Problem accessing application through a gateway

[Mauro]

Hi,
I've a communication problem with my .NET web application and I need
some suggestions.
My application is composed of few ASP.NET pages running on a Windows
2003
Enterprise Server (.NET 1.1).
When I access these pages from a browser (Explorer 6.x) in my
enterprise LAN
all works right.

When access these pages from an external PC (this means through a
gateway and a firewall) in some cases the browser returns something
like an "Host not found error".

Note that to avoid problems with "natted" addresses I have set the
"natted" name of the server in the host file of the client PC.

The symptoms of the problem are these:
- when I access the first page all works fine
- when I access the second page and submit it (using the standard .NET
postback mechanism) I get an error like "DNS could not locate the
host".

Using a sniffer on the server and on the client I can see that:
- The client correctly sends all the post content on some IP datagrams
- The server seems not to receive all the data: the information about
__EVENTTARGET, __EVENTARGUMENT and __STATEVIEW are lost; I don't
understand if only these pieces of information are lost or if is
missed the entire IP datagram(s) containing them.
On the server this sequence of datagrams seems not to be treated as an
HTTP request (IIS doesn't trace anything about this request) and the
sniffer on the client traps an HTTP 100 message coming from the server
(a continue request).

Note that using a browser on the LAN the server receives all POST data
(included __EVENTTARGET, __EVENTARGUMENT and __STATEVIEW).

I don't understand if the problem is the firewall, the gateway, some
router (fragmentation problem) or something else.

Any ideas?

TIA
Mauro

 

[Konrad Rotuski]

Some firewalls filter not only ports you can connect to,
but also content of datagrams, maybe in your case firewall
filtered html content ?

it seems that it is problems with dns names, maybe try
telnet thatserver 80
then :
GET / HTTP/1.0<enter>
<enter>

and see what data is sent to client in both cases

maybe you should use something like http sniffer to see
all communication inboth cases