/**
* $RCSfile: DNSUtil.java,v $
* $Revision: 60 $
* $Date: 2007-08-27 16:52:28 +0200 (lun, 27 ago 2007) $
*
* Copyright (C) 2004-2005 Jive Software. All rights reserved.
*
* This software is published under the terms of the Apache License
*/
package com.anzsoft.server.JabberHTTPBind;
import javax.naming.directory.Attributes;
import javax.naming.directory.InitialDirContext;
import javax.naming.directory.DirContext;
import java.util.Hashtable;
/**
* Utilty class to perform DNS lookups for XMPP services.
*
* @author Matt Tucker
*/
public class DNSUtil
{
private static DirContext context;
static
{
try
{
Hashtable env = new Hashtable();
env.put("java.naming.factory.initial", "com.sun.jndi.dns.DnsContextFactory");
context = new InitialDirContext(env);
}
catch (Exception e)
{
e.printStackTrace();
}
}
/**
* Returns the host name and port that the specified XMPP server can be
* reached at for communication. A DNS lookup for a SRV
* record in the form "_xmpp-server._tcp.example.com" is attempted, according
* to section 14.4 of RFC 3920. If that lookup fails, a lookup in the older form
* of "_jabber._tcp.example.com" is attempted since servers that implement an
* older version of the protocol may be listed using that notation. If that
* lookup fails as well, it's assumed that the XMPP server lives at the
* host resolved by a DNS lookup at the specified domain on the specified
* default port.<p>
*
* As an example, a lookup for "example.com" may return "im.example.com:5269".
*
* @param domain the domain.
* @return a HostAddress, which encompasses the hostname and port that the XMPP
* server can be reached at for the specified domain.
*/
public static HostAddress resolveXMPPServerDomain(String domain, int defaultport)
{
if (context == null)
{
return new HostAddress(domain, defaultport);
}
String host = domain;
int port = defaultport;
try
{
Attributes dnsLookup = context.getAttributes("_xmpp-client._tcp." + domain);
String srvRecord = (String)dnsLookup.get("SRV").get();
String [] srvRecordEntries = srvRecord.split(" ");
port = Integer.parseInt(srvRecordEntries[srvRecordEntries.length-2]);
host = srvRecordEntries[srvRecordEntries.length-1];
}
catch (Exception e)
{
// Attempt lookup with older "jabber" name.
try
{
Attributes dnsLookup = context.getAttributes("_jabber-client._tcp." + domain);
String srvRecord = (String)dnsLookup.get("SRV").get();
String [] srvRecordEntries = srvRecord.split(" ");
port = Integer.parseInt(srvRecordEntries[srvRecordEntries.length-2]);
host = srvRecordEntries[srvRecordEntries.length-1];
}
catch (Exception e2)
{ }
}
// Host entries in DNS should end with a ".".
if (host.endsWith("."))
{
host = host.substring(0, host.length()-1);
}
return new HostAddress(host, port);
}
/**
* Encapsulates a hostname and port.
*/
public static class HostAddress
{
private String host;
private int port;
private HostAddress(String host, int port)
{
this.host = host;
this.port = port;
}
/**
* Returns the hostname.
*
* @return the hostname.
*/
public String getHost()
{
return host;
}
/**
* Returns the port.
*
* @return the port.
*/
public int getPort()
{
return port;
}
public String toString()
{
return host + ":" + port;
}
}
}