DNS lookup in DNS for SRV records

In the java code below, I am looking for DNS SRV records to resolve the name of the target domain and its associated port for the given domain name, such as root@1000000000.blubluzone.com. The search function specified in / HERE / below returns null somehow, and I cannot get the result of the query (i.e., the array of records is NULL). As a result, a null pointer exception is thrown when an array of records is accessed in a for loop.

What do you think I'm missing to make the following code. I am using dnsjava, and the corresponding jar API file is available at http://www.dnsjava.org/download/ (at the bottom of the page). Thank you in advance for your suggestion.

     import org.xbill.DNS.Lookup;
     import org.xbill.DNS.Record;
     import org.xbill.DNS.SRVRecord;
     import org.xbill.DNS.TextParseException;
     import org.xbill.DNS.Type;

     public class DNSLookup {

        public static void main(String[] args) {

          if (args.length < 1) {
             System.err.println("Usage: java -jar DNSLookup <hostname>");
             System.exit(1);
          }

          String query = "_ssh._tcp." + args[0];

          try {
            /*****HERE*********/
            Record[] records = new Lookup(query, Type.SRV).run();

            for (Record record : records) {
                 SRVRecord srv = (SRVRecord) record;

            String hostname = srv.getTarget().toString().replaceFirst("\\.$", "");
            int port = srv.getPort();

            System.out.println(hostname + ":" + port);
          }
          } catch (TextParseException e) {
             e.printStackTrace();
          }
       }
      }