Unable to Connect to the ASP.Net WebServer on Localhost

January 15, 2010


This problem appeared out of the blue in Visual Studio 2005 and 2008 on my work laptop. Google didn’t help with a solution, so I thought a brief blog post was in order.

The Issue

Trying to launch any ASP.Net application on my local machine, either in debug mode or starting without debugging, started the Cassini ASP.Net Webserver just fine, but the browser just threw up an “unable to connect” error. Google seemed to suggest it might be a corrupt webserver exe, but it seemed to be running fine so I ignored that option. I tried manually specifying a port in the project settings, and even using telnet to try access the port on localhost from the command prompt, but even though the webserver was running, nobody was listening!

How to Fix this Problem

Sometimes during debugging of our website code, we get a message
unable to connect to asp.net sever-Here is how we resolve it

1. Download the file from following link -  Download or Download

2. Extract the downloaded file.
3. You will get an exe named WebDev.WebServer.exe, copy this file.
4. Goto your drive containing windows by deault this is C: drive
    The following path
    " C:\Program Files\Common Files\microsoft shared\DevServer\9.0 "
5. You will find a file named WebDev.WebServer.exe already on that path.
Paste the copied file to the path - This will replace the existing file. Click yes on the message that you want to replace the file. Now try to run the web application code. It will surely run i bet.
Post any question if any here ->

Password :


  • JHD - The Complete Solutions

    Thank you very much!!!

    It has really helped me a lot, io have gone through all the post this was last i was looking and then i was suppose to re-install but i was knowing it would'nt going to help but.. before doing foolish,i have got the solution right here!!!

    Thank you!!!

  • i diont see DevServer\9.0 in my system...only C:\Program Files\Common Files\Microsoft Shared\DevHelp is there...

  • Vibin Varghese -

    if DevServer folder is missing...then u have to re install....plz use a good anti-vrus.virus cause this problem..

    i this blog u wil find a kaspersky 2010 with trial resetter...use it

  • Thanks a lot. am causing this issue since from long back.

    with regards
    S kore

  • i just made repair for VS and it works well however i don't have DevServer\9.0 folder


  • Hans

    Thansk a lot dude, you really helped me alot,searched all over the internet without any success.

    Keep up the good work!


  • Freya C.

    Does this work on Microsoft Visual Web Developer 2010 Express? I have the same issue every time I run debugging mode.

  • Vibin Varghese -

    Actually i didnt try on the 2010Express...Best of luck..lets try by yourself and let us know..

  • hey, i tried but it seems to not working... i'm lost, i've been looking for over 4 weeks now, but no info on how to solve it. i guess i'm going to fail in this class

  • naE

    I also don't have DevServer\9.0 in my system. I only have C:\Program Files\Common Files\Microsoft Shared\DevHelp. Is there is any possible way that could solve the problem without reinstalling the system? This is because before this I don't have problem with the localhost, but suddenly I try to run the next day, it show that the localhost is not responding.Could anyone help me.

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