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import asyncio |
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import logging |
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from asyncua import Client, ua |
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from asyncua.common.events import Event, get_filter_from_event_type |
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logging.basicConfig(level=logging.INFO) |
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_logger = logging.getLogger(__name__) |
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class SubHandler: |
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def __init__(self): |
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self.currentConditions = {} |
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""" |
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Subscription Handler. To receive events from server for a subscription |
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data_change and event methods are called directly from receiving thread. |
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Do not do expensive, slow or network operatsion there. Create another |
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thread if you need to do such a thing |
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""" |
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def event_notification(self, event): |
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_logger.info("New event received: %r", event) |
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# To avoid special event for ConditionRefresh 'Condition refresh started for subscription X.' |
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if (event.NodeId): |
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conditionId = event.NodeId.to_string() |
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conditionKeys = self.currentConditions.keys() |
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# A alarm/condition appears with Retain=True and disappears with Retain=False |
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if event.Retain and not conditionId in conditionKeys: |
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self.currentConditions[conditionId] = event |
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if not event.Retain and conditionId in conditionKeys: |
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del self.currentConditions[conditionId] |
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_logger.info("Current alarms/conditions: %r", conditionKeys) |
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async def main(): |
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# OPCFoundation/UA-.NETStandard-Samples Quickstart AlarmConditionServer |
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url = "opc.tcp://localhost:62544/Quickstarts/AlarmConditionServer" |
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async with Client(url=url) as client: |
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alarmConditionType = await client.nodes.root.get_child(["0:Types", "0:EventTypes", "0:BaseEventType", "0:ConditionType", |
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"0:AcknowledgeableConditionType", "0:AlarmConditionType"]) |
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conditionType = await client.nodes.root.get_child(["0:Types", "0:EventTypes", "0:BaseEventType", "0:ConditionType"]) |
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# Create Operand for necessary field ConditionId |
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# Hint: The ConditionId is not a property of the event, but it's NodeId. |
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# ConditionId is named "NodeId" in event field list. |
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conditionIdOperand = ua.SimpleAttributeOperand() |
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conditionIdOperand.TypeDefinitionId = ua.NodeId(ua.ObjectIds.ConditionType) |
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conditionIdOperand.AttributeId = ua.AttributeIds.NodeId |
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# Add ConditionId to select filter |
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evfilter = await get_filter_from_event_type([alarmConditionType]) |
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evfilter.SelectClauses.append(conditionIdOperand) |
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# Create subscription for AlarmConditionType |
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msclt = SubHandler() |
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sub = await client.create_subscription(0, msclt) |
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handle = await sub.subscribe_events(client.nodes.server, alarmConditionType, evfilter) |
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# Call ConditionRefresh to get the current conditions with retain = true |
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# Should also be called after reconnects |
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await conditionType.call_method("0:ConditionRefresh", ua.Variant(sub.subscription_id, ua.VariantType.UInt32)) |
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await asyncio.sleep(30) |
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await sub.unsubscribe(handle) |
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if __name__ == "__main__": |
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asyncio.run(main()) |
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FreeOpcUa /
opcua-asyncio
