Querying DNS to find all ActiveDirectory it knows about

DCDiscovery.java

package cz.syntea.common.apmsvr.jtalk2ad;

import java.util.ArrayList;
import java.util.Enumeration;
import java.util.Hashtable;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import javax.naming.Context;
import javax.naming.NamingEnumeration;
import javax.naming.NamingException;
import javax.naming.directory.Attribute;
import javax.naming.directory.Attributes;
import javax.naming.directory.DirContext;
import javax.naming.directory.InitialDirContext;

public class DCDiscovery {

    public static void main(String args[]) {
      String[] dnss = findDNSs();
        for (int i = 0; i < dnss.length; i++) {
            lookUpDC(dnss[i], "syntea.cz");
        }
     // lookUpDC("192.168.56.101", "kec.cz");
    }

    public static void lookUpDC(String dns,String hostname){
        String domainController;
        try {

            DirContext dnsContext = dnsQuery(dns, hostname);
            Attributes dnsQueryResult = dnsContext.getAttributes("_ldap._tcp.dc._msdcs",new String[]{"SRV"});

            if (dnsQueryResult == null) {
                System.out.println("Returned NULL");
            }
            for (NamingEnumeration dnsRR =
                    dnsQueryResult.getAll(); dnsRR.hasMoreElements();) {
                Attribute rr = (Attribute) dnsRR.next();

                //String attrId = rr.getID();
                for (Enumeration vals = rr.getAll(); vals.hasMoreElements();) {
                    Object el = vals.nextElement();
                    domainController = el.toString().split(" ")[3];

                    System.out.println("DomainController: " + domainController+ " found with DNS: "+dns);
                }
            }
            dnsContext.close();
        } catch (Exception e) {
            //System.err.println("Error performing DNS lookup for: " + "dns://"+dns+"/"+hostname + "\n" + e);
            //e.printStackTrace();
        }
    }

    public static String[] findDNSs() {
        try {
            Hashtable dnsEnv = new Hashtable();
            dnsEnv.put("java.naming.factory.initial",
                    "com.sun.jndi.dns.DnsContextFactory");
            dnsEnv.put("java.naming.provider.url", "dns:///");
            DirContext dnsContext = new InitialDirContext(dnsEnv);
            Hashtable retEnv = dnsContext.getEnvironment();
            Object obj = retEnv.get(Context.PROVIDER_URL);
            Pattern ippattr = Pattern.compile("(25[0-5]|2[0-4]\\d|[0-1]?\\d?\\d)(\\.(25[0-5]|2[0-4]\\d|[0-1]?\\d?\\d)){3}");
            Matcher matcher = ippattr.matcher(obj.toString());
            ArrayList<String> iplist = new ArrayList();
            while(matcher.find()){
                iplist.add(matcher.group());
            }
            return iplist.toArray(new String[0]);
        } catch (Exception e) {
        }
        return new String[0];
    }

    public static DirContext dnsQuery(String dns,String hostname) throws NamingException{
        Hashtable dnsEnv = new Hashtable();
            dnsEnv.put("java.naming.factory.initial", "com.sun.jndi.dns.DnsContextFactory");
            //    dnsEnv.put("java.naming.provider.url", "dns://" + dnsNameServer + "/" + aDDomain);
           // dnsEnv.put("java.naming.provider.url", "dns:///_sites.dc._msdcs.syntea.cz");// defaultni dns
            dnsEnv.put("java.naming.provider.url", "dns://"+dns+"/"+hostname);

            return new InitialDirContext(dnsEnv);
    }
}