[SOLVED] Read Epson Printer Status using C++ and ESC/P

I'm trying to get the status of a PLQ-20 Espon printer, using C++, but with no success.

I tried that using GDI API and Escape function with PASSTHROUGH parameter, but the printer never understands the escape codes with that function.

I tried to use WIN 32 API and the example code found here. That works for sending some escape codes like BEL (to sound the buzzer) or FF (Form Feed, to eject paper from the rear of the printer), but not ESC O (to eject paper from the front of the printer), ESC 0 / ESC 1 (to initialize the printer / reset errors).

So, I tried this way to get the status of the printer with a ESC j escape code but with no success (the ReadPrinter function returns 0). Moreover, the print buffer seems to be not empty nonetheless I only send escape commands.

I don't know if I do a mistake sending escape codes or trying to read the printer status.

If anyone could post examples, it could be fine for everyone because it's hard to find them on the web.

Below is the code I use to send commands and read the result

#include <Windows.h>
#include <StdIO.h>


// **********************************************************************
// PrintError - uses printf() to display error code information
// 
// Params:
//   dwError       - the error code, usually from GetLastError()
//   lpString      - some caller-defined text to print with the error info
// 
// Returns: void
// 
void PrintError( DWORD dwError, LPCTSTR lpString )
{
#define MAX_MSG_BUF_SIZE 512
    TCHAR   *msgBuf;
    DWORD   cMsgLen;

    cMsgLen = FormatMessage( FORMAT_MESSAGE_FROM_SYSTEM |
                FORMAT_MESSAGE_ALLOCATE_BUFFER | 40, NULL, dwError,
                MAKELANGID(0, SUBLANG_ENGLISH_US), (LPTSTR) &msgBuf,
                MAX_MSG_BUF_SIZE, NULL );
    printf("%s Error [%d]:: %s\n", lpString, dwError, msgBuf );
    LocalFree( msgBuf );
#undef MAX_MSG_BUF_SIZE
}
// end PrintError
// **********************************************************************

// **********************************************************************
// ReadFileWithAlloc - allocates memory for and reads contents of a file
// 
// Params:
//   szFileName   - NULL terminated string specifying file name
//   pdwSize      - address of variable to receive file bytes size
//   ppBytes      - address of pointer which will be allocated and contain file bytes
// 
// Returns: TRUE for success, FALSE for failure.
//
// Notes: Caller is responsible for freeing the memory using GlobalFree()
// 
BOOL ReadFileWithAlloc( LPTSTR szFileName, LPDWORD pdwSize, LPBYTE *ppBytes )
{
    HANDLE      hFile;
    DWORD       dwBytes;
    BOOL        bSuccess = FALSE;

    // Validate pointer parameters
    if( ( pdwSize == NULL ) || ( ppBytes == NULL ) )
        return FALSE;
    // Open the file for reading
    hFile = CreateFile( szFileName, GENERIC_READ, 0, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL );
    if( hFile == INVALID_HANDLE_VALUE )
    {
        PrintError( GetLastError(), TEXT("CreateFile()") );
        return FALSE;
    }
    // How big is the file?
    *pdwSize = GetFileSize( hFile, NULL );
    if( *pdwSize == (DWORD)-1 )
        PrintError( GetLastError(), TEXT("GetFileSize()") );
    else
    {
        // Allocate the memory
        *ppBytes = (LPBYTE)GlobalAlloc( GPTR, *pdwSize );
        if( *ppBytes == NULL )
            PrintError( GetLastError(), TEXT("Failed to allocate memory\n") );
        else
        {
            // Read the file into the newly allocated memory
            bSuccess = ReadFile( hFile, *ppBytes, *pdwSize, &dwBytes, NULL );
            if( ! bSuccess )
                PrintError( GetLastError(), TEXT("ReadFile()") );
        }
    }
    // Clean up
    CloseHandle( hFile );
    return bSuccess;
}
// End ReadFileWithAlloc
// **********************************************************************

