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

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