Question

I picked up this code from a msdn blog :

#include <windows.h> 
#include <stdio.h>
#include <conio.h>
#include <tchar.h>

#define BUFSIZE 512

int _tmain(int argc, TCHAR *argv[]) 
{ 
   HANDLE hPipe; 
   LPTSTR lpvMessage=TEXT("Default message from client."); 
   TCHAR  chBuf[BUFSIZE]; 
   BOOL   fSuccess = FALSE; 
   DWORD  cbRead, cbToWrite, cbWritten, dwMode; 
   LPTSTR lpszPipename = TEXT("H:\\Users\\uname\\Documents\\fff.txt"); 

   if( argc > 1 )
      lpvMessage = argv[1];

// Try to open a named pipe; wait for it, if necessary. 

   while (1) 
   { 
      hPipe = CreateFile( 
         lpszPipename,   // pipe name 
         GENERIC_READ |  // read and write access 
         GENERIC_WRITE, 
         0,              // no sharing 
         NULL,           // default security attributes
         OPEN_ALWAYS,  // opens existing pipe 
         0,              // default attributes 
         NULL);          // no template file 

   // Break if the pipe handle is valid. 

      if (hPipe != INVALID_HANDLE_VALUE) 
         break; 

      // Exit if an error other than ERROR_PIPE_BUSY occurs. 

      if (GetLastError() != ERROR_PIPE_BUSY) 
      {
         _tprintf( TEXT("Could not open pipe. GLE=%d\n"), GetLastError() ); 
         return -1;
      }

      // All pipe instances are busy, so wait for 20 seconds. 

      if ( ! WaitNamedPipe(lpszPipename, 20000)) 
      { 
         printf("Could not open pipe: 20 second wait timed out."); 
         return -1;
      } 
   } 

// The pipe connected; change to message-read mode. 

   dwMode = PIPE_READMODE_MESSAGE; 
   fSuccess = SetNamedPipeHandleState( 
      hPipe,    // pipe handle 
      &dwMode,  // new pipe mode 
      NULL,     // don't set maximum bytes 
      NULL);    // don't set maximum time 
   if ( ! fSuccess) 
   {
      _tprintf( TEXT("SetNamedPipeHandleState failed. GLE=%d\n"), GetLastError() ); 
      return -1;
   }

// Send a message to the pipe server. 

   cbToWrite = (lstrlen(lpvMessage)+1)*sizeof(TCHAR);
   _tprintf( TEXT("Sending %d byte message: \"%s\"\n"), cbToWrite, lpvMessage); 

   fSuccess = WriteFile( 
      hPipe,                  // pipe handle 
      lpvMessage,             // message 
      cbToWrite,              // message length 
      &cbWritten,             // bytes written 
      NULL);                  // not overlapped 

   if ( ! fSuccess) 
   {
      _tprintf( TEXT("WriteFile to pipe failed. GLE=%d\n"), GetLastError() ); 
      return -1;
   }

   printf("\nMessage sent to server, receiving reply as follows:\n");

   do 
   { 
   // Read from the pipe. 

      fSuccess = ReadFile( 
         hPipe,    // pipe handle 
         chBuf,    // buffer to receive reply 
         BUFSIZE*sizeof(TCHAR),  // size of buffer 
         &cbRead,  // number of bytes read 
         NULL);    // not overlapped 

      if ( ! fSuccess && GetLastError() != ERROR_MORE_DATA )
         break; 

      _tprintf( TEXT("\"%s\"\n"), chBuf ); 
   } while ( ! fSuccess);  // repeat loop if ERROR_MORE_DATA 

   if ( ! fSuccess)
   {
      _tprintf( TEXT("ReadFile from pipe failed. GLE=%d\n"), GetLastError() );
      return -1;
   }

   printf("\n<End of message, press ENTER to terminate connection and exit>");
   _getch();

   CloseHandle(hPipe); 

   return 0; 
}

I went through the documentation of most of the function used in the code.I didn’t find any operation that may cause trouble. Obviously opening a file inside a loop is something which shouldn’t be there. But I when compile the code ( VS 2010 Ultimate) and run it, it fails with an
ERROR_IS_SUBSTED error.
The point where GetLastError returns this error is here :

while (1) 
       { 
          hPipe = CreateFile( 
             lpszPipename,   // pipe name 
             GENERIC_READ |  // read and write access 
             GENERIC_WRITE, 
             0,              // no sharing 
             NULL,           // default security attributes
             OPEN_ALWAYS,  // opens existing pipe 
             0,              // default attributes 
             NULL);          // no template file 

I am still new to windows programming and these error codes are confusing me. The msdn documentation for this error says that An attempt was made to use a JOIN or SUBST command on a drive that has already been substituted.
So can someone from the community please

1.Clarify what is ERROR_IS_SUBSTD? The description given by msdn is too cryptic for me. 🙁

2.Why I am getting this error?

3.(somewhat off topic ) I am missing strace utility that had been my savior throughout my programming life in tracking/rectifying such errors. Do we have something similar in windows?

Answer 1

The error message looks like random nonsense unless your H drive is a network share. But even though the error message looks like random nonsense, your pipename does too.

To create a named pipe, see MSDN here:
CreateNamedPipe

The pipename has to be something like

"\\\\.\\pipe\\pipename"