Sending raw text to printer via usb

Question

I am trying to send ZPL commands to a Zebra ZT230 printer. The printer and drivers are installed and the printer port is "USB003". The PC communicates perfectly with the printer via either Zebra Printer Setup Utilities or ZebraDesign. I tried the following code:

Private Declare Function CreateFile Lib "kernel32.dll" (ByVal lpFileName As String, ByVal dwDesiredAccess As FileAccess, _
ByVal dwShareMode As UInteger, ByVal lpSecurityAttributes As IntPtr, ByVal dwCreationDisposition As FileMode, _
ByVal dwFlagsAndAttributes As UInteger, ByVal hTemplateFile As IntPtr) As System.Runtime.InteropServices.SafeHandle

    ' Command to be sent to the printer
    Dim command As String = "^XA^FO10,10,^AO,30,20^FDFDTesting^FS^FO10,30^BY3^BCN,100,Y,N,N^FDTesting^FS^XZ"
    ' Create a buffer with the command
    Dim buffer() As Byte = New Byte((command.Length) - 1) {}
    buffer = System.Text.Encoding.ASCII.GetBytes(command)
    ' Use the CreateFile external func to connect to the LPT1 port
    Dim printer As System.Runtime.InteropServices.SafeHandle = CreateFile("USB003:", FileAccess.ReadWrite, 0, IntPtr.Zero, FileMode.Open, 0, IntPtr.Zero)
    ' Aqui verifico se a impressora � v�lida
    If (printer.IsInvalid = true) Then
        Return
    End If

    ' Open the filestream to the lpt1 port and send the command
    Dim lpt1 As FileStream = New FileStream(printer, FileAccess.ReadWrite)
    lpt1.Write(buffer, 0, buffer.Length)
    ' Close the FileStream connection
    lpt1.Close 

I get an error on this line: Dim printer As System.Runtime.InteropServices.SafeHandle = CreateFile("USB003:", FileAccess.ReadWrite, 0, IntPtr.Zero, FileMode.Open, 0, IntPtr.Zero)

The error message and stack trace is:

Cannot marshal 'return value': Returned SafeHandles cannot be abstract.

at PerfectPotatoInventory.vb.PotatoGlobals.CreateFile(String& lpFileName, FileAccess dwDesiredAccess, UInt32 dwShareMode, IntPtr lpSecurityAttributes, FileMode dwCreationDisposition, UInt32 dwFlagsAndAttributes, IntPtr hTemplateFile) at PerfectPotatoInventory.vb.PotatoGlobals.PrintLabelsTest() in C:\Potatoes\PerfectPotatoInventory.vb\PerfectPotatoInventory.vb\PotatoGlobals.vb:line 798

I am working in VB.net using VS2008 with target x86 and .Net 3.5.

Please advise what I am doing wrong.

Answer 1

Add this class to your project

Imports System.IO
Imports System.Drawing.Printing
Imports System.Runtime.InteropServices
Public Class RAWPOSPrinter
' Structure and API declarions:
<StructLayout(LayoutKind.Sequential, CharSet:=CharSet.Unicode)> _
Structure DOCINFOW
    <MarshalAs(UnmanagedType.LPWStr)> Public pDocName As String
    <MarshalAs(UnmanagedType.LPWStr)> Public pOutputFile As String
    <MarshalAs(UnmanagedType.LPWStr)> Public pDataType As String
End Structure

<DllImport("winspool.Drv", EntryPoint:="OpenPrinterW", _
   SetLastError:=True, CharSet:=CharSet.Unicode, _
   ExactSpelling:=True, CallingConvention:=CallingConvention.StdCall)> _
Public Shared Function OpenPrinter(ByVal src As String, ByRef hPrinter As IntPtr, ByVal pd As Long) As Boolean
End Function
<DllImport("winspool.Drv", EntryPoint:="ClosePrinter", _
   SetLastError:=True, CharSet:=CharSet.Unicode, _
   ExactSpelling:=True, CallingConvention:=CallingConvention.StdCall)> _
Public Shared Function ClosePrinter(ByVal hPrinter As IntPtr) As Boolean
End Function
<DllImport("winspool.Drv", EntryPoint:="StartDocPrinterW", _
   SetLastError:=True, CharSet:=CharSet.Unicode, _
   ExactSpelling:=True, CallingConvention:=CallingConvention.StdCall)> _
Public Shared Function StartDocPrinter(ByVal hPrinter As IntPtr, ByVal level As Int32, ByRef pDI As DOCINFOW) As Boolean
End Function
<DllImport("winspool.Drv", EntryPoint:="EndDocPrinter", _
   SetLastError:=True, CharSet:=CharSet.Unicode, _
   ExactSpelling:=True, CallingConvention:=CallingConvention.StdCall)> _
Public Shared Function EndDocPrinter(ByVal hPrinter As IntPtr) As Boolean
End Function
<DllImport("winspool.Drv", EntryPoint:="StartPagePrinter", _
   SetLastError:=True, CharSet:=CharSet.Unicode, _
   ExactSpelling:=True, CallingConvention:=CallingConvention.StdCall)> _
Public Shared Function StartPagePrinter(ByVal hPrinter As IntPtr) As Boolean
End Function
<DllImport("winspool.Drv", EntryPoint:="EndPagePrinter", _
   SetLastError:=True, CharSet:=CharSet.Unicode, _
   ExactSpelling:=True, CallingConvention:=CallingConvention.StdCall)> _
Public Shared Function EndPagePrinter(ByVal hPrinter As IntPtr) As Boolean
End Function
<DllImport("winspool.Drv", EntryPoint:="WritePrinter", _
   SetLastError:=True, CharSet:=CharSet.Unicode, _
   ExactSpelling:=True, CallingConvention:=CallingConvention.StdCall)> _
Public Shared Function WritePrinter(ByVal hPrinter As IntPtr, ByVal pBytes As IntPtr, ByVal dwCount As Int32, ByRef dwWritten As Int32) As Boolean
End Function

