Reverse DNS Lookups

[J. M. M. I. <ma...@mo...>]

Hi,
    I'm trying to work on some spam filtering software that uses dnsjava to
do reverse DNS lookups using specific DNS servers.  Specifically, i'm using
DNS Realtime Blackhole Lists (DNSRBL's).  Basically, the idea is that given
a server, "permblock.easynet.net" -- and an ip address you want to check
against that server's "known spammers list" (in this case, 69.1.80.67-- you
do a lookup of "67.80.1.69.permblock.easynet.net."

Some DNS servers this works with, others it doesnt.  basically, any dns
server i can't ping doesnt work.  I get an "UnknownHostException" thrown
when i create a resolver.

Anyway, I'm wondering if there's a way around this that i'm not
understanding, or if there's some limitation there, or if maybe i'm totally
off base here.

Thanks for any help in advance,
    Matt Miller

Code is as follows:

----------------------------

/*
 * TestDNS.java
 *
 * Created on May 22, 2003, 2:03 PM
 */
import org.xbill.DNS.*;
import java.net.*;
import java.io.*;
/**
 *
 * @author  matt
 */
public class TestDNS {

    /** Creates a new instance of TestDNS */
    public TestDNS() {
    }
    public static void main(String args[]) {
        try {
            String[] dnslist = new String[1];
            dnslist[0] = "permblock.easynet.net";
            Resolver resolver = null;
            try {
                resolver = new ExtendedResolver(dnslist);
            } catch (UnknownHostException ee) {
                ee.printStackTrace();
            }
            Name name = null;
            try {
                name = Name.fromString("67.80.1.69.permblock.easynet.net.");
            } catch (Exception e) {
                e.printStackTrace();
            }
            Record question = Record.newRecord(name, Type.A, DClass.IN);
            Message query = Message.newQuery(question);
            Message response = null;
            try {
                response = resolver.send(query);
            }
            catch (IOException e) {
                // A network error occurred.  Press on.
                e.printStackTrace();
                System.exit(0);
            }
            short rcode = response.getHeader().getRcode();
            System.out.println("RCODE = " + rcode);
        } catch (Exception e) {
            e.printStackTrace();
        }

    }

}