes.

When you see the problem does it happens to all tags or just some tags?

Just some tags.

In addition, a bug is discovered in NI_CCC.lvlib:Stop Server.vi: the port number is not wire to FG Server Instances.vi. See attached. The first case it should be wired, the second case has no need.

Should I change it?

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[xl600]

Long ago, I checked in a change which fixed bugs and added per connection IDs to enable multiple servers and much more reliable reconnections.  Feel free to pull it from the CCC github branch.  It hasn't been merged into the mainline (I don't think anyone is maintaining CCC anymore).

https://github.com/xl600/CVTClientCommunication/commit/0139d8d5803a55303f2d74112476361169f99eae

Edit: This does not fix the bug in Stop Server.vi mentioned.  I never use the port specific stop server (I always use the stop all option).

[Noriker]

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@xl600 wrote:

Long ago, I checked in a change which fixed bugs and added per connection IDs to enable multiple servers and much more reliable reconnections.  Feel free to pull it from the CCC github branch.  It hasn't been merged into the mainline (I don't think anyone is maintaining CCC anymore).

https://github.com/xl600/CVTClientCommunication/commit/0139d8d5803a55303f2d74112476361169f99eae

Edit: This does not fix the bug in Stop Server.vi mentioned.  I never use the port specific stop server (I always use the stop all option).

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Thanks very much for the comments. If CCC library is not current anymore, what is the alternative?

Do you have a strategy to deal with network disconnection, such as unplug the ethernet cable? We can reestablish CCC connection after network cable disconnected, but it takes two minutes to do so. Do you have a better way?  Thanks.