private static String getHostName(final String ip) {
        String retVal = null;
// System.out.println(ip);
        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)) {
// System.out.println(value);
                            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;
    }