Python-opcua编程 (2) 通过路径获取节点、事件

例（1）通过路径获取

使用 get_children()和get_child(path) 两个函数。服务器和客户端都适合.

客户端

import sys
sys.path.insert(0, "..")
from opcua import Client

if __name__ == "__main__":
    client = Client("opc.tcp://localhost:4840/freeopcua/server/")
    #connect using a user
    # client = Client("opc.tcp://admin@localhost:4840/freeopcua/server/")
    try:
        client.connect()

        # Client has a few methods to get proxy to UA nodes that
        #  should always be in address space such as Root or Objects
        root = client.get_root_node()
        print("Objects node is: ", root)

        # Node objects have methods to read and write node attributes
        #  as well as browse or populate address space
        print("Children of root are: ", root.get_children())

        # get a specific node knowing its node id
        #var = client.get_node(ua.NodeId(1002, 2))
        #var = client.get_node("ns=3;i=2002")
        #print(var)
        #var.get_data_value() # get value of node as a DataValue object
        #var.get_value() # get value of node as a python builtin
        #var.set_value(3.9) # set node value using implicit data type

        # Now getting a variable node using its browse path
        myvar = root.get_child(["0:Objects", "2:MyObject", "2:MyVariable"])
        obj = root.get_child(["0:Objects", "2:MyObject"])
        print("myvar is: ", myvar)
        print("myobj is: ", obj)
        print(myvar.get_value())

    finally:
        client.disconnect()

服务器端的路径读取

import sys
sys.path.insert(0, "..")
import time
from IPython import embed


from opcua import ua, Server, instantiate


if __name__ == "__main__":

    # setup our server
    server = Server()
    server.set_endpoint("opc.tcp://0.0.0.0:4840/freeopcua/server/")

    # setup our own namespace, not really necessary but should as spec
    uri = "http://examples.freeopcua.github.io"
    idx = server.register_namespace(uri)

    # create our custom object type
    dev = server.nodes.base_object_type.add_object_type(0, "MyDevice")
    dev.add_variable(0, "sensor1", 1.0)
    dev.add_property(0, "device_id", "0340")
    ctrl = dev.add_object(0, "controller")
    ctrl.add_property(0, "state", "Idle")

    # instantiate our new object type
    mydevice = instantiate(server.nodes.objects, dev, bname="2:Device0001")
    #mydevice = server.nodes.objects.add_object(2, "Device0001", objecttype=dev)  # specificying objecttype to add_object also instanciate a node type
    mydevice_var = mydevice.get_child(["0:controller", "0:state"])  # get proxy to our device state variable 

    # starting!
    server.start()

    try:
        mydevice_var.set_value("Running")
        embed()
    finally:
        # close connection, remove subcsriptions, etc
        server.stop()

mydevice_var = mydevice.get_child(["0:controller", "0:state"]) 

例-2 服务器产生事件

import sys
sys.path.insert(0, "..")

from opcua import ua, Server


if __name__ == "__main__":
  

    # setup our server
    server = Server()
    server.set_endpoint("opc.tcp://localhost:48400/freeopcua/server/")

    # setup our own namespace, not really necessary but should as spec
    uri = "http://examples.freeopcua.github.io"
    idx = server.register_namespace(uri)

    # get Objects node, this is where we should put our custom stuff
    objects = server.get_objects_node()

    # populating our address space
    myobj = objects.add_object(idx, "MyObject")

    # Creating a custom event: Approach 1
    # The custom event object automatically will have members from its parent (BaseEventType)
    etype = server.create_custom_event_type(idx, 'MyFirstEvent', ua.ObjectIds.BaseEventType, [('MyNumericProperty', ua.VariantType.Float), ('MyStringProperty', ua.VariantType.String)])

    myevgen = server.get_event_generator(etype, myobj)

    # Creating a custom event: Approach 2
    custom_etype = server.nodes.base_event_type.add_object_type(2, 'MySecondEvent')
    custom_etype.add_property(2, 'MyIntProperty', ua.Variant(0, ua.VariantType.Int32))
    custom_etype.add_property(2, 'MyBoolProperty', ua.Variant(True, ua.VariantType.Boolean))

    mysecondevgen = server.get_event_generator(custom_etype, myobj)

    # starting!
    server.start()

    try:
        # time.sleep is here just because we want to see events in UaExpert
        import time
        count = 0
        while True:
            time.sleep(5)
            myevgen.event.Message = ua.LocalizedText("MyFirstEvent %d" % count)
            myevgen.event.Severity = count
            myevgen.event.MyNumericProperty = count
            myevgen.event.MyStringProperty = "Property " + str(count)
            myevgen.trigger()
            mysecondevgen.trigger(message="MySecondEvent %d" % count)
            count += 1

        embed()
    finally:
        # close connection, remove subcsriptions, etc
        server.stop()

可以通过uaExpert EventView 看到事件 。但是不知道如何查看secondEvent的Property