Determining IP address of localhost (Problem)

Question

The below code outputs this on my Windows XP machine:
main Local IP Address : 192.168.1.100
main Local hostname : equus
alt Local IP Address : 127.0.0.1
alt Local hostname : localhost
That is all correct, and then I run the same code on my RH9 linux box and I get this:
main Local IP Address : 127.0.0.1
main Local hostname : proliant
Any ideas why it isn't getting the local IP address that it should be?
import java.net.*;
public class WhoAmI {
     //Tells you the domain name and IP of the machine you are running.
     public static void main(String[] args) {
          try {
               InetAddress localaddr = InetAddress.getLocalHost();
               System.out.println(
                    "main Local IP Address : " + localaddr.getHostAddress());
               System.out.println(
                    "main Local hostname : " + localaddr.getHostName());
               System.out.println();
               InetAddress[] localaddrs = InetAddress.getAllByName("localhost");
               for (int i = 0; i < localaddrs.length; i++) {
                    if (!localaddrs.equals(localaddr)) {
                         System.out.println(
                              "alt Local IP Address : "
                                   + localaddrs[i].getHostAddress());
                         System.out.println(
                              "alt Local hostname : "
                                   + localaddrs[i].getHostName());
                         System.out.println();
          } catch (UnknownHostException e) {
               System.err.println("Can't detect localhost : " + e);

Answer 1

if I had one running on a different LAN
and multicast it to the internet and the other picked
it up I wonder what the DatagramPacket sender IP would
be marked as? The WAN address of that specific senders
LAN with some sort of additional info to specify that
particular PC in the LAN?Very good question. I'm assuming that you mean that the LANs are connected to the Internet via a router that does network address translation (eg, a Linksys router on a home network)?
If that's the case, then the packet you receive would have the WAN address of the router. And to send packets back, you'd have to configure the router to pass through UDP packets on the particular port to the desired destination host.
Ugly, no?