Reading Data Directly from the Printer

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Introduction

This code will help you to directly fetch information from a network printer using the Printer Job Language. Here, you will have to provide the IP address of your printer and connect to the printer. Once done, you can send commands and retrieve information from the printer directly without using the Windows Spooler. This article will help you in knowing the basics about how to get configuration information, change printer settings, page count, status, toner level etc. from the printer directly.

Background

It started when a need aroused in my organization for some project where we wanted to get the settings and status of a printer directly from the printer, without the use of the Windows Spooler as it has many drawbacks. Also, the accuracy of data is not satisfactory when using the Windows Spooler. So a need aroused to look for different options. At that time, I came to know about this language called PJL (Printer Job Language) which is supported by almost all printer brands in the market. During that time, I wrote this code as an experiment to test its feasibility for implementation. My greatest inspiration behind this code was: Fun With C# and HP Laserjets, which had a funny code written which changes the display message on the printer screen.

Using the code

To understand the code and to execute it, you must have a basic knowledge about IP addresses, socket programming, and PJL (Printer Job Language). You can get the technical reference manuals for PJL from the links given below:

• Printer Job Language - Technical Reference Manual
• HP PJL Reference

Follow these steps in order to execute this code properly:

• Enter the IP address of the printer in the textbox provided.
• Check the printer port number of your network computer and then change it. The default port number of a printer is 9100.
• Press Connect. It will return no error messages if connected successfully, also the Close and Send Command buttons will be enabled.
• Once connected, press on the Send Command button, and it will retrieve the printer configuration data and show it in textbox given below the Send Command button.
• Do not forget to press the Close button once the execution is done, in order to close the connection, else it may happen sometimes that your connection will remain active and other users on the network won't be able to access the printer.

These are few of the PJL commands, and you can execute them one by one. Each command has a specific usage, and throws unique data from the printer. Also, you will have to learn the exact syntax of sending PJL commands to the printer else no data will be received. You can refer the functionality of all the commands from the links provided above.

sendString = String.Format("\x1B%-12345X@PJL INFO PAGECOUNT \r\n\x1B%-12345X\r\n");
sendString = String.Format("\x1B%-12345X@PJL INQUIRE" + 
                           " RESOLUTION \r\n\x1B%-12345X\r\n");
sendString = String.Format("\x1B%-12345X@PJL INQUIRE LPARM :" + 
                           " PCL PITCH \r\n\x1B%-12345X\r\n");
sendString = String.Format("\x1B%-12345X@PJL INFO USTATUS \r\n\x1B%-12345X\r\n");
sendString = String.Format("\x1B%-12345X@PJL INFO STATUS \r\n\x1B%-12345X\r\n");
sendString = String.Format("\x1B%-12345X@PJL INFO MEMORY \r\n\x1B%-12345X\r\n");
sendString = String.Format("\x1B%-12345X@PJL INFO FILESYS \r\n\x1B%-12345X\r\n");
sendString = String.Format("\x1B%-12345X@PJL " + 
                           "DINQUIRE LOWTONER \r\n\x1B%-12345X\r\n");
sendString = String.Format("\x1B%-12345X@PJL INFO CONFIG \r\n\x1B%-12345X\r\n");

Note: PJL can even be destructive; if not properly used, it may change the whole printer setting due to which the printer may give some weird results, and pages may not be printed properly.

Methods

I will give you a basic overview of all the methods in the order they are called.

Connect

The method named cmdConnect_Click is called on pressing the Connect button which tries to connect to the IP address provided, and on failure, it returns an exception message. If successful, then the WaitForData() method is called.

EnableCommands(true);
//Creating instance of Socket
m_socClient = new Socket (AddressFamily.InterNetwork, 
              SocketType.Stream ,ProtocolType.Tcp );

// retrieve the remote machines IP address
IPAddress ip = IPAddress.Parse (txtIPAddr.Text);
//A printer has open port 9100 which 
//can be used to connect to printer
int iPortNo = System.Convert.ToInt16 ( txtPort.Text);
//create the end point 
IPEndPoint ipEnd = new IPEndPoint (ip.Address,iPortNo);
//connect to the remote host
m_socClient.Connect ( ipEnd );
EnableCommands(false);
//wait for data to arrive 
WaitForData();

Wait For Data

The method named WaitForData() keeps on checking for data arrival from the connected port.

if  ( pfnCallBack == null ) 
{
    pfnCallBack = new AsyncCallback (OnDataReceived);
}
CSocketPacket theSocPkt = new CSocketPacket ();
theSocPkt.thisSocket = m_socClient;
// now start to listen for any data which arrives
m_asynResult = m_socClient.BeginReceive (theSocPkt.dataBuffer ,0, 
               theSocPkt.dataBuffer.Length, SocketFlags.None, 
               pfnCallBack,theSocPkt);

Send

The method named cmdSend_Click sends the PJL command to the connected printer after encoding it in the proper format.

string sendString;
sendString = String.Format("\x1B%-12345X@PJL" + 
                           " INFO CONFIG \r\n\x1B%-12345X\r\n");
Object objData = txtDataSend.Text;
byte[] byData = System.Text.Encoding.ASCII.GetBytes(sendString); 
m_socClient.Send (byData);

Receive

The method OnDataReceived is called as soon as the WaitForData method detects any incoming data, and then the received data is decoded and appended byte by byte and displayed in the data-received textbox.

CSocketPacket theSockId = (CSocketPacket)asyn.AsyncState ;
//creating object of the class

//end receive of data
int iReceive  = 0 ;
iReceive = theSockId.thisSocket.EndReceive (asyn);
char[] chars = new char[iReceive +  1];
//creating object for decoding
System.Text.Decoder d = System.Text.Encoding.UTF8.GetDecoder();
int charLen = d.GetChars(theSockId.dataBuffer, 0, iReceive, chars, 0);
System.String szData = new System.String(chars);
txtDataReceive.Text = txtDataReceive.Text + szData;
//as data arrives the bytes are appended to the existing 
//string printer throws data in an ASCII format 1 byte at a time

WaitForData();

Close

The method cmdClose_Click closes the socket connection.

string sendString;
sendString = String.Format("\x1B%-12345X@PJL INFO " + 
                           "CONFIG \r\n\x1B%-12345X\r\n");

Object objData = txtDataSend.Text;
byte[] byData = System.Text.Encoding.ASCII.GetBytes(sendString);
m_socClient.Send (byData);

Points of Interest

It was great fun writing this code and I learnt many unknown characteristics of printers and Windows. I even wrote a small code which made our network printer go crazy: for every page which was being sent for printing, it printed 40 pages. I also learnt many things about the Windows Spooler which also uses a DLL called PJLMON.dll which has an inbuilt PJL command, INFO CONFIG, which gives all the details of a printer which you can see in the Control Panel Printers option.

Currently, I am trying to retrieve data from a printer connected to a local PC via parallel port. Many of my attempts were unsuccessful, but I am still trying. If anyone has any suggestions on it, please mail me at sandeepk31@yahoo.com.

History

This version only works on network printers and also lacks validation, which, if possible, I will implement in the next version.