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Unable to update tag address in Kepware while my service using OPCLabs

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23 Mar 2015 10:01 #2983 by support
I cannot know for sure what the Kepware message "Active connections still exist." refers to, but you are right, it probably refers to an reference to an OPCServer object (in OPC Classic) or an OPC UA Session, which are "global" connections, not to a tag. The other (less likely) explanation is that it refers to an OPCItem (in OPC Classic), or an OPC UA monitored item.

If you subscribe (I guess that's what you call "listen to") an item/monitored item ("tag"), our software will attempt to remain connected until you explicitly unsubscribe using one of ther UnsubscribeXXXX methods.

If you do one-time operations such as ReadXXXX, WriteXXXX, we will connect and then remain connected for a "hold period", then disconnect unless there is another request or a subscription (see above).

Therefore if you are no longer calling operations such as OPC reads and writes, AND you have explicitly unsubscribed from the subscriptions you have made, you should see that after the hold period elapses, our client (you application) disconnects from the target OPC server.

If this is not what you observe, pls provide a way to reproduce the issue.

The default hold periods differ between OPC Classic and OPC UA and depend on the operation(s) performed, but do not exceed 60 seconds total in version 5.32. Earlier versions might have somewhat different defaults.

Best regards

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23 Mar 2015 07:15 #2978 by adid@contel.co.il
hello,

my service using opcLabs is listening to 4 tags.
after running the service, and it's began listen to the 4 tags, after i get event change in one tag i am going to read a list of tags ( where none of them is the tag we listen ) - for example i am going to read tag ExtruderOn. than if i try to change the Kepware tag ExtruderOn ( after finish reading it with opcLabs ) i get the error : "Active connections still exist."
so my question is if i must stop my service in order to change the tag ExtruderOn ?
and if the connection is still open, than the connection is to the Kepware and not for specific tag. correct ?

thank you,
Adi Damty

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21 Mar 2015 17:17 #2963 by support
You did not describe at which moment you get the " Active connections still exist."

Anyway, QuickOPC makes OPC appear connection-less to the developer, but OPC is connection-based nevertheless. If you do not subscribe to any item, we open the connection if needed, perform the operation, and then keep it open for a configurable "hold period". Isn't this the explanation?
The following user(s) said Thank You: adid@contel.co.il

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18 Mar 2015 15:08 #2961 by adid@contel.co.il
hello,

i try to update tag address in Kepware ( type BCD ) while my service that using OPCLabs is running.
than i get an error in Kepware : Active connections still exist.
when i stop my service than i succeed to change the tag address.
i didn't listen to any changes in this tag, than i don't understand why i am getting this error.

thank you,
Adi Damty

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