Example VB6 code for Siemens OPC Client? - vb6

Question

I am trying to update an ancient VB6 project to enable communication with a remote OPC Server. I have installed the Siemens toolkit but I am unable to find any useful documentation on how to use it with VB6. (Works with C#)
The application is very simple. I just need to connect to the remote server and write/read single addresses.
I found the DatCon OCX control which I assume handles the communication but all the ServerName values I tried to enter by hand did not work.
Can anyone help?

Answer 1

Add a reference to the DLL or OCX (the seimens toolkit) to your VB6 project and then use the object browser to browse around the exposed objects. You can often times figure out what you need just be doing that.
The C# docs should also provide a wealth of info. If the library is a COM library, you'll use it essentially the same way from VB6.

Answer 2

Since posting, I did make some progress. The following example helped me to get going.
http://support.automation.siemens.com/WW/llisapi.dll?func=cslib.csinfo&objId=25229521&load=treecontent&lang=en&siteid=cseus&aktprim=0&objaction=csview&extranet=standard&viewreg=WW
Here is my current code. It's not much - just makes contact with the server and tries to write a value. I didn't get any further. I started getting COM errors and assumed the installation was bad (I had had problems installing) so I decided to reinstall. It didn't work. Installation was impossible. Waiting for an upgrade from Siemens.
'
' OPC Communication
'
' Paul Ramsden 24.11.2011
'
'
Option Explicit
Option Base 1
Public MyOpcServer As OPCServer
Public ServerHandle As Variant
Private ServerName As String
Private ServerNode As String
Private TestGroup As OPCGroup
Private MyOpcItem As OPCItem
Private IsInitialised As Boolean
Public Sub InitialiseOPC()
On Error GoTo ProcError
IsInitialised = False
Set MyOpcServer = New OPCServer
ServerNode = "xyz.abc.10.101"
ServerName = "OPC.SimaticNET.1"
Dim LocalServers
LocalServers = MyOpcServer.GetOPCServers(ServerNode)
Dim tmp
ServerHandle = ""
For Each tmp In LocalServers
If CStr(tmp) = ServerName Then
Call MyOpcServer.Connect(tmp)
MsgBox MyOpcServer.ServerNode & vbCr & MyOpcServer.ServerName & vbCr & MyOpcServer.ServerState
ServerHandle = tmp
Set TestGroup = MyOpcServer.OPCGroups.Add("TestGroup")
Exit For
End If
Next
If ServerHandle = "" Then
MsgBox "Could not find server " & ServerName & " on " & ServerNode
Else
IsInitialised = True
End If
ProcExit:
Exit Sub
ProcError:
MsgBox Err.Description
Resume ProcExit
End Sub
Private Sub ClearGroup()
Dim handles() As Long
Dim errors() As Long
Call TestGroup.OPCItems.Remove(TestGroup.OPCItems.Count, handles, errors)
End Sub
Public Sub WriteOPC(address As String, value As String)
On Error GoTo ProcError
Call ClearGroup
Set MyOpcItem = TestGroup.OPCItems.AddItem(address, 2011)
MyOpcItem.Write (value)
Exit Sub
ProcError:
MsgBox "Write error! " & Err.Description
End Sub
Public Function ReadOPC(address As String) As String
On Error GoTo ProcError
Call ClearGroup
Set MyOpcItem = TestGroup.OPCItems.AddItem(address, 2011)
Dim value As String
ReadOPC = MyOpcItem.Read
ProcError:
MsgBox "Read error! " & Err.Description
End Function
Public Sub TestOPC()
InitialiseOPC
WriteOPC "SIMATIC 300(1).CPU 315-2 DP.Q0_0TestAusgang1", "1"
End Sub