View Full Version : Karmic bug with JAVA getHostAddress() ?

February 1st, 2010, 10:13 PM

im trying to get the LAN address from Karmic

myIp = InetAddress.getLocalHost();
str = myIp.getHostAddress();

but I only get the local instead of the dhcp address the network manager should have something like 192.168.0.x

getHostAddress() on PC, Mac an another linux distro return the right thing .... is there some bug in karmic.
btw i tried both java package, openJDK and sunJRE with the same result...

so it isn't java, it might be /etc/hosts not being updated ?


February 2nd, 2010, 01:50 AM
I'm not positive what your issue is but I see a couple of possibilities.

1) A system can have several addresses. As an example you could have a local area net connected to the internet, another that is for internal purposes only and you could have a loop back address. All of which are valid addresses for your computer. [I suspect this is not your issue]

2) After reviewing the documentation. I see that INetAddress.getLocalHost() has a note saying:

If there is a security manager, its checkConnect method is called with the local host name and -1 as its arguments to see if the operation is allowed. If the operation is not allowed, an InetAddress representing the loopback address is returned.

You likely have a permissions issue.

February 2nd, 2010, 02:27 AM
TennTux is right; a system can have multiple interfaces, each supporting an IPv4 and IPv6 address.

Here's some code that can be used to get the IP addresses assigned to all interfaces, or from a specific interface.

import java.net.*;
import java.util.*;

public class GetHost
public static void main(String[] args)
Enumeration<NetworkInterface> nis = NetworkInterface.getNetworkInterfaces();

// option 1
while (nis.hasMoreElements())
System.out.println("network interface: " + nis.nextElement().toString());

// option 2 (not recommended)
System.out.println("eth0 interface: " + NetworkInterface.getByName("eth0"));
catch (SocketException e)

I marked option 2 above as "not recommended" because not everyone will have the same interface aliases. Although "eth0" is a common alias used by many distros, it may not be (and I'm sure it's not) used by Windoze.