Algorithm 1. OPC UA Server Development Algorithm.

Input: Request messages from the OPC UA clients/middleware module.

Output: OPC UA server endpoint URI and node credentials in UA binary format.

1:  function StartOPCUAServer()

2:    Construct server endpoint URI as opc.tcp://platform IP address:port

3:    Create address space and define nine objects with associated variable nodes.

4:    Start the OPC UA server with discoverable endpoint URI.

5:    while (server.is_listening) do

6:       Call Rand() function to get periodic simulated random numbers.

7:       Update variable nodes by node.set_value(variables)

8:       Wait 1000 ms for the next iteration.

9:    end while

10:  function Listening(Request)

11:    Listen continuously for the OPC UA client requests.

12:    while (Request.available) do

13:       Parse the NodeID, value, credentials from the request.

14:       root = server.get_root_node()

15:       Objects = len(root.get_children())

16:       if (Request == “Read”) then

17:          for (i = 0; Objects; i++) do

18:             if (NodeID in root.get_children(i)) then

19:                Name = root.get_children()[i].get_browser_name()

20:                Value = root.get_children()[i].get_value()

21:                Concatenate = Name + ‘=’ + Value

22:                TagCredentials += Concatenate + ‘,’

23:             end if

24:          end for

25:          Send TagCredentials to the client

26:       elif (Request == “Write”) then

27:          for (j = 0; Objects; j++) do

28:             if (NodeID in root.get_children(j)) then

29:                Write = root.get_node(NodeID).set_value(Value)

30:             end if

31:          end for

32:       end if

33:    end while

Begin

34:  Start a thread calling StartOPCUAServer() to run the OPC UA server.

35:  Start another thread calling Listening() to handle OPC UA client requests.

Finish