Unable to connect to ASP.Net Development Server issue

I am debugging codeplex simple project. I am using

  • VSTS 2008
  • C#
  • Windows Vista x86 Enterprise.

I have not modified any code of this codeplex project, and just press F5 to run VideoPlayerWeb project.

The current issue I met with is error message —

Unable to connect to ASP.Net Development Server.

Here is my screen snapshots when clicking F5. Any ideas what is wrong?

screenshot 1

screenshot 2


Thank you for visiting the Q&A section on Magenaut. Please note that all the answers may not help you solve the issue immediately. So please treat them as advisements. If you found the post helpful (or not), leave a comment & I’ll get back to you as soon as possible.

Method 1

I had this problem with VS 2010, and it was as simple as terminating the “WebDev.WebServer40.EXE” process. Although the icon was no longer showing in the system tray, the process was still running.

Method 2

Could be a number of things…try these (check the last one first)…

  • Disable IPv6
  • Make sure there isnt an edit in the
    hosts file for localhost
  • Check firewall/virus settings to allow connections to/from
  • If you can preview in the browser
    make sure the URL in the browser uses
    the same port number as the port
    number shown in the ASP.NET dev
    server taskbar icon.
  • Try setting a fixed, predefined port
    in project properties

I got these from a couple of forums elsewhere, hopefully they can help. Good luck. Let us know what works and some more about your environment (firewall, anti virus etc) can help as well.

Method 3

Under project settings, try specifying a different port like 64773 for example. I have encountered this issue many times and it has always worked for me.

Method 4

It cause the already that project port server is running in the current thread. You need to end process using task manager.

Follow below step:

  1. Pres Ctrl+Alt+Delete (Task Manager)
  2. find the asp.net server like
    WebDev.WebServer40.exe for VS2010
    and press end process.
  3. Now u continue with vs2010 run

Method 5

I went to the project file and changed the development server port to 1504. Well 1504 worked on another project for me, so I went with that. Hope this helps.

Method 6

I have tried all of the above solutions and others from other websites too but with no luck.

What worked for me, was to rename or delete the applicationhost file:

C:UsersUserDocumentsIISExpressconfigapplicationhost < rename or delete.

Method 7

That is very odd! I hate to suggest something as simple as restarting Visual Studio…but that is what sounds like the best first place to start. Also, check your project settings. As you said that you just downloaded this and tried to run it…perhaps the solution/project is not set up to use the Casini server that is shipped with Visual Studio?

Method 8

Here are the steps

  1. ‘Website’ Menu in your visual studio ide.
  2. select ‘Start Options’
  3. enable ‘Use Custom Server’ radio button.
  4. Enter any URL you desire similar to ‘http://localhost:8010/MyApp

Note1: you can use any port number not only ‘8010’ but not designated port numbers like 8080(tcpip),25(smtp),21(ftp) etc.,

Note2: you can use any name not only ‘MyApp’

This solution works for sure unless your WebDev.Webserver.exe is physically corrupted.

Method 9

1) Unable to connect Asp.net development server ?
Answer: No way find for that error

Try 1)
Step 1: Select the “Tools->External Tools” menu option in VS or Visual Web Developer. This will allow you to configure and add new menu items to your Tools menu.

Step 2: Click the “Add” button to add a new external tool menu item. