The following table lists Visual Basic global constants that can be used for client/server applications implemented to conform to the OPC specification:
'global constants for basic OPC functionality 'Variant data type definitions Public Const VT_EMPTY = 0 Public Const VT_NULL = 1 Public Const VT_I2 = 2 Public Const VT_I4 = 3 Public Const VT_R4 = 4 Public Const VT_R8 = 5 Public Const VT_CY = 6 Public Const VT_DATE = 7 Public Const VT_BSTR = 8 Public Const VT_DISPATCH = 9 Public Const VT_ERROR = 10 Public Const VT_BOOL = 11 Public Const VT_VARIANT = 12 Public Const VT_UNKNOWN = 13 Public Const VT_DECIMAL = 14 Public Const VT_I1 = 16 Public Const VT_UI1 = 17 Public Const VT_UI2 = 18 Public Const VT_UI4 = 19 Public Const VT_I8 = 20 Public Const VT_UI8 = 21 Public Const VT_INT = 22 Public Const VT_UINT = 23 Public Const VT_VOID = 24 Public Const VT_HRESULT = 25 Public Const VT_PTR = 26 Public Const VT_SAFEARRAY = 27 Public Const VT_CARRAY = 28 Public Const VT_USERDEFINED = 29 Public Const VT_LPSTR = 30 Public Const VT_LPWSTR = 31 Public Const VT_FILETIME = 64 Public Const VT_BLOB = 65 Public Const VT_STREAM = 66 Public Const VT_STORAGE = 67 Public Const VT_STREAMED_OBJECT = 68 Public Const VT_STORED_OBJECT = 69 Public Const VT_BLOB_OBJECT = 70 Public Const VT_CF = 71 Public Const VT_CLSID = 72 Public Const VT_VECTOR = &H1000 Public Const VT_ARRAY = &H2000 Public Const VT_BYREF = &H4000 Public Const VT_RESERVED = &H8000 Public Const VT_ILLEGAL = &HFFFF Public Const VT_ILLEGALMASKED = &HFFF Public Const VT_TYPEMASK = &HFFF 'OPC error code constants Public Const OPC_E_INVALIDHANDLE = &HC0040001 Public Const OPC_E_BADTYPE = &HC0040004 Public Const OPC_E_PUBLIC = &HC0040005 Public Const OPC_E_BADRIGHTS = &HC0040006 Public Const OPC_E_UNKNOWNITEMID = &HC0040007 Public Const OPC_E_INVALIDITEMID = &HC0040008 Public Const OPC_E_INVALIDFILTER = &HC0040009 Public Const OPC_E_UNKNOWNPATH = &HC004000A Public Const OPC_E_RANGE = &HC004000B Public Const OPC_E_DUPLICATE_NAME = &HC004000C Public Const OPC_E_INVALIDCONFIGFILE = &HC0040010 Public Const OPC_E_NOTFOUND = &HC0040011 Public Const OPC_E_INVALID_PID = &HC0040203 Public Const OPC_S_UNSUPPORTEDRATE = &H4000D Public Const OPC_S_CLAMP = &H4000E Public Const OPC_S_INUSE = &H4000F Public Const OPC_E_NOTCOMMUNICATING = &HC0040800 Public Const OPC_S_NOTCOMMUNICATING_ITEMADDED = &H40801 Public Const OPC_E_FB_MODE_ERROR = &HC0040802 Public Const OPC_E_DATABASE_NOT_OPENED = &HC0040803 Public Const OPC_E_NO_BRANCHES_TO_BROWSE_DOWN = &HC0040804 Public Const OPC_E_NOT_A_VALID_BRANCH = &HC0040805 Public Const OPC_E_NOT_WRITEABLE = &HC0040806 Public Const OPC_E_REVISION_MISMATCH = &HC0040807 Public Const DV_E_INVALIDDEVICENAME = &HC0040808 Public Const DV_E_INVALIDDEVICEID = &HC0040809 Public Const DV_E_INVALIDDEVICEOBJECT = &HC004080A Public Const DV_E_LICENSE_EXCEEDED = &HC004080B Public Const DV_S_NOCONNECTEDDEVICES = &H4080C