' 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 or False on failure.
Public Shared Function SendBytesToPrinter(ByVal szPrinterName As String, ByVal pBytes As IntPtr, ByVal dwCount As Int32) As Boolean
    Dim hPrinter As IntPtr      ' The printer handle.
    Dim dwError As Int32        ' Last error - in case there was trouble.
    Dim di As DOCINFOW          ' Describes your document (name, port, data type).
    Dim dwWritten As Int32      ' The number of bytes written by WritePrinter().
    Dim bSuccess As Boolean     ' Your success code.

    ' Set up the DOCINFO structure.
    di = New DOCINFOW
    With di
        .pDocName = "RAW DOC"
        .pDataType = "RAW"
    End With
    ' Assume failure unless you specifically succeed.
    bSuccess = False
    If OpenPrinter(szPrinterName, hPrinter, 0) Then
        If StartDocPrinter(hPrinter, 1, di) Then
            If StartPagePrinter(hPrinter) Then
                ' Write your printer-specific bytes to the printer.
                bSuccess = WritePrinter(hPrinter, pBytes, dwCount, dwWritten)
                EndPagePrinter(hPrinter)
            End If
            EndDocPrinter(hPrinter)
        End If
        ClosePrinter(hPrinter)
    End If
    ' If you did not succeed, GetLastError may give more information
    ' about why not.
    If bSuccess = False Then
        dwError = Marshal.GetLastWin32Error()
    End If
    Return bSuccess
End Function ' SendBytesToPrinter()

' SendFileToPrinter()
' When the function is given a file name and a printer name, 
' the function reads the contents of the file and sends the
' contents to the printer.
' Presumes that the file contains printer-ready data.
' Shows how to use the SendBytesToPrinter function.
' Returns True on success or False on failure.
Public Shared Function SendFileToPrinter(ByVal szPrinterName As String, ByVal szFileName As String) As Boolean
    ' Open the file.
    Dim fs As New FileStream(szFileName, FileMode.Open)
    ' Create a BinaryReader on the file.
    Dim br As New BinaryReader(fs)
    ' Dim an array of bytes large enough to hold the file's contents.
    Dim bytes(fs.Length) As Byte
    Dim bSuccess As Boolean
    ' Your unmanaged pointer.
    Dim pUnmanagedBytes As IntPtr

    ' Read the contents of the file into the array.
    bytes = br.ReadBytes(fs.Length)
    ' Allocate some unmanaged memory for those bytes.
    pUnmanagedBytes = Marshal.AllocCoTaskMem(fs.Length)
    ' Copy the managed byte array into the unmanaged array.
    Marshal.Copy(bytes, 0, pUnmanagedBytes, fs.Length)
    ' Send the unmanaged bytes to the printer.
    bSuccess = SendBytesToPrinter(szPrinterName, pUnmanagedBytes, fs.Length)
    ' Free the unmanaged memory that you allocated earlier.
    Marshal.FreeCoTaskMem(pUnmanagedBytes)
    Return bSuccess
End Function ' SendFileToPrinter()

' When the function is given a string and a printer name,
' the function sends the string to the printer as raw bytes.
Public Shared Sub SendStringToPrinter(ByVal szPrinterName As String, ByVal szString As String)
    Dim pBytes As IntPtr
    Dim dwCount As Int32
    ' How many characters are in the string?
    dwCount = szString.Length()
    ' Assume that the printer is expecting ANSI text, and then convert
    ' the string to ANSI text.
    pBytes = Marshal.StringToCoTaskMemAnsi(szString)
    ' Send the converted ANSI string to the printer.
    SendBytesToPrinter(szPrinterName, pBytes, dwCount)
    Marshal.FreeCoTaskMem(pBytes)
End Sub
End Class

Then in your code, call the following:

RAWPOSPrinter.SendStringToPrinter("<NAME OF PRINTER AS IT APPEARS IN DEVICES AND PRINTERS>", "<YOUR ZEBRA COMMAND STRING>")

Answer 2

Using the Zebra .Net SDK you can call the following function: PrinterUtil.SendContents Method (String, String)

Where the first string is the ZPL to send and the second string is the printer connection string. More detail can be found here: http://techdocs.zebra.com/link-os/2-14/pc_net/