Zebra EPL printer status commands
Wali Akthar
Our clients use quite a few mixed zebra label printers to print out address labels and we have a problem whereby the volume of labels that need to be printed causes some problems. When a lot of print jobs are sent to a label printer, it seems to print some, miss a few out then print another batch.
Problem:
How to obtain label printer status codes.
Printer details: Zebra GK420d and LP 2844, it has to work for both types so can only use EPL commands.
I am trying to obtain whether a job sent to a label printer has successfully completed or not so I can send the next print job.
I have tried various commands such as ^ee, eR, US and finally ~HS commands.
The only command that responds is the ~HS command, so I’m checking the buffer full flag to see if it is ok to send the next print job.
This works well until I get a buffer full response, so my test application will continually send the ~HS command until the buffer full flag is set back to 0, then I continue to send print jobs.
Then suddenly the printer stops responding, the red led appears and the printer fails to print any further jobs!
I have a simple test application (C#) as follows:
private void StartReceive(object state)
{
var labelPrinter = "xx.xx.xx.xx";
var client = new TcpClient();
try
{
client.SendTimeout = 30000;
client.ReceiveTimeout = 30000;
client.Connect(labelPrinter, _portNumber);
var nStream = client.GetStream();
while (true)
{
var sReader = new StreamReader(nStream);
var readBuffer = new char[1000];
sReader.Read(readBuffer, 0, readBuffer.Length);
PrinterStatusResponse(new string(readBuffer));
}
}
catch (Exception ex)
{
Console.WriteLine("{0} {1} - EXCEPTION ( {2} )", DateTime.Now.ToShortDateString(),
DateTime.Now.ToLongTimeString(), ex.Message);
}
}
private void PrinterStatusResponse(string data)
{
_okToSend = true;
if (string.IsNullOrEmpty(data)) return;
if (_STATUS_REPORTING_COMMAND == "~HS")
{
var args = data.Split(',');
Console.WriteLine("{0} {1} - RECEIVED DATA {2}", DateTime.Now.ToShortDateString(), DateTime.Now.ToLongTimeString(), data.Substring(0, 34));
// Check buffer full flag (1 = receive buffer full)
if (args.Length > 6 && args[5] != null)
{
_okToSend = (args[5] == "0");
Console.WriteLine("{0} {1} - PrinterStatusResponse okToSend = {2} after checking buffer full flag", DateTime.Now.ToShortDateString(),
DateTime.Now.ToLongTimeString(), _okToSend);
Console.WriteLine("NUMBER OF FORMATS IN BUFFER = {0}", args[4]);
}
}
}
private void SendCommand(object state)
{
Console.WriteLine("{0} {1} - SendCommand called", DateTime.Now.ToShortDateString(), DateTime.Now.ToLongTimeString());
while (true)
{
if (_client != null && _client.Connected && _queue.Count > 0)
{
try
{
Console.WriteLine("{0} {1} - Messages in queue {2}", DateTime.Now.ToShortDateString(), DateTime.Now.ToLongTimeString(), _queue.Count);
// Wait to see if we can send
while (!_okToSend)
{
Thread.Sleep(50);
Console.WriteLine("{0} {1} - SendCommand WAITING for okToSend", DateTime.Now.ToShortDateString(), DateTime.Now.ToLongTimeString());
}
LabelMessage message;
Monitor.Enter(_queue);
try
{
message = _queue.Dequeue();
}
finally
{
Monitor.Exit(_queue);
}
if (message != null)
{
var sWriter = new StreamWriter(_nStream);
sWriter.WriteLine(message.LabelContent.ToString());
sWriter.Flush();
Console.WriteLine("{0} {1} - SendCommand sent for printing", DateTime.Now.ToShortDateString(), DateTime.Now.ToLongTimeString());
}
else Console.WriteLine("{0} {1} - No messages to send", DateTime.Now.ToShortDateString(), DateTime.Now.ToLongTimeString());
_counter++;
_messageCount++;
if (_counter > (_labelsToPrint.Length - 1)) _counter = 0;
Console.WriteLine("{0} {1} - SendCommand sent for printing MESSAGECOUNT={2}", DateTime.Now.ToShortDateString(), DateTime.Now.ToLongTimeString(), _messageCount);
}
catch (Exception ex)
{
Console.WriteLine("{0} {1} - EXCEPTION ( {2} )", DateTime.Now.ToShortDateString(), DateTime.Now.ToLongTimeString(), ex.Message);
}
}
}
}
private void SendStatusCheck(object state)
{
if (_client.Connected)
{
try
{
Console.WriteLine("{0} {1} - Sending status check", DateTime.Now.ToShortDateString(), DateTime.Now.ToLongTimeString());
var sWriter = new StreamWriter(_nStream);
sWriter.WriteLine("~HS");
sWriter.Flush();
Console.WriteLine("Sent {0} Command .. Waiting for Printer Reply...", _STATUS_REPORTING_COMMAND);
}
catch (Exception ex)
{
Console.WriteLine("{0} {1} - EXCEPTION ( {2} )", DateTime.Now.ToShortDateString(), DateTime.Now.ToLongTimeString(), ex.Message);
}
}
}
private void ConnectClient()
{
var labelPrinter = "xx.xx.xx.xx";
_client = new TcpClient();
try
{
_client.SendTimeout = 30000;
_client.ReceiveTimeout = 30000;
_client.Connect(labelPrinter, _portNumber);
_nStream = _client.GetStream();
var sWriter = new StreamWriter(_nStream);
sWriter.WriteLine("~JA");
sWriter.Flush();
Console.WriteLine("{0} {1} - Connected to Printer {2} ", DateTime.Now.ToShortDateString(), DateTime.Now.ToLongTimeString(), labelPrinter);
btnSend.Enabled = true;
ThreadPool.QueueUserWorkItem(StartReceive);
timer1.Start(); // this continually calls SendStatusCheck
timer2.Start(); // this continually calls SendCommand
}
catch(Exception ex)
{
Console.WriteLine("{0} {1} - EXCEPTION ( {2} )", DateTime.Now.ToShortDateString(), DateTime.Now.ToLongTimeString(), ex.Message);
}
}
Why does the printer show a red led after a certain number of prints and stops responding? Am I using the correct code (~HS) to check whether I can send another print job?
Please can you provide details on how I could solve these issues or provide contacts which may be able to help.
Tres Finocchiaro
we have a problem whereby the volume of labels that need to be printed causes some problems
I am trying to obtain whether a job sent to a label printer has successfully completed or not so I can send the next print job.
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