Printing "raw text" (ZPL) from Web

Question

We have a lot of old ZPL labels.

We would like to be able to print them from a web client. The printer is connected to the client and not the server.

We have had a few ideas:

1. Print from Silverlight. Not feasable. Seems to be no way to print "raw" to Zebra from .NET without calling COM object and that is not posible from plain Silverlight.

2. From Silverlight, treat the ZPL as file and file copy it to printer. Local printer must be setup as shared. Does work from Silverlight Out of Browser with elevated trust. But if posible we would like to avoid Out of browser.

3. If Zebra printer is set to use Generic/Text driver, I can open a ZPL-file in Notepad.exe and send ZPL to printer using File -> Print. In this case the Zebra printer will interpret the text as ZPL instructions and not actual text. Is there any way to "exploit" this from a browser? Have tried a few ways, for example to simply open the ZPL file in the browser and the do File -> Print but that does not seem to work. Have also tried to print from Javascript windows.print();

4. Is there any other plugin (java applet, flash, etc.) capable of sending Raw text (e.g. ZPL) to the Zebra printer?

5. Transform ZPL to images (or pdf:s). Is there any such tool?

Any other ideas?

Answer 1

In Silverlight 5 you can print raw text when you turn on enhanced security. Here is what I did:

private void Button_Click(object sender, RoutedEventArgs e)
{
    StringBuilder label = new StringBuilder();
    label.AppendLine("^XA^MCA^PR8^XZ");
    label.AppendLine("^XA");
    label.AppendLine("^DFCTN^FS");
    label.AppendLine("^LH110,0^FS");
    label.Append("^FO0,60^A0,30,20^FB250,1,0,C,0^FD");
    label.Append(CategoryTextBox.Text.TrimEnd());
    label.AppendLine("^FS");
    label.AppendLine("^FO5,120^A0,40,30^FB250,1,0,C,0^FR^FN1^FS");
    label.AppendLine("^XZ");
    label.AppendLine("^XA");
    label.AppendLine("^XFCTN^FS");
    label.Append("^FO10,100");
    label.Append("^B3N,N,40,Y^FD");
    label.Append(LicensePlateTextBox.Text.TrimEnd());
    label.AppendLine("^FS");
    label.AppendLine("^XZ");

    bool result = RawPrinterHelper.SendStringToPrinter("Zebra Label Printer", label.ToString());
    if (!result)
    {
        MessageBox.Show("Error Returned From Print Spool.  Check Setup.");
    }
}

The RawPrintHelper class:

using System;
using System.IO;
using System.Runtime.InteropServices;
using System.Text;

namespace TestPrinting
{
    public class RawPrinterHelper
    {
        // Structure and API declarions:
        [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;
        }
        [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);

        // SendBytesToPrinter()
        // When the function is given a printer name and an unmanaged array
        // of bytes, the function sends those bytes to the print queue.
        // Returns true on success, false on failure.
        public static bool SendBytesToPrinter(string szPrinterName, IntPtr pBytes, Int32 dwCount)
        {
            Int32 dwError = 0, dwWritten = 0;
            IntPtr hPrinter = new IntPtr(0);
            DOCINFOA di = new DOCINFOA();
            bool bSuccess = false; // Assume failure unless you specifically succeed.

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

            // Open the printer.
            if (OpenPrinter(szPrinterName, out hPrinter, IntPtr.Zero))
            {
                // Start a document.
                if (StartDocPrinter(hPrinter, 1, di))
                {
                    // Start a page.
                    if (StartPagePrinter(hPrinter))
                    {
                        // Write your bytes.
                        bSuccess = WritePrinter(hPrinter, pBytes, dwCount, out dwWritten);
                        EndPagePrinter(hPrinter);
                    }
                    EndDocPrinter(hPrinter);
                }
                ClosePrinter(hPrinter);
            }
            // If you did not succeed, GetLastError may give more information
            // about why not.
            if (bSuccess == false)
            {
                dwError = Marshal.GetLastWin32Error();
            }
            return bSuccess;
        }

        public static bool SendStringToPrinter(string szPrinterName, string pDoc)
        {
            MemoryStream stream = new MemoryStream(Encoding.UTF8.GetBytes(pDoc));
            byte[] rawData = new byte[stream.Length];
            stream.Read(rawData, 0, (int)stream.Length);
            GCHandle rawDataHandle = GCHandle.Alloc(rawData, GCHandleType.Pinned);
            IntPtr pointer = rawDataHandle.AddrOfPinnedObject();
            return SendBytesToPrinter(szPrinterName, pointer, rawData.Length);
        }
    }
}