OPC学习（二）

某些OPC Server有一些自定接口，需要查看其文档才能正确使用其功能。如KEBA的控制器：“Kemro.opc.4.IF1.1.88“，在创建COM对象获得了IOPCServer接口后，需要再查询一个IKebaOpcConfig接口，然后调用其AddSystem函数添加一台设备：

vServerIntf := CreateComObject(ProgIDToClassID(TOPCServerInfo(ANode.Data).ProgID)) as IOPCServer; if vServerIntf = nil then begin Application.MessageBox(PChar(S_FailedConnectOPCServer),PChar(Application.Title),mb_IconError or mb_OK); Exit; end; vServerIntf._AddRef; ANode.Values[Column_Instance.ItemIndex]:=Integer(vServerIntf); ANode.Values[Column_Status.ItemIndex]:=nsActive; if GUIDToString(ProgIDToClassID(TOPCServerInfo(ANode.Data).ProgID))='{B7AF0914-D2C8-4A3B-9939-E607A5509C9F}' then begin vServerIntf.QueryInterface(IKebaOpcConfig,vConfigIntf); if vConfigIntf<>nil then vConfigIntf.AddSystem(PWideChar(WideString('192.168.181.176')),PWideChar(WideString('192.168.181.176'))); end;

这个方法与通过opcsvc.ini来配置设备有差别，只有通过IKebaOpcConfig添加的设备，在展开Item时，才能看到SVs下的资料。

有个朋友使用VB.Net开发OPC Client，出现不稳定的状况，有时正确有时错误：

Private Sub test() Try proxyIKebaOpcConfig.AddSystem("192.168.181.176","192.168.181.176") Catch ex As Exception proxyIKebaOpcConfig.RemoveSystem("192.168.181.176") MsgBox("error") End Try Dim item As New OPCITEMDEFintern() item.hClient = 2 item.szAccessPath = "" item.szItemID = "192.168.181.176.SVs.system.sv_MoldFwdVis.Points[1].press" 'item.szItemID = "192.168.27.66.SVs.system.do_MotorOff" item.vtRequestedDataType = VarEnum.VT_EMPTY ',Int16) 'VarEnum 这个枚举要好好研究一下； item.pBlob = Nothing item.bActive = True item.dwBlobSize = 0 item.wReserved = 0 Dim count As Int16 = 1 Dim nSize As Int32 = Marshal.SizeOf(item) 'GetType(OPCITEMDEFintern)) Dim ptrDef As IntPtr = Marshal.AllocCoTaskMem(nSize) Marshal.StructureToPtr(item,ptrDef,True) 'item = Nothing 'GC.Collect() Dim ptrRes As IntPtr Dim ptrErr As IntPtr Dim hresult As Int32 Dim hServer(0) As Int32 Dim ptrItemValues As IntPtr Dim ptrItemErrs As IntPtr = IntPtr.Zero Dim timestamp As Int64 Dim quality As Int32 Dim datavalue As Int32 Dim err As Int32 hresult = proxyIOPCItemMgt.AddItems(count,ptrRes,ptrErr) Dim erro As Int32 = Marshal.ReadInt32(ptrErr) 'Marshal.FreeCoTaskMem(ptrErr) Dim ptrCancleID As Int32 = 0 Dim ptrTransactionID(0) As Int32 ptrTransactionID(0) = 1 If hresult = 0 Then Thread.CurrentThread.Sleep(1000) For i = 0 To count - 1 hServer(0) = Marshal.ReadInt32(ptrRes) For j = 0 To 100 ptrItemValues = IntPtr.Zero ptrItemErrs = IntPtr.Zero hresult = proxyIOPCSyncIO.Read(OPCDATASOURCE.OPC_DS_DEVICE,1,hServer,ptrItemValues,ptrItemErrs) ptrTransactionID(0) += 1 Dim er As Int32 = Marshal.ReadInt32(ptrItemErrs)

查来查去，发现Marshal.StructureToPtr(item,True)的第3个参数传False就比较正常，但原因不明。

（编辑：李大同）

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