Help in stopping thread (Packet sniffer)

[adilet23]

Hi! I'm confused with this code. I have a problem with stopping the thread. Can anybody help me?

Thank you! Hope for your help guys.

Code:

import java.util.logging.Level;
import java.util.logging.Logger;
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import jpcap.JpcapCaptor;
import jpcap.NetworkInterface;
import jpcap.PacketReceiver;
import jpcap.packet.*;
 
public class MainGUI extends JFrame{
 
	private JLabel lblintro;
	public JTextArea txtPackets;
	public JTextArea txtWarnings;
	private JPanel panel1;
        private JPanel panel2;
        private JPanel panel3;
        private JPanel panel4;
        private JPanel panel5;
	private JButton btnStart;
	private JButton btnStop;
	private JButton btnExit;
	private JScrollPane sbrText;
	public  JpcapCaptor jpcap;
	public TestPacketReceiver TPR;
        protected JTabbedPane tabPane;
 
	public MainGUI(){
 
		super("Packet Sniffer");
 
                tabPane = new JTabbedPane();
                panel1 = new JPanel();
                panel3 = new JPanel();
                tabPane.addTab("Main menu", null,panel1,"First panel");
 
                lblintro = new JLabel ("Packet Sniffer");
                panel1.setLayout(new BorderLayout());
                panel1.add(panel3,BorderLayout.NORTH);
 
                panel3.setLayout(new FlowLayout());
                panel3.add(lblintro);
 
                btnStart = new JButton ("Start");
                btnStart.addActionListener(new ButtonListener());
                btnStop = new JButton ("Stop");
		btnStop.addActionListener(new ButtonListener());
                btnExit = new JButton ("Exit");
		btnExit.addActionListener(new ButtonListener());
 
                panel3.add(btnStart);
                panel3.add(btnStop);
                panel3.add(btnExit);
 
                txtPackets = new JTextArea ();
                txtPackets.setLineWrap(true);
		txtPackets.setBorder(BorderFactory.createTitledBorder("Packets"));
                panel1.add(txtPackets,BorderLayout.CENTER);
 
                panel5 = new JPanel();
                panel1.add(panel5,BorderLayout.SOUTH);
 
                txtWarnings = new JTextArea ();
		txtWarnings.setLineWrap(true);
                txtWarnings.setBorder(BorderFactory.createTitledBorder("Warnings"));
                panel1.add(txtWarnings,BorderLayout.SOUTH);
 
                panel2 = new JPanel();
                tabPane.addTab("Logs", null, panel2, "Second panel");
                panel4 = new JPanel();
                tabPane.addTab("Send alerts",null,panel4);
                add(tabPane);                
	}
 
 
	 java.lang.Runnable rnner=new Runnable(){
            public void run(){
                jpcap.loopPacket(-1, new TestPacketReceiver());
            }
         };
         Thread t;
 
	 public void startCapThread(final JpcapCaptor jpcap){	  
            t =  new Thread(rnner);
            t.start();
         }    
 
//////////////////// This part below is not working ////////////////////////
 
	public void stopthread (final JpcapCaptor jpcap) {
                t.stop();
 
	}
 
 
	public class ButtonListener implements ActionListener {
 
        @Override
            public void actionPerformed (ActionEvent e){		
		if (e.getSource()==btnStart)
		{
                    //JOptionPane.showMessageDialog(null, "Packet sniffer started");
                    try{
                        final NetworkInterface[] devices = JpcapCaptor.getDeviceList();
			for(int i=0;i<devices.length;i++){
                            NetworkInterface nc=devices[i];
                        jpcap = JpcapCaptor.openDevice(nc, 2000, true, 20);
 
                        startCapThread(jpcap);
 
                        System.out.println("¿ªÊ¼×¥È¡µÚ"+i+"¸ö¿¨¿ÚÉϵÄÊý¾Ý");
			}
                        }catch(Exception ef){
			ef.printStackTrace();
			System.out.println("Æô¶¯Ê§°Ü:  "+ef);
                    }             
 
