.Net 2.0 & Dns.GetHostEntry

[Joe K]

I am intermitently getting a System.Net.Sockets.SocketException ("No such
host is known") when calling Dns.GetHostEntry(). It doesn't seem to have
any pattern to it, but seems to be occurring on a variety of IP addresses
(e.g. internal addresses such as 192.168.x.x). Anyone else see this? Is
there a known .Net 2.0 bug for this?

Joe

 

[Joe K]

So I verified this fails any time there is a DNS configuration that results
in nslookup returning an error regarding "Non-existent domain." In my case
this is a system that is not part of a domain but is performing an nslookup
on a system that is in a domain. Oddly enough, the deprecated method
Dns.GetHostEntry replaces, Dns.GetByName, works flawlessly. Below you will
find the sample code to reproduce and the nslookup results.

It seems this is a .Net 2.0 bug.


******nslookup results******
nslookup -type=ptr 192.168.100.10
Server: my-dc.mycompany.int
Address: 192.168.100.10

*** my-dc.mycompany.int can't find 192.168.100.10: Non-existent domain



******Sample Code******
using System;
using System.Collections.Generic;
using System.Text;
using System.Net;

namespace TestDns
{
class Program
{
static void Main(string[] args)
{
if (args.Length < 1)
{
Console.WriteLine("TestDns [ip address or hostname]");
return;
}
Console.WriteLine("Test #1");
try
{
Console.WriteLine(Dns.GetHostEntry(args[0]).HostName);
}
catch (Exception ex)
{
Console.WriteLine(ex.Message);
Console.WriteLine(ex.StackTrace);
}
Console.WriteLine("Test #2");
try
{
Console.WriteLine(Dns.GetHostByName(args[0]).HostName);
}
catch (Exception ex)
{
Console.WriteLine(ex.Message);
Console.WriteLine(ex.StackTrace);
}
}
}
}

 

[Peter Duniho]

So I verified this fails any time there is a DNS configuration that
results in nslookup returning an error regarding "Non-existent
domain." In my case this is a system that is not part of a domain
but is performing an nslookup on a system that is in a domain.
Oddly enough, the deprecated method Dns.GetHostEntry replaces,
Dns.GetByName, works flawlessly. Below you will find the sample
code to reproduce and the nslookup results.

It seems this is a .Net 2.0 bug.

I don't know what the problem is, but one person wrote a comment to this
documentation page:
http://msdn2.microsoft.com/en-us/library/ms143998.aspx

....that seems to confirm the problem you're having (though in a slightly
different example, the behavior seems basically the same problem).

I wonder if you or the other person has reported this problem as a bug
yet. I haven't run into it myself, but if you have a reproducible
example, you should probably report it so that it can be fixed.

Pete

 

[Joe K]

Yes, I think I have a reproducible case but it requires a specific DNS
setup. The link you pointed me to sounds exactly like my issue, but I think
the poster didn't realize there is a more specific setup required to
reproduce (e.g. I can run his test case without a problem).

I wasn't planning on reporting it as a bug due to the sheer effort to push
this through Microsoft (e.g. open a case, wait a week for callback, work
through 1st level engineer, wait for engineer to setup & reproduce, wait for
engineer to talk with development, wait for development to acknowledge as a
bug, etc.., etc...). Okay, okay, I am a bit jaded by my last two
experiences in which after all that effort, the product failures we actually
deemed documentation bugs!

If anyone has more details, I'd be interested. In the meantime, I will be
making a critical hotfix to our application that uses the deprecated method
instead of GetHostEntry.

Thanks for reply.

Joe