CNVString - Sending Strings from a PXI chassis over ethernet to a labWindows application on another computer

Question

I have a PXI chassis with a PXI-8101 controller. It is set up with a realtime operating system. I am communicating to it with a PC with a Windows operating system. I am trying to send variable length string messages from my PXI system to my PC.
On the PC I have a LabWindows application which can send and receive data with the PXI system. I am attempting to send error messages from the PXI system to the PC on ethernet. I am able to send numerical data between them but not the string messages. The PXI software runs to the function call CNVCreateArrayDataValue() and steps into it but never returns. It only has this problem when the parameter CNVDataType is CNVString; when I change CNVDataType to CNVBool it does not have this problem. I am new to this PXI realtime so would appreciate the help. Below is the code on my PXI system which sends these text messages.
In the beginning of RTMain I create the Writer
      CNVCreateBufferedWriter("\\\\localhost\\system\\" REG_CAL_ERROR_STRING, 0, 0, 0, 64, 5000, 0, &gErrorPublisher);
Then I call a function with a string in the parameter list:
void SendRT_ErrorMessage(char* message)
      CNVData data=0;
      int error;
      char error_str[256];
       int i;
      char out_str[ERROR_STRN_SIZE*4];
      strcpy(out_str,message);
      size_t arrayDims= ERROR_STRN_SIZE;
      arrayDims= strlen(message) +1;
      error = CNVCreateArrayDataValue(&data, CNVString, out_str, 1, &arrayDims);
      if(error<0)
            strncpy(error_str, CNVGetErrorDescription(error),256);
//    CNVPutDataInBuffer(gErrorPublisher, data, 1000);
      CNVSetArrayDataValue(data,CNVString,out_str,1,&arrayDims);
      CNVPutDataInBuffer(gErrorPublisher, data, 1000);
      CNVDisposeData(data);
Solved!
Go to Solution.

Answer 1

I've changed things around and now the application on the realtime operating system on the PXI-8101 does not hang but my host computer does not see the message correctly. It sees some characters but they are not what I sent.
I don't seem to be able to get message out of CNVData data properly. Below is the new code for the PXI-8101 controller and the Host computer LabWindows application.
Here is the code in the PXI-8101 controller now:
 CNVCreateWriter("\\\\localhost\\system\\" REG_CAL_ERROR_STRING, 0, 0, 5000, 0, &gErrorPublisher);
void SendRT_ErrorMessage(char* message)
 CNVData data=0;
 int error;
 char error_str[256];
  int i;
 char out_str[ERROR_STRN_SIZE*4];
 strcpy(out_str,message);
 size_t arrayDims= ERROR_STRN_SIZE;
 arrayDims= strlen(message) +1;
 error = CNVCreateScalarDataValue( &data,CNVString,out_str); 
 if(error<0)
  strncpy(error_str, CNVGetErrorDescription(error),256);
 CNVWrite(gErrorPublisher, data, 1000);
 CNVDisposeData(data);
And here is the code in the Host computer LabWindows application:
 sprintf(path, "\\\\%s\\system\\%s", address, REG_CAL_ERROR_STRING);
 CNVCreateSubscriber(path, ErrorMessageCallback, 0, 0, 10000, 0, &gErrorMessageSubscriber);
static void CVICALLBACK ErrorMessageCallback(void * handle, CNVData data, void * callbackData)
 char message[ERROR_STRN_SIZE];
 CNVGetScalarDataValue(data,CNVString,(void *)message);
 (void)SetCtrlVal(panelHandle,PANEL_TEXTBOX_DEBUG_MSG,"got something\n");
 (void)SetCtrlVal(panelHandle,PANEL_TEXTBOX_DEBUG_MSG,message);
 (void)SetCtrlVal(panelHandle,PANEL_TEXTBOX_DEBUG_MSG,"\n");
 CNVDisposeData(data);
You can see that I output a message "got something" so that I know I got the callback but the next line is a gibberish message "HÊl "