Accessing method in thread

Question

Hi all,
I've got a multicast sender and reciever working, where I collect IP address's of other PC's who are running my application. I would like to access the list of IP's and allow the user to chose an IP address to connect to using a socket to run another thread using a socket whilst continuing listening to more multicast's :)
I have tested my code and the IP's are definately getting added to the list but my problem is accessing them. Here's my code, along with actual output :)
MulticastListener:
import java.io.*;
import java.net.*;
import java.util.Timer;
import java.util.TimerTask;
import java.util.ArrayList;
class MulticastListener extends Thread
Timer timer;
     public MulticastListener(int seconds)
          timer=new Timer();
          timer.scheduleAtFixedRate(new MulticastListen(), 0, seconds*1000);
     class MulticastListen extends TimerTask
          ArrayList<String> ipAddress=new ArrayList<String>();
          public void run()
               InetAddress group=null;
               int port=0;
               //BufferedReader sa = new BufferedReader(new InputStreamReader(System.in));
               System.out.println("Starting Multicast Listener");
               try
                    group=InetAddress.getByName("239.255.255.255");
                    port=20000;
               catch (Exception ex)
                    System.out.println("Usage: multicast_address port");
               //System.out.println("Creating Multicast socket");
               MulticastSocket ms=null;
               InetAddress is=null;
               try
                    is=InetAddress.getLocalHost();
               catch (Exception ex)
                    System.out.println(ex);
               String ip="/"+is.getHostAddress();
               System.out.println("local ip is " +ip);
               try
                    ms=new MulticastSocket(port);
                    ms.joinGroup(group);
                    byte [] buffer=new byte[2];
                    System.out.println("setting up datagram packet");
                    while (true)
                         DatagramPacket dp=new DatagramPacket(buffer,buffer.length);
                         ms.receive(dp);
                         System.out.println("received" + dp.getAddress());
                         InetAddress dpAddress=dp.getAddress();
                         String strAddress=dpAddress.toString();
                         if (!(strAddress.equalsIgnoreCase(ip)))
                              if (!(ipAddress.contains(strAddress)))
                                   ipAddress.add(dp.getAddress().toString());     
                         String [] ipAddressArray=(String[])ipAddress.toArray(new String[ipAddress.size()]);
                         for (int i=0;i<ipAddressArray.length;i++)
                              System.out.println(ipAddressArray);
                         System.out.println("Press Y");
                         //if ((sa.readLine().equalsIgnoreCase("Y")||(sa.readLine().equalsIgnoreCase("y"))))
                         //     System.out.println("yay");
                         //System.out.println("missed");
               catch (IOException ex)
                    System.err.println(ex);
               finally
                    if (ms!=null)
                         try
                              System.out.println("listener closing");
                              ms.leaveGroup(group);
                              ms.close();
                         catch (IOException ex)
          public ArrayList <String> getList()
               return ipAddress;
}MulticastSender:import java.util.Timer;
import java.util.TimerTask;
import java.io.*;
import java.net.*;
public class MulticastSender extends Thread
     Timer timer;
     InetAddress ipAddr=null;
     String ipAddress=null;
     public MulticastSender(int seconds)
          timer=new Timer();
          timer.scheduleAtFixedRate(new MulticastSend(),0,seconds*1000);
     class MulticastSend extends TimerTask
          public void run()
               InetAddress ia=null;
               int port=0;
               byte ttl=(byte)1;
               System.out.println("Starting multicast sender");
               try
                    ia=InetAddress.getByName("239.255.255.255");
                    port=20000;
               catch (Exception ex)
                    System.err.println(ex);
                    System.err.println("Usage: multicast_address port");
               byte [] data="S".getBytes();
               DatagramPacket dp=new DatagramPacket(data,data.length,ia,port);
/*               try
                    MulticastSocket ms=new MulticastSocket();
                    ms.joinGroup(ia);
                    ms.send(dp,ttl);
                    ms.leaveGroup(ia);
                    ms.close();
               catch (SocketException ex)
                    System.err.println(ex);
               catch (IOException ex)
                    System.err.println(ex);
               data="GameRequest".getBytes();
               dp=new DatagramPacket(data,data.length,ia,port);
               System.out.println("Sending message to multicast reciever server:"+ data);
               try
                    System.out.println("sneding messenge");
                    MulticastSocket ms=new MulticastSocket();
                    ms.joinGroup(ia);
                    ms.setBroadcast(true);
                    ms.send(dp,ttl);
                    ms.leaveGroup(ia);
                    ms.close();
                    System.out.println("out");
               catch (SocketException ex)
                    System.err.println(ex);
               catch (IOException ex)
                    System.err.println(ex);
}Main:class Main
     public static void main (String [] args)
          MulticastListener ML=new MulticastListener(10);
          MulticastSender MS=new MulticastSender(10);
          ML.start();
          MS.start();
Actual output:Starting Multicast Listener
Starting multicast sender
sneding messenge
out
local ip is /192.168.1.101
setting up datagram packet
received/192.168.1.102
/192.168.1.102
Press Y
Starting multicast sender
sneding messenge
out
received/192.168.1.101
/192.168.1.102
Press Y
received/192.168.1.102
/192.168.1.102
Press Y
Starting multicast sender
sneding messenge
out
received/192.168.1.101
/192.168.1.102
Press Y
received/192.168.1.102
/192.168.1.102
Press YCheers,
Ben                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   

Answer 1

Hi,
If I understand you correctly, you have a list which your timer listen each time through multicast listener
ArrayList<String> ipAddress=new ArrayList<String>();
The above list changes and it contains IP addresses which are other PCs using your applciation.
The user will come and look at the list and pick up an IP address from the list and open a socket connection with the hostname
I have refactord the code to be
class MulticastListener extends TimerTask
  Timer timer;
  List<String> ipAddress;
     public MulticastListener(int seconds)
          timer=new Timer();
           ipAddress=new ArrayList<String>();
          timer.scheduleAtFixedRate(this, 0, seconds*1000);
      public void run()
//   ..etc..... simlilar to the Sender class
/ / and the main is
class Main
     public static void main (String [] args)
          MulticastListener ML=new MulticastListener(10);
          MulticastSender MS=new MulticastSender(10);
          List<String> ips = ML.getList();
          // get the list
          Foo foo = new Foo("ip");
          Thread t = new Thread(foo,"Foo");
          t.start();
static class Foo implements Runnable {
       private String ip;
       public Foo(String ip) {
            this.ip = ip;
       public void run() {
            // you have the ip
            // open the socket here
}It is just an idea which is reflected through the code, Please let me know if I missed any point
Regards,
Alan Mehio
London, UK