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PONull Pointer Exception when accessing the serial port
 

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  1. PONull Pointer Exception when accessing the serial port
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    <p>I have a Java project (in NetBeans 7.1) and I am receiving the following <code>NullPointerException</code>:</p> <pre><code>run: Port COM10 not found. The serial port you are trying to use is currently in usejava.lang.NullPointerException Exception in thread "main" java.lang.NullPointerException at mateorssms.Communicator.ListenOnPort(Communicator.java:68) at mateorssms.Communicator.&lt;init&gt;(Communicator.java:35) at mateorssms.MateorsSMS.main(MateorsSMS.java:14) Java Result: 1 BUILD SUCCESSFUL (total time: 1 second). </code></pre> <p>So my MateorsSMS class is:</p> <pre><code>package mateorssms; import java.awt.Frame; public class MateorsSMS{ public static void main(String[] args) { //UserInterface UI = new UserInterface(); //UI.setVisible(true); new Communicator(); // TODO code application logic here } } </code></pre> <p>and Communicator class (different class in a different file) is</p> <pre><code>package mateorssms; import java.io.IOException; import java.io.InputStream; import javax.comm.*; import java.util.Enumeration; import java.util.TooManyListenersException; public class Communicator implements Runnable, SerialPortEventListener{ static Enumeration portList; static CommPortIdentifier portId; boolean portFound = false; SerialPort serialPort; String defaultPort = "COM10"; Thread readThread; InputStream inputStream; public Communicator(){ getPort(); ListenOnPort(); } private void getPort(){ ////////////////////////////////////////////////////////////////////////////// portFound = false; portList = CommPortIdentifier.getPortIdentifiers(); while(portList.hasMoreElements() &amp;&amp; !(portFound)){ portId = (CommPortIdentifier) portList.nextElement(); if(portId.getPortType() == CommPortIdentifier.PORT_SERIAL){ if(portId.getName().equals(defaultPort)){ System.out.println("Found port: " + defaultPort); portFound = true; } } } if(!portFound){ System.err.println("Port " + defaultPort + " not found."); //user feedback //System.exit(1); } } private void ListenOnPort(){ try { serialPort = (SerialPort) portId.open("MateorsSMSApp", 300); System.out.println("yes"); } catch (Exception e) { System.out.println("The serial port you are trying to use is currently in use"+e.toString()); } try { inputStream = serialPort.getInputStream(); System.out.println(inputStream.toString()); } catch (IOException e) { System.err.println("Ex"); } try { serialPort.addEventListener(this); } catch (TooManyListenersException e) { System.err.println("Ex"); } // activate the DATA_AVAILABLE notifier serialPort.notifyOnDataAvailable(true); try { serialPort.setSerialPortParams(460800, SerialPort.DATABITS_8, SerialPort.STOPBITS_1, SerialPort.PARITY_NONE); serialPort.setDTR(true); serialPort.setRTS(true); } catch (UnsupportedCommOperationException e) { System.err.println("Ex"); } readThread = new Thread(this); readThread.start(); } @Override public void serialEvent(SerialPortEvent event) { switch (event.getEventType()) { case SerialPortEvent.BI: System.out.println("BI"); // Break interruptbreak; case SerialPortEvent.OE: System.out.println("OE");// Overrun error break; case SerialPortEvent.FE: System.out.println("FE");// Framing error break; case SerialPortEvent.PE: System.out.println("PE");// Parity error break; case SerialPortEvent.CD: System.out.println("CD");//Carrier detected break; case SerialPortEvent.CTS: System.out.println("CTS");//Clear to send break; case SerialPortEvent.DSR: System.out.println("DSR");// Data set ready break; case SerialPortEvent.RI: System.out.println("RI");// Ring indicator break; case SerialPortEvent.OUTPUT_BUFFER_EMPTY: System.out.println("OUTPUT_BUFFER_EMPTY"); //break; //break; //Buffer empty case SerialPortEvent.DATA_AVAILABLE: //Data Available to be read System.out.println("DATA_AVAILABLE"); byte[] readBuffer = new byte[20]; try { while (inputStream.available() &gt; 0) { int numBytes = inputStream.read(readBuffer); } String result = new String(readBuffer); System.out.println(result); } catch (IOException e) { System.err.println("Ex"); } break; } //SerialPort port; // TODO do something with ev } @Override public void run(){ try { Thread.sleep(3000); } catch (InterruptedException ex){ System.err.println("Ex"); } } } </code></pre>
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    1. USA. K. M. Tariqul Islam
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    1. COLooks like the COM port you're trying to use is busy. Try different serial ports until you come to know it's not in use.
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