CODEWITHSUNDEEP
javanetwork-programming
codeomnitrix
codeomnitrix

Reputation: 4249

problem with finding the hostname with ip addr using InetAddress class

I have written the two program 1st whois.java to find the ip address of the given hostname

import java.net.*;
import java.io.*;

public class whois{
    public static void main(String args[]) throws IOException{
        String hostName = args[0];

        try{
            InetAddress ipaddress = InetAddress.getByName(hostName);
            System.out.println("IP address: " + ipaddress.getHostAddress());
        }catch(UnknownHostException e){
            System.out.println("Could not find IP address for: " + hostName);
        }
    }
}

and other whois2.java which finds hostname for given ip

import java.net.*;
import java.io.*;

class whois2{
    public static void main(String args[]){
        try{

            String str[] = args[0].split("\\.");

            byte btArr[] = new byte[]{(byte)Integer.parseInt(str[0]), (byte)Integer.parseInt(str[1]), (byte)Integer.parseInt(str[2]), (byte)Integer.parseInt(str[3])};
            InetAddress ipAddr = InetAddress.getByAddress(btArr);
            System.out.println("Host name for this is : " + ipAddr.getHostName());
        }catch(UnknownHostException e){
            System.out.println("Unable to find the host for ip specified " + args[0]);
        }
    }
}

and then i ran the program with jdk 1.6 and get following outputs:

$java whois google.com

IP address: 209.85.231.104

$java whois2 209.85.231.104

Host name for this is : maa03s01-in-f104.1e100.net

why the host name is different not google.com?

Thanks in advance

Upvotes: 2

Views: 2875

Answers (2)

Joel
Joel

Reputation: 30146

The server responsible, as defined by the DNS lookup, for handling requests to a particular hostname need not have the same hostname as that of the original lookup.

A more typical example would be that requests for foobar.com are handled by a server at an IP, with IP having hostname www.foobar.com.

Note also that the handling server may vary by region.

So I get the same using the linux host tool:

joel@bohr:~$ host google.com 
google.com has address 173.194.37.104

... requests to google.com should be handled by the server at 173.194.37.104

joel@bohr:~$ host 173.194.37.104
104.37.194.173.in-addr.arpa domain name pointer lhr14s02-in-f104.1e100.net.

... the hostname of the server at 173.194.37.104 is lhr14s02-in-f104.1e100.net

joel@bohr:~$ host lhr14s02-in-f104.1e100.net
lhr14s02-in-f104.1e100.net has address 173.194.37.104

... and sanity check, the IP of lhr14s02-in-f104.1e100.net is indeed 173.194.37.104

Upvotes: 2

Andreas Dolk
Andreas Dolk

Reputation: 114757

whois(ip) resolves to the name of the registered server, not to an entry on a domain name server.

Same happens when we use whois services on the web:

http://whois.domaintools.com/google.com resolves to IP 74.125.155.99 (from my location!), http://whois.domaintools.com/74.125.155.99 resolves the host px-in-f99.1e100.net (which again is different from your results)

Upvotes: 1

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