org.jivesoftware.smack.util.DNSUtil Maven / Gradle / Ivy
/**
* $Revision: 1456 $
* $Date: 2005-06-01 22:04:54 -0700 (Wed, 01 Jun 2005) $
*
* Copyright 2003-2005 Jive Software.
*
* All rights reserved. Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.jivesoftware.smack.util;
import javax.naming.directory.Attributes;
import javax.naming.directory.DirContext;
import javax.naming.directory.InitialDirContext;
import java.util.Hashtable;
import java.util.Map;
/**
* Utilty class to perform DNS lookups for XMPP services.
*
* @author Matt Tucker
*/
public class DNSUtil {
/**
* Create a cache to hold the 100 most recently accessed DNS lookups for a period of
* 10 minutes.
*/
private static Map cache = new Cache(100, 1000*60*10);
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) {
// Ignore.
}
}
/**
* Returns the host name and port that the specified XMPP server can be
* reached at for client-to-server communication. A DNS lookup for a SRV
* record in the form "_xmpp-client._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 default port
* of 5222.
*
* 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 resolveXMPPDomain(String domain) {
if (context == null) {
return new HostAddress(domain, 5222);
}
String key = "c" + domain;
// Return item from cache if it exists.
if (cache.containsKey(key)) {
HostAddress address = (HostAddress)cache.get(key);
if (address != null) {
return address;
}
}
String host = domain;
int port = 5222;
try {
Attributes dnsLookup =
context.getAttributes("_xmpp-client._tcp." + domain, new String[]{"SRV"});
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) {
// Ignore.
}
// Host entries in DNS should end with a ".".
if (host.endsWith(".")) {
host = host.substring(0, host.length()-1);
}
HostAddress address = new HostAddress(host, port);
// Add item to cache.
cache.put(key, address);
return address;
}
/**
* Returns the host name and port that the specified XMPP server can be
* reached at for server-to-server 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 default port
* of 5269.
*
* 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) {
if (context == null) {
return new HostAddress(domain, 5269);
}
String key = "s" + domain;
// Return item from cache if it exists.
if (cache.containsKey(key)) {
HostAddress address = (HostAddress)cache.get(key);
if (address != null) {
return address;
}
}
String host = domain;
int port = 5269;
try {
Attributes dnsLookup =
context.getAttributes("_xmpp-server._tcp." + domain, new String[]{"SRV"});
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._tcp." + domain, new String[]{"SRV"});
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) {
// Ignore.
}
}
// Host entries in DNS should end with a ".".
if (host.endsWith(".")) {
host = host.substring(0, host.length()-1);
}
HostAddress address = new HostAddress(host, port);
// Add item to cache.
cache.put(key, address);
return address;
}
/**
* 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;
}
public boolean equals(Object o) {
if (this == o) {
return true;
}
if (!(o instanceof HostAddress)) {
return false;
}
final HostAddress address = (HostAddress) o;
if (!host.equals(address.host)) {
return false;
}
return port == address.port;
}
}
}