Name: boT120536 Date: 01/21/2001


java version "1.3.0_01"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.3.0_01)
Java HotSpot(TM) Client VM (build 1.3.0_01, mixed mode)


1. Exact steps to reproduce the problem.
This problem can ONLY be reproduced on a computer with more than one network
card (a modem also considered as being a network card). I use fixed IP-
addresses for my 2 LAN-NIC's (192.168.x.x-range or 10.0.x.x-range). My modem
uses DHCP. This bug cannot be reproduced on a computer with only one NIC or
only a modem. I originally discovered this bug in JDK 1.1.8, but apparently
nobody discovered it until now, so it's still there in Java 1.3.

2. Java SOURCE CODE that demonstrates the problem, if possible.
This little program just downloads a zip-file from a FTP-server (anonymous) to
a local disk.

import java.net.*;
import java.io.*;
public class FtpDownload
{
 public static void main(String[] args)
 {
  try
  {
   URL location = new URL
("ftp://ftp.simtel.net/pub/simtelnet/win95/inet/1cftp780.zip");
   InputStream in = location.openStream();
   OutputStream out = new FileOutputStream("1cftp780.zip");
   int k;
   while ((k = in.read()) != -1) out.write(k);
   out.close();
   in.close();
  }
  catch (Exception e) {}
 }
}

3. Exact text of any error message(s) that appeared.
FtpProtocolException: PORT

4. Any trace information.
I traced the network traffic with a network monitor program. I found an error
in the information which was send by my java-made application. The PORT command
sends an IP-address to the FTP-server. The FTPClient didn't send the IP-address
of my modem to the FTP-server, but the address of one of my NIC's (a local
address... 192.168.0.5).
I looked into the java-source of 'FtpClient.class' and I found out that
in "protected Socket openDataConnection(String s)", the first line is:

InetAddress inetaddress = InetAddress.getLocalHost();

This is not correct! This doesn't work when there are multiple NIC's (with
multiple IP-addresses) installed in a computer. The FtpClient-class inherits
TransferProtocolClient, which inherits from NetworkClient. In NetworkClient
there is a Socket called "serverSocket", which makes the initial contact with
the FTP-server. So the statement should not use InetAddress.getLocalHost(), but
it should be:

InetAddress inetaddress = serverSocket.getLocalAddress();

This determines which IP-address must be send to the server correctly. I tested
it with my modem, which worked fine. I also tested it with a FTP-server on my
local network.

5. Include additional configuration information that you think is relevant to
the problem
Well, you must have more than one IP-address assigned to your computer to
reproduce this bug. I think it can be reproduced on all computers with a NIC
and a modem. It's not reproducable on a computer which routes all IP-packets to
one NIC.
(Review ID: 115292)
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