Finding LDAP server names by DNS lookup.

Question

Hi,
I'm very new with JNDI and DNS
We are hardcoding the ldap server name in our configuration to connect to the Active directory, but the requirement is to know the ldap server name dynmaically by querying the DNS server.
The input given to us are below.
Dns domain : indbank.is.
SRV RRecord : ldap.tcp.
Query dns : ldap.tcp.indbank.is.
The domain controller should be found by a DNS lookup for the domain, then a DNS for Domain controllers that advertise the service, then try to see if the domain controllers areanswering, and if so choose the one with the fastest answer time (to avoid choosing a domain controller over WAN).
Kindly help me.I am beginner and some code sample and tip will be welcome. :)
Thanks in advance.
Hiubert

Answer 1

Thanks a lot to All.
My code is as follows...
import javax.naming.*;
import javax.naming.directory.*;
import java.util.*;
public class dns1
     public static void main(String[] args)     {
          try {
               Hashtable env = new Hashtable();
               env.put("java.naming.factory.initial","com.sun.jndi.dns.DnsContextFactory");
               env.put("java.naming.provider.url", "dns://indbank.is");
               DirContext ctx = new InitialDirContext(env);
               System.out.println("Intial context created...");
               Attributes attrs = ctx.getAttributes("_ldap._tcp.indbank.is",new String[] {"SRV"});
               System.out.println("Attributes are been retrieved...");
               for (NamingEnumeration ae = attrs.getAll();ae.hasMoreElements();)
                    Attribute attr = (Attribute)ae.next();
                    String attrId = attr.getID();
                    System.out.println("Attribute ID retrieved is" + attrId);
                    for (Enumeration vals = attr.getAll();vals.hasMoreElements(); System.out.println(attrId + ": " + vals.nextElement()));
               ctx.close();
          catch(Exception e)
               System.err.println("Problem querying DNS: " + e);
               e.printStackTrace();
The code runs fine and I get the output as follows
0 100 389 ib500ad1.indbank.in
0 100 389 ib500ad2.indbank.in
I have following questions
1) Do these servers which are returned are the domain controllers or the ldap servers.?(or both domaincontrollers and ldap server are same)
2) how to extract the server name alone from this string.
3) If these two server names are domain controllers then how can I query for a DNS for Domain controllers that advertise the service, then try to see if the domain controllers are answering, and if so choose the one with the fastest answer time (to avoid choosing a domain controller over WAN).
Thanks in advance.
-Hiubert