Callback to Variable

[AndreyKl4]

Hi all!

I have faced such problem:
I have made an opcua server and added some variables. After that i connected to this server with UaExpert Client. I changed some values of variables in Client and i want to monitor changes in Server side. The question is: in what way i can observe in server side, what variables were changed? Is in python-opcua any callback function to do this?
To solve this problem i found 2 solutions:

1. To observe all variables constantly and find out differences...
2. To write the method and call it after every change of variables in Client side...
   But I think it has to be a more clever solution:)

Thanks in advance!

Andrii

[oroulet]

you can subscribe on server side. so you get a callback for every variable change

[AndreyKl4]

@oroulet Thanks for the quick answer! For subscription i have to use https://github.com/FreeOpcUa/python-opcua/blob/master/examples/client-example.py this example. Am i right? sorry for stupid questions. I am really new with opcua...

[AndreasHeine]

yes and no you need a serverside subscription!

python-opcua/opcua/server/server.py

Line 388 in 1cca33d

def create_subscription(self, period, handler):

so in difference to the client example you posted you need to call create_subscription on the server class/obj the rest is the same like in the client example

[AndreyKl4]

@AndreasHeine thanks a lot for your answer!