How to read back status from Zebra receipt printer?

Question

I'm using a Zebra KR403 receipt printer for a project and I need to programatically read the status from the printer (out of paper, paper near-end, printhead open, paper jam, etc). In the ZPL documentation I found that I need to send a ~HQES command and the printer responds with its status information.

In the project the printer is connected via USB, but I figured it may be easier to get it to work connecting it via COM port and work from there to get it to work over USB. I am able to open communication with the printer and send commands to it (I can print test receipts), but whenever I try to read anything back it simply hangs forever and never gets to read anything.

Here's the code I'm using:

public Form1()
{
    InitializeComponent();
    SendToPrinter("COM1:", "^XA^FO50,10^A0N50,50^FDKR403 PRINT TEST^FS^XZ", false); // this prints OK
    SendToPrinter("COM1:", "~HQES", true); // read is never completed
}

[DllImport("kernel32.dll", SetLastError = true)]
static extern SafeFileHandle CreateFile(
    string lpFileName, 
    FileAccess dwDesiredAccess,
    uint dwShareMode, 
    IntPtr lpSecurityAttributes, 
    FileMode dwCreationDisposition,
    uint dwFlagsAndAttributes, 
    IntPtr hTemplateFile);

private int SendToPrinter(string port, string command, bool readFromPrinter)
{
    int read = -2;

    // Create a buffer with the command
    Byte[] buffer = new byte[command.Length];
    buffer = System.Text.Encoding.ASCII.GetBytes(command);

    // Use the CreateFile external func to connect to the printer port
    using (SafeFileHandle printer = CreateFile(port, FileAccess.ReadWrite, 0, IntPtr.Zero, FileMode.Open, 0, IntPtr.Zero))
    {
        if (!printer.IsInvalid)
        {
            using (FileStream stream = new FileStream(printer, FileAccess.ReadWrite))
            {
                stream.Write(buffer, 0, buffer.Length);

                // tries to read only one byte (for testing purposes; in reality many bytes will be read with the complete message)
                if (readFromPrinter)
                {
                    read = stream.ReadByte(); // THE PROGRAM ALWAYS HANGS HERE!!!!!!
                }

                stream.Close();
            }
        }
    }

    return read;
}

I've found out that when I print the test receipt (first call to SendToPrinter()) nothing gets printed until I close the handle with stream.Close(). I've made these tests but to no avail:

calling stream.Flush() after calling stream.Write(), but still nothing gets read (and nothing gets printed either until I call stream.Close())
only send command and then close the stream, immediately reopen and try to read
open two handles, write on handle 1, close handle 1, read handle 2. nothing

Has anyone has had any luck reading back status from a Zebra printer? Or anyone has any idea of what I may be doing wrong?

I think you'll get more traction (better control) using the [SerialPort](http://msdn.microsoft.com/en-us/library/system.io.ports.serialport.aspx) class than a generic FileStream for this. — 500 - Internal Server Error, Mar 07 '13 at 18:46
@500-InternalServerError right now I'm connecting it via COM port because I figured that would be easier than USB to start with, but in the actual project the printer is connected via USB so SerialPort class is not an option here. — MarioVW, Mar 07 '13 at 19:22
Why not? As the name implies, USB ports are serial ports too. — 500 - Internal Server Error, Mar 07 '13 at 19:25
@500-InternalServerError the SerialPort class is for handling RS232/COM ports, USB is a bus (not a port) and its internal workings are completely different from RS232 (and cannot be accessed through SerialPort class, unless you have a Virtual COM port but that's a different story) — MarioVW, Mar 07 '13 at 19:39
Good point - I was thinking of the virtual COM port scenario, which the USB printers I've encountered have in fact provided, but I guess they don't have to. — 500 - Internal Server Error, Mar 07 '13 at 19:43
This looks to have already been answered by someone trying to do exactly the same as you [over here](http://stackoverflow.com/questions/15363941/which-sdk-should-i-use-for-kr403-zebra-printer). — l33tmike, May 29 '13 at 15:44
@l33tmike please add an answer with the link so I can mark it as accepted for further reference. I had already looked at that question but before the update with the link was posted. — MarioVW, May 30 '13 at 15:50
As a general rule for RS232 communications, double check your Baud Rate, Stop Bits & Parity settings and make sure they match those of the device. Plus, not all RS232 cables are created equally. — Phill, Jul 31 '13 at 15:42

score 0 · Accepted Answer · edited May 23 '17 at 12:06

0

As pointed out by @l33tmike in the comments, the answer to this question has already been posted on another question: Which SDK should I use for KR403 Zebra Printer

edited May 23 '17 at 12:06

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answered Aug 01 '13 at 19:59

MarioVW

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How to read back status from Zebra receipt printer?

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