// **********************************************************************
// RawDataToPrinter - sends binary data directly to a printer
// 
// Params:
//   szPrinterName - NULL terminated string specifying printer name
//   lpData        - Pointer to raw data bytes
//   dwCount       - Length of lpData in bytes
// 
// Returns: TRUE for success, FALSE for failure.
// 
BOOL RawDataToPrinter( LPTSTR szPrinterName, LPBYTE lpData, DWORD dwCount )
{
    HANDLE     hPrinter;
    DOC_INFO_1 DocInfo;
    DWORD      dwJob;
    DWORD      dwBytesWritten;

    // Need a handle to the printer.
    if( ! OpenPrinter( szPrinterName, &hPrinter, NULL ) )
    {
        PrintError( GetLastError(), TEXT("OpenPrinter") );
        return FALSE;
    }

    // Fill in the structure with info about this "document."
    DocInfo.pDocName = TEXT("My Document");
    DocInfo.pOutputFile = NULL;
    DocInfo.pDatatype = TEXT("RAW");
    // Inform the spooler the document is beginning.
    if( (dwJob = StartDocPrinter( hPrinter, 1, (LPBYTE)&DocInfo )) == 0 )
    {
        PrintError( GetLastError(), TEXT("StartDocPrinter") );
        ClosePrinter( hPrinter );
        return FALSE;
    }
    // Start a page.
    if( ! StartPagePrinter( hPrinter ) )
    {
        PrintError( GetLastError(), TEXT("StartPagePrinter") );
        EndDocPrinter( hPrinter );
        ClosePrinter( hPrinter );
        return FALSE;
    }
    // Send the data to the printer.
    if( ! WritePrinter( hPrinter, lpData, dwCount, &dwBytesWritten ) )
    {
        PrintError( GetLastError(), TEXT("WritePrinter") );
        EndPagePrinter( hPrinter );
        EndDocPrinter( hPrinter );
        ClosePrinter( hPrinter );
        return FALSE;
    }

    /*********************************/
    // CODE USED TO READ THE PRINTER
    LPBYTE retData = NULL;
    LPDWORD bbr = NULL;

    if(ReadPrinter(hPrinter, retData, 1, bbr))
    {
        printf("OUT : %i", retData);
    }
    else
    {
        printf("Failed to read printer");
    }
    /*********************************/

    // End the page.
    if( ! EndPagePrinter( hPrinter ) )
    {
        PrintError( GetLastError(), TEXT("EndPagePrinter") );
        EndDocPrinter( hPrinter );
        ClosePrinter( hPrinter );
        return FALSE;
    }
    // Inform the spooler that the document is ending.
    if( ! EndDocPrinter( hPrinter ) )
    {
        PrintError( GetLastError(), TEXT("EndDocPrinter") );
        ClosePrinter( hPrinter );
        return FALSE;
    }
    // Tidy up the printer handle.
    ClosePrinter( hPrinter );
    // Check to see if correct number of bytes were written.
    if( dwBytesWritten != dwCount )
    {
        //printf( TEXT("Wrote %d bytes instead of requested %d bytes.\n"), dwBytesWritten, dwCount );
        return FALSE;
    }
    return TRUE;
}
// End RawDataToPrinter
// **********************************************************************

int main( int argc, char* argv[] )
{
    LPBYTE  pBytes = NULL;

    int textSize = 2;

    DWORD   dwSize = textSize;

    pBytes = (LPBYTE) malloc (textSize*sizeof(BYTE));

    pBytes[0] = 0x1B;
    pBytes[1] = 0x6A;


    if( ! RawDataToPrinter(L"EPSON PLQ-20 ESC/P2", pBytes, dwSize) )
        printf("Failed to send data to printer.\n" );
    else
        printf("Data sent to printer.\n" );

    free(pBytes);
    return 0;
}
// end main
// **********************************************************************

Thanks!