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clarification about InetAddress class and its mehods

bhagavatula indu sekhar
Ranch Hand

Joined: Sep 17, 2006
Posts: 34
i am expected to get the domain names of servers that are connected to Internet and keep them in a database.

it has been suggested by some members of this forum to make use of InetAddress class.

so just to test and know how to use InetAddress i wrote the following program
the jdk kit i have is jdk6.0

i need some clarifications about the output of the program.



import java.io.*;
import java.net.*;
import javax.swing.*;

public class Inetdemo {

public static void main(String[] args) {
Inetdemo in=new Inetdemo();

}
public Inetdemo(){
String site_name=JOptionPane.showInputDialog("Enter a site name");// accepts input the site name
try{

InetAddress inet=InetAddress.getByName(site_name);
System.out.println("Host name is "+inet.getHostName()+"\nHost Address is "+inet.getHostAddress()+"\nCanonical host name is "+inet.getCanonicalHostName());
}
catch(UnknownHostException ue){
ue.printStackTrace();
System.out.println("HostERROR!");
}
catch(Exception e){
e.printStackTrace();
System.out.print("Exception");
}
}
}


when the input to the program is

a) google.com the output is
Host name is google.com
Host Address is 64.233.187.99
Canonical host name is jc-in-f99.google.com

b) www.google.com the output is
Host name is www.google.com
Host Address is 216.239.37.99
Canonical host name is va-in-f99.google.com

c) 216.239.37.99 the output is
Host name is va-in-f99.google.com
Host Address is 216.239.37.99
Canonical host name is va-in-f99.google.com


doubt 1)
why is the address value is different when the input is google.com from that of www.google.com?

doubt 2)
what is the difference between getCanonicalHostName() and getHostName() methods?
Joe Ess
Bartender

Joined: Oct 29, 2001
Posts: 8971
    
    9


public String getHostName()
Gets the host name for this IP address.

If this InetAddress was created with a host name, this host name will be remembered and returned; otherwise, a reverse name lookup will be performed and the result will be returned based on the system configured name lookup service. If a lookup of the name service is required, call getCanonicalHostName.

java.net.InetAddress


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subject: clarification about InetAddress class and its mehods