ptr - Necesita realizar una búsqueda DNS inversa de una dirección IP particular en Java

reverse resolve

Question

Necesito obtener la dirección DNS, por ejemplo "http://stackoverflow.com/questions/ask" . Usé el siguiente código y pude obtener la forma de 192.XXX

 Hashtable env = new Hashtable();
env.put(Context.INITIAL_CONTEXT_FACTORY, "com.sun.jndi.dns.DnsContextFactory");
DirContext ictx = new InitialDirContext(env);
String dnsServers = (String) ictx.getEnvironment().get("java.naming.provider.url");
System.out.println("DNS Servers: " + dnsServers ); 

Answer 1

InetAddress ia = InetAddress.getByAddress(new byte[] {74,125,127,106});
// or
ia = InetAddress.getByName("74.125.127.106");
System.out.println(ia.getCanonicalHostName());

Answer 2

Tomé el código vinculado por @Sam DeHaan, lo limpié un poco y lo probé.

/**
* Do a reverse DNS lookup to find the host name associated with an IP address. Gets results more often than
* {@link java.net.InetAddress#getCanonicalHostName()}, but also tries the Inet implementation if reverse DNS does
* not work.
*
* Based on code found at http://www.codingforums.com/showpost.php?p=892349&postcount=5
*
* @param ip The IP address to look up
* @return The host name, if one could be found, or the IP address
*/
private static String getHostName(final String ip)
{
String retVal = null;
final String[] bytes = ip.split("//.");
if (bytes.length == 4)
{
try
{
final java.util.Hashtable<String, String> env = new java.util.Hashtable<String, String>();
env.put("java.naming.factory.initial", "com.sun.jndi.dns.DnsContextFactory");
final javax.naming.directory.DirContext ctx = new javax.naming.directory.InitialDirContext(env);
final String reverseDnsDomain = bytes[3] + "." + bytes[2] + "." + bytes[1] + "." + bytes[0] + ".in-addr.arpa";
final javax.naming.directory.Attributes attrs = ctx.getAttributes(reverseDnsDomain, new String[]
{
"PTR",
});
for (final javax.naming.NamingEnumeration<? extends javax.naming.directory.Attribute> ae = attrs.getAll(); ae.hasMoreElements();)
{
final javax.naming.directory.Attribute attr = ae.next();
final String attrId = attr.getID();
for (final java.util.Enumeration<?> vals = attr.getAll(); vals.hasMoreElements();)
{
String value = vals.nextElement().toString();
// System.out.println(attrId + ": " + value);
if ("PTR".equals(attrId))
{
final int len = value.length();
if (value.charAt(len - 1) == ''.'')
{
// Strip out trailing period
value = value.substring(0, len - 1);
}
retVal = value;
}
}
}
ctx.close();
}
catch (final javax.naming.NamingException e)
{
// No reverse DNS that we could find, try with InetAddress
System.out.print(""); // NO-OP
}
}
if (null == retVal)
{
try
{
retVal = java.net.InetAddress.getByName(ip).getCanonicalHostName();
}
catch (final java.net.UnknownHostException e1)
{
retVal = ip;
}
}
return retVal;
}

Answer 3

Pregunta similar de CodingForums : consulta la publicación n. ° 5 (EXENCIÓN DE RESPONSABILIDAD: El código no es mío, no lo he probado)

Código de origen vinculado:

/**
* 25 Nov 2009 REVERSE DNS LOOKUP USING JNDI
* In this example the IP being looked up is 211.21.152.4
* The octets are reversed (4.152.21.211)
* and appended to the in-addr.arpa zone:
* 4.152.21.211.in-addr.arpa
*/
import javax.naming.*;
import javax.naming.directory.*;
import java.util.*;
public class dns {
public static void main(String[] args) {
try {
Hashtable env = new Hashtable();
env.put("java.naming.factory.initial","com.sun.jndi.dns.DnsContextFactory");
DirContext ctx = new InitialDirContext(env);
Attributes attrs = ctx.getAttributes("4.152.21.211.in-addr.arpa",new String[] {"PTR"});
for (NamingEnumeration ae = attrs.getAll();ae.hasMoreElements();) {
Attribute attr = (Attribute)ae.next();
String attrId = attr.getID();
for (Enumeration vals = attr.getAll();vals.hasMoreElements();
System.out.println(attrId + ": " + vals.nextElement()));
}
ctx.close();
}
catch(Exception e) {
System.out.println("NO REVERSE DNS");
}
}
}