/* Named Pipe Client */

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

VOID MyErrExit (LPTSTR lpszMessage) 
{ 
   fprintf(stderr, "%s\n", lpszMessage); 
   ExitProcess(0); 
} 

DWORD main(int argc, char *argv[]) 
{ 
   HANDLE hPipe; 
   LPVOID lpvMessage; 
   CHAR chBuf[512]; 
   BOOL fSuccess; 
   DWORD cbRead, cbWritten, dwMode; 
   LPTSTR lpszPipename = "\\\\.\\pipe\\mynamedpipe"; 
 
// 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,           // no security attributes
         OPEN_EXISTING,  // 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) 
         MyErrExit("Could not open pipe"); 
 
      // All pipe instances are busy, so wait for 20 seconds. 
 
      if (! WaitNamedPipe(lpszPipename, 20000) ) 
         MyErrExit("Could not open pipe"); 
   } 
 
// 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) 
      MyErrExit("SetNamedPipeHandleState"); 
 
// Send a message to the pipe server. 
 
   lpvMessage = (argc > 1) ? argv[1] : "default message"; 
 
   fSuccess = WriteFile( 
      hPipe,                  // pipe handle 
      lpvMessage,             // message 
      strlen((const char *)lpvMessage) + 1, // message length 
      &cbWritten,             // bytes written 
      NULL);                  // not overlapped 
   if (! fSuccess) 
      MyErrExit("WriteFile"); 
 
   do 
   { 
   // Read from the pipe. 
 
      fSuccess = ReadFile( 
         hPipe,    // pipe handle 
         chBuf,    // buffer to receive reply 
         512,      // size of buffer 
         &cbRead,  // number of bytes read 
         NULL);    // not overlapped 
 
      if (! fSuccess && GetLastError() != ERROR_MORE_DATA) 
         break; 
 
      // Reply from the pipe is written to STDOUT. 
 
      if (! WriteFile(GetStdHandle(STD_OUTPUT_HANDLE), 
         chBuf, cbRead, &cbWritten, NULL)) 
         break; 
 
   } while (! fSuccess);  // repeat loop if ERROR_MORE_DATA 
 
   CloseHandle(hPipe); 
 
   return 0; 
}