Java getting my IP address

Question

I am trying to get my Internet IP address in Java but I keep getting my local address (ie: 127.0.0.1), when my IP address is 192.168.0.xxx

I am using the line:

Answer 1

Here is my approach to get the IP address.

1. Get your default gateway address
2. Get all the address in your PC
3. Now in your IP(suppose 192.168.100.4) and default gateway IP(suppose 192.168.100.1) have first 9 digit of address must be same, so whichever IP who full this criteria is your IP.

Please see below for full working code.

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.InetAddress;
import java.net.NetworkInterface;
import java.net.SocketException;
import java.util.Enumeration;
import java.util.Iterator;
import java.util.StringTokenizer;
import java.util.TreeSet;

public class MyIpAddress {

    public static void main(String[] args) {
        // doPortForwarding();

        MyIpAddress myIpAddress = new MyIpAddress();

        // get default address
        String yourIp = myIpAddress.getYourIp(myIpAddress
                .getDefaultGateWayAddress());
        System.out.println(yourIp);

        // get

    } // amin

    // return ip address for which u need to do port forwarding
    private String getYourIp(String defaultAddress) {

        String temp = defaultAddress.substring(0, 11);
        String ipToForward = "";

        TreeSet ipAddrs = getIpAddressList();
        for (Iterator iterator = ipAddrs.iterator(); iterator.hasNext();) {

            String tempIp = iterator.next();
            if (tempIp.contains(temp)) {
                ipToForward = tempIp;
                break;
            }
        }

        return ipToForward;

    }// ipForPortForwarding

    // get the ipaddress list
    private TreeSet getIpAddressList() {
        TreeSet ipAddrs = new TreeSet();

        try {
            Enumeration interfaces = NetworkInterface
                    .getNetworkInterfaces();
            while (interfaces.hasMoreElements()) {
                NetworkInterface iface = interfaces.nextElement();
                // filters out 127.0.0.1 and inactive interfaces
                if (iface.isLoopback() || !iface.isUp())
                    continue;

                Enumeration addresses = iface.getInetAddresses();
                while (addresses.hasMoreElements()) {

                    InetAddress addr = addresses.nextElement();

                    ipAddrs.add(addr.getHostAddress());

                }// 2 nd while
            }// 1 st while
        } catch (SocketException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

        return ipAddrs;

    }// getIpAddressList

    // get default gateway address in java

    private String getDefaultGateWayAddress() {
        String defaultAddress = "";
        try {
            Process result = Runtime.getRuntime().exec("netstat -rn");

            BufferedReader output = new BufferedReader(new InputStreamReader(
                    result.getInputStream()));

            String line = output.readLine();
            while (line != null) {
                if (line.contains("0.0.0.0")) {

                    StringTokenizer stringTokenizer = new StringTokenizer(line);
                    stringTokenizer.nextElement();// first string is 0.0.0.0
                    stringTokenizer.nextElement();// second string is 0.0.0.0
                    defaultAddress = (String) stringTokenizer.nextElement(); // this is our default address
                    break;
                }

                line = output.readLine();

            }// while
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

        return defaultAddress;

    }// getDefaultAddress
}