src/main/java/com/juick/xmpp/s2s/DNSQueries.java


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package com.juick.xmpp.s2s;

import java.net.UnknownHostException;
import java.util.Hashtable;
import java.util.Random;
import javax.naming.NamingException;
import javax.naming.directory.Attribute;
import javax.naming.directory.DirContext;
import javax.naming.directory.InitialDirContext;

/**
 *
 * @author ugnich
 */
public class DNSQueries {

    private static Random rand = new Random();

    public static HostnamePort getServerAddress(String hostname) throws UnknownHostException {

        String host = hostname;
        int port = 5269;

        try {
            Hashtable<String, String> env = new Hashtable<String, String>(5);
            env.put("java.naming.factory.initial", "com.sun.jndi.dns.DnsContextFactory");
            DirContext ctx = new InitialDirContext(env);
            Attribute att = ctx.getAttributes("_xmpp-server._tcp." + hostname, new String[]{"SRV"}).get("SRV");

            if (att != null && att.size() > 0) {
                int i = rand.nextInt(att.size());
                try {
                    String srv[] = att.get(i).toString().split(" ");
                    port = Integer.parseInt(srv[2]);
                    host = srv[3];
                } catch (Exception e) {
                }
            }

            ctx.close();
        } catch (NamingException e) {
        }

        return new HostnamePort(host, port);
    }
}