Compiled Web App Unavailable to Some Users

[Guest]

Hello Everyone:

I am having the most bizarre problem with my asp.net web app...this is my
first web app in asp.net and I inherited it from a programmer who quit...so,
I am not completely familiar with all the ins and outs.

The problem is that some machines can open my web app and some machines
cannot...In fact, the server, which is hosting the app and has VS.Net
installed, cannot access the app via the external IP address, but other
machines can...weird, huh?

I tried pinging the IP from the server and that worked...telnet failed.

I've tried removing the Windows Security and that didn't help.

I tried including the port number in the IP Address in my browser and that
failed.

I checked IIS and it is running (which, I guess is obvious b/c some users
are able to see the app).

I verified that the port 80 is open (which, again, is obvious).

I messed with different browsers (Firefox and Netscape) and still can't log
in.

The error message I'm getting is "this page cannot be displayed"...I tried
turning off Friendly HTTP error messages and still get the ambiguous message.

Not sure where to start on this...I've put in about 20 hours (which is to be
expected, considering I'm new)...but, I'm close to my wits end.

Is there a way to trap the error?...Has anyone ran into this
before?...Anyone have an idea?

Thanks!!!

 

[bruce barker]

you should use a network sniffer to check if you can connect. if you
don't have one, first use telnet specifying to connect on port 80. if
telnet can not connect you have a network problem (either router or
proxy). if you can connect type:

GET /default.aspx HTTP/1.1

the server shoudl respond.


-- bruce (sqlwork.com)

 

[Larry Bud]

I am having the most bizarre problem with my asp.net web app...this is my

first web app in asp.net and I inherited it from a programmer who quit...so,
I am not completely familiar with all the ins and outs.

The problem is that some machines can open my web app and some machines
cannot...In fact, the server, which is hosting the app and has VS.Net
installed, cannot access the app via the external IP address, but other
machines can...weird, huh?

Let's start from the beginning. The server that you're trying to hit,
it's through the internet?

The machines that are having the problem, are they in your company, on
the same subnet? Do they resolve the address the same?

 

[Juan T. Llibre]

1. Can you see localhost ?

Try this link : http://localhost/

Does it work ?

2. Does the server have an external domain name ?

Try editing your HOSTS file with Notepad
( Drive:\WINDOWS\system32\drivers\etc\hosts )

Put this entry in your server's HOSTS file :

127.0.0.1 www.yourdomain.com

Save hosts ( no extension on the file... make sure there's no .txt extension ) and run

http://www.yourdomain.com/ in your browser.

Can you see it ?

 

[Juan T. Llibre]

re:

if telnet can not connect you have a network problem (either router or proxy)

Hi, Bruce.

The problem might be as simple as the network using NAT addressing.
In that case, the external IP can't be seen by the local machine.

I.O.W., if his box has a local network address (10.0.0.x, for example)
there's no way his box can see the external IP assigned via NAT.

That's why I suggested using either localhost,
or mapping 127.0.0.1 to the domain name in the hosts file.

The machine's name would work, too, for development purposes.

 

[Guest]

Hi Juan,

I think you're right...the external IP cannot be seen by the local machine
or anyone within that network, but using the internal IP, its
fine...phew!...I think this explains it, although I don't completely
understand.

So, I just have one last question: do you think (given the information) it
should be okay...I don't know of anyone else who is having trouble accessing
the app...just the users within the network.

Thanks Juan!

 

[Juan T. Llibre]

Hi, Justin.

re:
!> the external IP cannot be seen by the local machine or anyone
!> within that network, but using the internal IP, its fine

You could double-check with your network's administrators,
but it's quite likely that they're using NAT to assign local addresses.

re:
!> do you think (given the information) it should be okay...
!> I don't know of anyone else who is having trouble
!> accessing the app...just the users within the network.

You're fine as you are.

What you need to do is treat your internal network as an intranet.

i.e., have the users inside your network access your application
using either your machine's name or your local IP address.

http://yourmachinename/ or any of the private address ranges, i.e. :
http://172.xxx.xxx.xxx/ , http://10.x.x.xxx/ , http://192.xxx.xxx.xxx/ , http://169.xxx.xxx.xxx/
depending on your network's choice of IP address range.

Check with your network's admins...or simply test the addressing from a box inside the network.
If you can use your machine name, that should be your first option (it's easier to remember).

Your external clients can access the application normally,
using the domain name assigned to the external IP.

When IPv6 is in general use, this problem will disappear completely,
since there will be no more need for private IP addresses.

IPv6 provides enough IP addresses for every single computer in the world to have a unique IP address.

IPv6 supports 2128 addresses (340,282,366,920,938,463,463,374,607,431,768,211,456 exactly);
which is approximately 5×1028 addresses for each of the roughly 6.5 billion people alive today.

Those should be enough...

 

[Guest]

Hi Juan,

Sorry it took so long to get back to you...wow! you really know what's up.

Thank you for all of your help...the information you gave me has been
extremely helpful!