Raw printing directly to a USB printer, bypassing Windows spooler

Question

I\'m experimenting with a Zebra TTP8200 thermal printer. For my application I need to print plotter type traces continuously until the user hits a stop button. I\'ve had a p

Answer 1

The below class in C# is something I've adapted from a Microsoft Knowledgebase article. There are methods in this class to send the print job as a string and byte[]. Please note there are some references to log4net in there that can be removed/replaced with the logging framework of your choice. :

/// 

/// Class used to aid in sending raw printer data (PS, PRN, etc) directly to the printer.
/// This class was taken from http://support.microsoft.com/kb/322091
/// 
public class PrintQueueUtility
{
    private static ILog log = LogManager.GetLogger(typeof(PrintQueueUtility));

    [DllImport("winspool.Drv", EntryPoint = "OpenPrinterA", SetLastError = true, CharSet = CharSet.Ansi, ExactSpelling = true, CallingConvention = CallingConvention.StdCall)]
    public static extern bool OpenPrinter([MarshalAs(UnmanagedType.LPStr)] string szPrinter, out IntPtr hPrinter, IntPtr pd);

    [DllImport("winspool.Drv", EntryPoint = "ClosePrinter", SetLastError = true, ExactSpelling = true, CallingConvention = CallingConvention.StdCall)]
    public static extern bool ClosePrinter(IntPtr hPrinter);

    [DllImport("winspool.Drv", EntryPoint = "StartDocPrinterA", SetLastError = true, CharSet = CharSet.Ansi, ExactSpelling = true, CallingConvention = CallingConvention.StdCall)]
    public static extern bool StartDocPrinter(IntPtr hPrinter, Int32 level, [In, MarshalAs(UnmanagedType.LPStruct)] DOCINFOA di);

    [DllImport("winspool.Drv", EntryPoint = "EndDocPrinter", SetLastError = true, ExactSpelling = true, CallingConvention = CallingConvention.StdCall)]
    public static extern bool EndDocPrinter(IntPtr hPrinter);

    [DllImport("winspool.Drv", EntryPoint = "StartPagePrinter", SetLastError = true, ExactSpelling = true, CallingConvention = CallingConvention.StdCall)]
    public static extern bool StartPagePrinter(IntPtr hPrinter);

    [DllImport("winspool.Drv", EntryPoint = "EndPagePrinter", SetLastError = true, ExactSpelling = true, CallingConvention = CallingConvention.StdCall)]
    public static extern bool EndPagePrinter(IntPtr hPrinter);

    [DllImport("winspool.Drv", EntryPoint = "WritePrinter", SetLastError = true, ExactSpelling = true, CallingConvention = CallingConvention.StdCall)]
    public static extern bool WritePrinter(IntPtr hPrinter, IntPtr pBytes, Int32 dwCount, out Int32 dwWritten);

    /// 
Method which sends a  array to a printer queue with a specific document name.
    /// Byte array to send to the printer.
    /// Name of the printer to send the  to.
    /// The document Name.
    ///  indicating whether or not the method succeeded at adding something to the print queue.
    public static bool SendBytesToPrinter(byte[] bytes, string printerName, string documentName)
    {
        bool success;

        // Allocate some unmanaged memory for those bytes into an unmanaged pointer.
        IntPtr unmanagedBytes = Marshal.AllocCoTaskMem(bytes.Length);

        // Copy the managed byte array into the unmanaged array.
        Marshal.Copy(bytes, 0, unmanagedBytes, bytes.Length);

        // Send the unmanaged bytes to the printer.
        success = SendUnmanagedBytesToPrinter(unmanagedBytes, printerName, documentName, bytes.Length);

        // Free the unmanaged memory that you allocated earlier.
        Marshal.FreeCoTaskMem(unmanagedBytes);

        return success;
    }

    /// 
Method which sends a string to the printer queue with a specific document name.
    ///  data to send to the printer.
    /// Name of the printer to send the data to.
    /// Name of the document in the printer queue.
    ///  indicating whether or not the method succeeded at adding something to the print queue.
    public static bool SendStringToPrinter(string data, string printerName, string documentName)
    {
        bool success;
        IntPtr unmanagedBytes;

        // How many characters are in the string?
        var characterCount = data.Length;

        // Assume that the printer is expecting ANSI text, and then convert
        // the string to ANSI text.
        unmanagedBytes = Marshal.StringToCoTaskMemAnsi(data);

        // Send the converted ANSI string to the printer.
        success = SendUnmanagedBytesToPrinter(unmanagedBytes, printerName, documentName, characterCount);
        Marshal.FreeCoTaskMem(unmanagedBytes);

        return success;
    }

    private static bool SendUnmanagedBytesToPrinter(IntPtr unmanagedBytes, string printerName, string documentName, int count)
    {
        int error; 
        int written;
        IntPtr printer;
        var di = new DOCINFOA();
        var success = false;

        di.pDocName = documentName;
        di.pDataType = "RAW";

        // Open the printer.
        if (OpenPrinter(printerName.Normalize(), out printer, IntPtr.Zero))
        {
            // Start a document.
            if (StartDocPrinter(printer, 1, di))
            {
                // Start a page.
                if (StartPagePrinter(printer))
                {
                    // Write the bytes.
                    success = WritePrinter(printer, unmanagedBytes, count, out written);
                    EndPagePrinter(printer);
                }

                EndDocPrinter(printer);
            }

            ClosePrinter(printer);
        }

        // If you did not succeed, GetLastError may give more information
        // about why not.
        if (!success)
        {
            error = Marshal.GetLastWin32Error();

            log.ErrorFormat("Sending bytes to printer {0} failed. Last Win32 error = {1}", printerName, error);
        }

        return success;
    }

    // Structure and API declarations:
    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)]
    public class DOCINFOA
    {
        [MarshalAs(UnmanagedType.LPStr)]
        public string pDocName;

        [MarshalAs(UnmanagedType.LPStr)]
        public string pOutputFile;

        [MarshalAs(UnmanagedType.LPStr)]
        public string pDataType;
    }