Migration freeOpcua to opcua-asyncio subscribe_data_change SubHandler method not called after subscription

[lkaupp]

Dear community,

i migrate my old freeopcua code to opcua-asyncio. Under freeopcua the following worked well (pseudo code):

class SubHandler:
    """
    Subscription Handler. To receive events from server for a subscription
    data_change and event methods are called directly from receiving thread.
    Do not do expensive, slow or network operation there. Create another
    thread if you need to do such a thing
    """
    def datachange_notification(self, node: Node, val, data):
        print(data)
 

Node.nodeid.to_string() -> save to text
read txt -> nodeid= NodeId.from_string(nodeid)
nodetosubscribe = Node(self._client.uaclient, nodeid)
handler = SubHandler()
self._opcua_subscription = self._client.create_subscription(100, handler)
self._opcua_handle = self._opcua_subscription.subscribe_data_change(nodetosubscribe)

In opcua-asyncio the code seems to working similarly (nodes will be subscribed, [function call takes different time with different amount of nodes subscribe to, equal to the amount in the freeopcua implementation]), but the datachange_notification on the Subhandler is never called. With UAExpert the changes on the same node can be monitored as usual, freeopcua implementation works as usual, but only the opcua-asyncio implementation seems to be not working. Is there something different in reinitializing the nodes from plain txt, is there more to do?

new code:

class SubHandler:
    """
    Subscription Handler. To receive events from server for a subscription
    data_change and event methods are called directly from receiving thread.
    Do not do expensive, slow or network operation there. Create another
    thread if you need to do such a thing
    """
    def datachange_notification(self, node: Node, val, data):
        print(data)
 

Node.nodeid.to_string() -> save to text
read txt -> nodeid= NodeId.from_string(nodeid)

async with self._client:
    nodetosubscribe = Node(self._client.uaclient, nodeid)
    handler = SubHandler()
    self._opcua_subscription = await self._client.create_subscription(100, handler)
    self._opcua_handle = await self._opcua_subscription.subscribe_data_change(nodetosubscribe)

[lkaupp]

Found the culprit in order to port my code from freeopcua to opcua-asyncio, the while pass loop prevented asyncio to retrieve any events. Just use: #1618 (comment)
to wait for events instead of a traditional while true pass loop.