        	}
		if (e.getSource()==btnStop)
		{              
                    stopthread(jpcap);
                   // JOptionPane.showMessageDialog(null, "Packet sniffer stopped");
                    System.out.println("STOPPED");   
		}
		if (e.getSource()==btnExit)
		{
                    System.exit(0);
		}
 
            }
	}  
 
}

 class TestPacketReceiver  implements PacketReceiver {
	  public String s;       
 
	  public void receivePacket(Packet packet) {
				 //Tcp, java Socket
 
		  		if(packet instanceof jpcap.packet.TCPPacket){
					TCPPacket p=(TCPPacket)packet;
                                s="TCPPacket:| dst_ip "+p.dst_ip+":"+p.dst_port
                                +"|src_ip "+p.src_ip+":"+p.src_port
                                +" |len: "+p.len+" |flag: "+p.d_flag+" |ack_num: "+p.ack;
				System.out.println(s);
 
 
				}
				//UDP, tcp+udp
				else if(packet instanceof jpcap.packet.UDPPacket){
					UDPPacket p=(UDPPacket)packet;
					s="UDPPacket:| dst_ip "+p.dst_ip+":"+p.dst_port
			         +"|src_ip "+p.src_ip+":"+p.src_port
		            +" |len: "+p.len+" |THIS: "+p.d_flag;
		           System.out.println(s);
 
				}
				//ping, ICMPPacket
		       else if(packet instanceof jpcap.packet.ICMPPacket){
		    	   ICMPPacket p=(ICMPPacket)packet;
		    	   //ICMP
		    	   String router_ip="";
		    	   for(int i=0;i<p.router_ip.length;i++){
		    		   router_ip+=" "+p.router_ip[i].getHostAddress();
		    	   }
					s="@ @ @ ICMPPacket:| router_ip "+router_ip
					 +" |redir_ip: "+p.redir_ip
					 +" |mtu: "+p.mtu
		             +" |length: "+p.len+ " |This ICMP: "+p.addr_num;
		          System.out.println(s);
 
				}
 
		       else if(packet instanceof jpcap.packet.ARPPacket){
		    	   ARPPacket p=(ARPPacket)packet;
		    	   //Returns the hardware address (MAC address) of the sender
		    	   Object  saa=   p.getSenderHardwareAddress();
		    	   Object  taa=p.getTargetHardwareAddress();
		    	   s="* * * ARPPacket:| SenderHardwareAddress "+saa
			         +"|TargetHardwareAddress "+taa
		             +" |len: "+p.len;
		         System.out.println(s);
 
				}
 
		     DatalinkPacket datalink  =packet.datalink;
 
		     if(datalink instanceof jpcap.packet.EthernetPacket){
		    	 EthernetPacket ep=(EthernetPacket)datalink;
		    	  s="  datalink layer packet: "
		    		  +"|DestinationAddress: "+ep.getDestinationAddress()
		    		  +"|SourceAddress: "+ep.getSourceAddress();
		    	  System.out.println(s);
 
			}	 
		  }
}

[Norm]

In the thread add code to test a variable and exit if it is set.

Please edit your code and wrap it in code tags. Use the #icon above input box.
Or see: BB Code List - Java Programming Forums

[adilet23]

OK. thank you!

[Fragle]

If you are going to use your own variable to indicate a request to stop then don't forget to make the variable 'volative' other wise the thread code may not see the changes made to it from other threads.

Another robust approach is to use the interrupted flag. So within the thread code you would check the interrupted flag and return if set.

if (Thread.interrupted()) {
   return
}

or maybe you want to keep doing something in a loop which you could aproach like this

class InterruptableRunnable implements Runnable {
 while(!Thread.interrupted) {
      // do work in a loop
 } 
}

Then in in another thread, such as you GUI thread your code can stop the thread like this

thread.interrupt();

Another advantage of using the interrupted flag is that code serveral calls deeper from the runnable code can signal a request to be interrupted in a standard way, for example when performing some IO blocking operation

   try {
        socket.read();
  } catch (InterruptedException) {
      Thread.currentThread().interrupt();
}

Hope that helps