POS Terminal interface via COM

Question

I am developing and interface between a java application and a POS terminal for credit card payment.
I have implemented a very simple class to Read data on COM port to which the POS is linked.
This is the code
package com.bnt.iso.util.serial;
import java.io.IOException;
import java.io.InputStream;
import java.util.TooManyListenersException;
import gnu.io.CommPort;
import gnu.io.CommPortIdentifier;
import gnu.io.NoSuchPortException;
import gnu.io.PortInUseException;
import gnu.io.SerialPort;
import gnu.io.SerialPortEvent;
import gnu.io.SerialPortEventListener;
import gnu.io.UnsupportedCommOperationException;
import com.bnt.iso.util.serial.*;
public class ReadSerialPort implements SerialPortEventListener,Runnable {
     InputStream input;
     Thread readThread;
     SerialPort porta_seriale;
     static CommPortIdentifier id_porta;
     int k=0;
      String result;
      byte[] readBuffer = new byte[128];
      int numBytes;
     public ReadSerialPort(String port)  {
          try{
               id_porta= CommPortIdentifier.getPortIdentifier("COM1");
               CommPort porta=(SerialPort)id_porta.open("ReadSerialPort",200);
                porta_seriale=(SerialPort)porta;
               input=porta.getInputStream();
               porta_seriale.addEventListener(this);
               porta_seriale.notifyOnDataAvailable(true);
               porta_seriale.notifyOnOutputEmpty(true);
               porta_seriale.notifyOnDSR(true);
               porta_seriale.notifyOnBreakInterrupt(true);
               porta_seriale.notifyOnCarrierDetect(true);
               porta_seriale.notifyOnCTS(true);
               porta_seriale.notifyOnFramingError(true);
               porta_seriale.notifyOnOverrunError(true);
               porta_seriale.notifyOnParityError(true);
               porta_seriale.notifyOnRingIndicator(true);
               porta_seriale.setSerialPortParams(9600,
                            SerialPort.DATABITS_8,
                            SerialPort.STOPBITS_1,
                            SerialPort.PARITY_NONE);
                readThread = new Thread(this);
               readThread.start();
               catch(NoSuchPortException ne){
                 System.out.println("Serial Port COM2 NOT Present");
               }catch(PortInUseException pe){
                 System.out.println("Serial Port COM2 owned by "+pe.currentOwner);
               }catch(UnsupportedCommOperationException ue){
                 System.out.println("Serial Port mismatch with params used");
               }catch(IOException ioe){
                 System.out.println("IO Error");
               catch (TooManyListenersException tme){
                    System.out.println("Only one listener");
               catch(Exception e){
                    System.out.println("Only one listener");
     //25757575750575449115495050505649575255310
     //25757575750575449115495050505649575255310
     //257575757505754491154950505056495752550310
     public  void run()
          try{
               Thread.sleep(60000);
               porta_seriale.close();
          catch(InterruptedException e){}
     public  void serialEvent(SerialPortEvent event) {
          System.out.println(" \n Start Event");
          switch (event.getEventType())
               case SerialPortEvent.BI:
                    System.out.print("Case BI");
               case SerialPortEvent.OE:
                    System.out.print("Case OE");
               case SerialPortEvent.FE:     
                    System.out.print("Case FE");
               case SerialPortEvent.PE:
                    System.out.print("Case PE");
               case SerialPortEvent.CD:
                    System.out.print("Case CD");
               case SerialPortEvent.CTS:
                    System.out.print("Case CTS");
               case SerialPortEvent.DSR:
                    System.out.print("Case DSR");
               case SerialPortEvent.RI:
                    System.out.print("Case RI");
               case SerialPortEvent.OUTPUT_BUFFER_EMPTY:
                     System.out.print("dati non disponibili");
                    break;
               case SerialPortEvent.DATA_AVAILABLE:
                    System.out.print("Dati disponibili \n");
                    byte[] readBuffer = new byte[16];
                    try {
                         while (input. available()>0) {                              
                               numBytes = input.read(readBuffer);                              
                          System.out.print(new String (readBuffer));
                          System.out.print("\n");
                          System.out.print(CCard_Int_Util.stringToHex(new String (readBuffer)));
                     catch (IOException e) {
                          System.out.print("IO exception " +e.getStackTrace());
                          break;
     public  static void main (String[] args){
          char STX = (char)0x02;
           char ETX = (char)0x03;
           char ACK = (char)06;
           char LRC_7A = (char)0x7A;
           char LRC_3D = (char)0x3D;
           char NP_13 =  (char)13;
           char NP_12 =  (char)12;
           char NP_46 =  (char)46;
           char NP_26 =  (char)26; //1A
           char NP_61  = (char)61;
           String codComm = "000000";
           String idTerminal = "00";
           String filler = "000";
           String ackPos = "0"; //2
           String CardType = "0";
           String infoCard = "0";
           String closePOS = STX+"000000000C"+ETX+NP_13;
           String openPOS = STX+"000000000B"+ETX+NP_12;
//           String payPOS = STX + codComm + idTerminal + "P" + "000000000"+ETX+NP_46;
           String tot =       STX + "000000000" + "I" + "00000,100000000000"+ETX+""+NP_26;
           String payPOS =STX + "000000000I00000,10"+"0" + ETX + "" + NP_46;
           String Import_payPOS =STX + "000000000P000000000" + ETX + "" + NP_46;
           String ACK_Mex = ACK + "" + ETX + "" +LRC_7A;
           String Status = STX+"000000000s"+ETX+""+NP_61;
           //ControlSerialPortNT.WriteSerialPortNT(openPOS);
           ControlSerialPortNT.WriteSerialPortNT(payPOS);
          ReadSerialPort read= new ReadSerialPort("COM1");
               try {
                    read.finalize();
               } catch (Throwable e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
}The problem is that
Performing EXACTLY the same actions sometimes the response of the POS is the following
FIRST CASE :
Read Event 1
2393939393239363031493b000
SECOND CASE :
Read Event 1
23939393932393600000000
Read Evcet 2
3031493b00000000000
Do you think that this could be a problem of synchronyzation or something like that or it is possibly a problem of the hardware ?
Thanks a lot.

Answer 1

The program is intended for personal use, so yes, practice. In total, I want my program to provide a new interface for command.com. I want to learn how to use the in/out streams of command.com to achieve this. Currently I am substituting cmd.exe for command.com because java won't display the input stream properly (alternate encoding perhaps? I don't know enough about encodings or command.com though). But I'm not worrying about that so much as how to pass a command to the process. I've tried writing the string of a command with and without the \n character to the output stream, but it doesn't cause the input stream to change at all. The only way I have successfully executed a command is by using batch mode, so that is the big problem with this right now.
Edit: I am aware that you can execute commands one-at-a-time by using parameters, it just seems silly to have to re-run the process every time i need something.
Edited by: R_Neufeld on Aug 4, 2008 9:36 PM