Connection to server OPC NI

Question

Hello,
I need help, I try to connect a software developped with LabWinows/CVI 9.0 to the opc server of National Instrument.
The tag is "opc://localhost/National Instruments.Variable Engine.1//./QGAPro/5_2" or "opc://localhost/National Instruments.Variable Engine.1//./QGAPro/5_4" for example.
But the program returns "Error: Can't add item to OPC Group. The item ID is not defined in the server address space or no longer exists in the server address space."
I can check the tag with client opc like :
How can I know where is the problem please?
Do you know where is the problem?
Thank you.
Bye. Karine.

Answer 1

You can find below a piece of code.
I can connect to the server OPC with a client test, but I can't in my program.
char opc_target[] = { "opc://localhost/National Instruments.Variable Engine.1//./QGAPro/            " };
static DSEnum_Status status_inline = DSConst_Unconnected;
static DSHandle dsHandle[512] = { 0 };
static void ShowDataSocketError(HRESULT errorCode);
/* This is the callback function for the DataSocket */
void CVICALLBACK DSCallback (DSHandle dsHandle, int event, void *callbackData);
void fieldbus_init(void)
    HRESULT hr = S_OK;
                char chaine_temp[50];
                int i, j;
                opc_target[65] = '\0';
                strcat(opc_target, "5_2");
    hr = DS_Open (opc_target, DSConst_ReadAutoUpdate, DSCallback, NULL, &dsHandle[0]);                  //=> hr : « Opération réussie »
void DSCallback (DSHandle localDSHandle, int event, void *pUserData)
    HRESULT hr = S_OK;
    char message[1000];
    switch (event) {
        case DS_EVENT_DATAUPDATED:
            break;
        case DS_EVENT_STATUSUPDATED:
            DS_GetStatus (localDSHandle, &status_inline);
            hr = DS_GetLastMessage (localDSHandle, message, 1000);                                                              //=> message : « Can't add item to OPC Group.  The item ID is not defined in the server address space or no longer exists in the server address space. »
            break;
    return;
I can't modify tags because this is another software that generates and which is developed by another company.
I have to read these tags to retrieve the associated values (values of a gas analyzer).
Can you help me with these informations please?
Thank you!
Karine