On the JDK1.1.x release the method InetAddress.getHostName() does not return a fully qualified host when running on the NT platform. The following sample of code demonstrates this problem.



import java.net.*;

class Test {
  static void println (Object x) { System.out.println(x); }
  public static void main (String argv[]) {
    testit("(put in a local host name here)"); // substitute a local machine name here
    testit("www.yahoo.com"); // obviously not on local net
    println("\ngetLocalHost testing:");
    try {
      // InetAddress a = java.net.InetAddress.getByName("206.26.48.100");
      InetAddress a = java.net.InetAddress.getLocalHost();
      println("a = Inetaddress.getLocalHost = " + a);
      println("a.getHostName() = " + a.getHostName());
      println("a.getHostAddress() = " + a.getHostAddress());
      //println("a.getHostAddress() = " + a.getHostAddress());
    } catch (Exception e) {
      System.err.println("Lost: " + e);
    }
  }

  static void testit(String hostname) {
    try {
      println("\nTesting " + hostname);
      URL u = new URL("http://" + hostname);
      println("URL U = " + u);
      println("u.getHost() = " + u.getHost());
      println("InetAddress.getByName(u.getHost())) = " + InetAddress.getByName(u.getHost()));
    } catch (Exception e) {
      System.err.println("Lost " + e);
    }
  }
}

On the Solaris platform when dns is enabled everything works fine. On NT 4.0 even when DNS is enabled getHostName() return the short host name. This is not a duplicate of bug ids 4109291 and 4069806.

Name: yyT116575 Date: 01/08/2001


java version "1.3.0"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.3.0-C)
Java HotSpot(TM) Client VM (build 1.3.0-C, mixed mode)


I was attempting to use Java to analyze web server logs in which the client IP
addresses were recorded but reverse DNS info was not captured. I was able to
translate most translatable IP addresses by obtaining an InetAddress object and
asking it for the translation. However, some addresses I knew to be
translatable were not translated.

Here is a demo:

import java.net.InetAddress;

class Reverse
{
    public static void main(String[] args)
    {
        for (int x=0; x<args.length; ++x) {
            String ip = args[x];
            InetAddress addr;
            try {
                addr = InetAddress.getByName(ip);
            }
            catch(Exception e) {
                System.out.println(ip + " got " + e);
                continue;
            }
            System.out.println(ip + " => " + addr.getHostName());
        }
    }
}

Here is an equivalent Perl program:

use Socket;
for (@ARGV) {
$hostname = pack('C4', split('\.'));
$hostname = gethostbyaddr($hostname, AF_INET) || $_;
print "$_ => $hostname\n";
}

And here is output from both programs on my system (DNS server at 38.9.211.2):

Using Java ...
204.160.241.71 => developer.java.sun.com
152.140.27.250 => 152.140.27.250
12.38.117.9 => 12.38.117.9
216.65.106.130 => 216.65.106.130
207.46.230.218 => microsoft.com
12.34.56.78 => 12.34.56.78

Using Perl ...
204.160.241.71 => developer.java.sun.com
152.140.27.250 => user.mcd.com
12.38.117.9 => tep1-bos.Scient.COM
216.65.106.130 => host130.the-cloak.com
207.46.230.218 => microsoft.com
12.34.56.78 => 12.34.56.78

InetAddress handled arguments 0, 4, and 5 correctly. It failed on 1, 2, and 3.

The only unusual thing about the problem addresses that I can see is that a
forward lookup on the reverse output fails. You can't ping user.mcd.com, for
instance. But, while the machine names are bogus, they are nevertheless
informative to an analyst (the claimed domains checked out ok at arin.net).
The first two machines (user.mcd.com and tep1-bos-Scient.COM) are apparently
corporate firewalls, and the third is some sort of anonymizer service.

I also tried calling the gethostbyaddr function on the problem addresses from a
C program. The returned HOSTENT structure looked fine and contained the
desired machine names.
(Review ID: 114658)
======================================================================