added usage example

Author: brubbel

examples/server-persistent.py

@@ -0,0 +1,49 @@
+import sys
+sys.path.insert(0, "..")
+import time
+import random
+
+from opcua import Server
+from opcua.common.sqlite3_backend import SQLite3Backend
+from opcua.server.address_space_sqlite import StandardAddressSpaceSQLite, AddressSpaceSQLite
+
+ITEMS = ('Pump', 'Motor', 'Fan', 'Gearbox', 'Filter', 'Building', 'Ventilation')
+
+if __name__ == "__main__":
+
+    print('\nStart and stop this server multiple times and\n'
+          'verify that address space is persisted in SQL.\n'
+          'Values written from any opc-ua client into the\n'
+          'server are also stored.\n')
+
+    with SQLite3Backend(sqlFile='my_address_space.py', readonly=False) as backend, \
+         StandardAddressSpaceSQLite() as stdAspace, \
+         AddressSpaceSQLite(backend=backend, cache=stdAspace) as myAspace:
+
+        # setup our server
+        server = Server(aspace=myAspace)
+        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)
+    
+        # get Objects node, this is where we should put our nodes
+        objects = server.get_objects_node()
+    
+        # populating our address space
+        myobj = objects.add_object(idx, "{:s}-{:d}".format(random.choice(ITEMS), random.randint(1,100)))
+        myvar = myobj.add_variable(idx, "MyVariable", 42)
+        myvar.set_writable()    # Set MyVariable to be writable by clients
+    
+        # starting!
+        server.start()
+        
+        try:
+            while True:
+                time.sleep(1)
+        except KeyboardInterrupt:
+            pass
+        finally:
+            #close connection, remove subcsriptions, etc
+            server.stop()