Hi all,
I am currently developing a java application that will allow the user
to perform wake on lan. The program gets the host name and mac address
from a CSV file. When the user presses the button the application will
read the file in and then perform the wake on lan on the computer.
However I keep on getting an error and the application is not working.
This is the error that i am getting.
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at remoteshutdown.WakeOnLan.WOL(WakeOnLan.java:74)
at remoteshutdown.WakeOnLan.readFile(WakeOnLan.java:60)
at
remoteshutdown.mainScreen.btnAddDetails_actionPerformed(mainScreen.java:
563)
at remoteshutdown.mainScreen
$mainScreen_btnAddDetails_actionAdapter.actionPerformed(mainScreen.java:
980)
at javax.swing.AbstractButton.fireActionPerformed(Unknown Source)
at javax.swing.AbstractButton$Handler.actionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.fireActionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.setPressed(Unknown Source)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(Unknown
Source)
at java.awt.Component.processMouseEvent(Unknown Source)
at javax.swing.JComponent.processMouseEvent(Unknown Source)
at java.awt.Component.processEvent(Unknown Source)
at java.awt.Container.processEvent(Unknown Source)
at java.awt.Component.dispatchEventImpl(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Window.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown
Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown
Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)
This is the code that I am using:
package remoteshutdown;
im****t java.awt.Dimension;
im****t java.awt.Point;
im****t java.io.*;
im****t java.net.*;
im****t java.util.*;
public class WakeOnLan {
String macStr;
// String mac;
// String Computer;
Hashtable<String, String> macTable = new Hashtable<String,
String>();
public static final int ****T = 9;
public void readFile() {
try {
// Open the file that is the first
// command line parameter
FileInputStream fstream = new FileInputStream("C:\
\Do***ents and Settings\\All Users\\Application Data\\Remote Shutdown\
\DHCP Ex****t.csv");
// Get the object of DataInputStream
DataInputStream in = new DataInputStream(fstream);
BufferedReader br = new BufferedReader(new
InputStreamReader(fstream));
String strLine;
//Read File Line By Line
while ((strLine = br.readLine()) != null) {
System.out.println("strLine is: " + strLine );
StringTokenizer st = new StringTokenizer(strLine, ",.");
String Computer = st.nextToken();
if(strLine.contains("."))
{
int firstIndex = strLine.indexOf(".");
int lastIndex = strLine.lastIndexOf(".");
if (firstIndex == lastIndex) {
st.nextToken();
}
else {
st.nextToken();
st.nextToken();
}
}
String mac = st.nextToken();
System.out.println("\t\tComputer : " + Computer+" for
"+mac);
macTable.put((String)Computer, (String)mac);
// Print the content on the console
//Close the input stream
}
System.out.println("CLOSING IN");
in.close();
} catch (Exception e) { //Catch exception if any
System.err.println("Error: " + e.toString());
}
WOL();
}
public void WOL() {
Object[] choices =
mainScreen.lstComputerNames.getSelectedValues();
for (Object aChoice : choices) {
String wakeComputer = (String)macTable.get(aChoice);
System.out.println("wakeComputer is:" + wakeComputer);
String ipStr = "255.255.255.255"; //broadcast address
String originalMac = wakeComputer.substring(0,2) + ":" +
wakeComputer.substring(2,4) + ":" + wakeComputer.substring(4,6) + ":"
+ wakeComputer.substring(6,8) + ":" + wakeComputer.substring(8, 10) +
":" + wakeComputer.substring(10,12);
System.out.println("original mac: " + originalMac);
String macStr = originalMac; //"00:30:4F:1C:95:dF";
try {
// wait(5000);
byte[] macBytes = getMacBytes(macStr);
byte[] bytes = new byte[6 + 16 * macBytes.length];
for (int i = 0; i < 6; i++) {
bytes[i] = (byte) 0xff;
}
for (int i = 6; i < bytes.length; i += macBytes.length) {
System.arraycopy(macBytes, 0, bytes, i,
macBytes.length);
}
InetAddress address = InetAddress.getByName(ipStr);
DatagramPacket packet = new DatagramPacket(bytes,
bytes.length, address, ****T);
DatagramSocket socket = new DatagramSocket();
socket.send(packet);
socket.close();
System.out.println("Wake-on-LAN packet sent.");
}
catch (Exception e) {
System.out.println("Failed to send Wake-on-LAN packet: +
e");
System.exit(1);
}
}
}
private static byte[] getMacBytes(String macStr) throws
IllegalArgumentException {
byte[] bytes = new byte[6];
String[] hex = macStr.split("(\\:|\\-)");
if (hex.length != 6) {
throw new IllegalArgumentException("Invalid MAC
address.");
}
try {
for (int i = 0; i < 6; i++) {
bytes[i] = (byte) Integer.parseInt(hex[i], 16);
}
}
catch (NumberFormatException e) {
throw new IllegalArgumentException("Invalid hex digit in
MAC address.");
}
return bytes;
}
}
Any help in this matter would be highly appreciated. Thank you
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