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Resolving DNS names with DNS.GetHostByAddress

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Jon Gilkison

I'm having quite a bit of trouble getting the System.Net.Dns class
working
in my asp.net application.

Below is the simple line of code causing me grey hairs:

Response.Write("host
name:"+Dns.GetHostByAddress(Dns.GetHostByAddress(Request.UserHostAddress
).HostName);

Hitting this page from the internal network resolves the machine name,
but
hitting this page from the internet, outside of the local network,
results
in the following error:

The requested name is valid and was found in the database, but it does
not
have the correct associated data being resolved for

I'm sure this is a security thing, but I can't figure it out for the
life of
me ... anyone?

Reply to this message...

Sean Bytnar

Try this code:

try
{
    IPHostEntry ipheClient = new IPHostEntry();
    ipheClient =
Dns.GetHostByAddress(HttpContext.Current.Request.UserHostAddress);
    Response.Write("Host Name: " + ipheClient.HostName);
}
catch(Exception ex)
{
    Response.Write("Host Name: Unresolved");
}

Sean

-----Original Message-----
From: Jon Gilkison [mailto:Click here to reveal e-mail address]
Sent: Tuesday, May 21, 2002 5:12 PM
To: aspngsec
Subject: [aspngsec] Resolving DNS names with DNS.GetHostByAddress

I'm having quite a bit of trouble getting the System.Net.Dns class
working in my asp.net application.

Below is the simple line of code causing me grey hairs:

Response.Write("host
name:"+Dns.GetHostByAddress(Dns.GetHostByAddress(Request.UserHostAddress
).HostName);

Hitting this page from the internal network resolves the machine name,
but hitting this page from the internet, outside of the local network,
results in the following error:

The requested name is valid and was found in the database, but it does
not have the correct associated data being resolved for

I'm sure this is a security thing, but I can't figure it out for the
life of me ... anyone?

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Reply to this message...

	System.Net.Dns
	System.Net.IPHostEntry
	System.Web.HttpContext

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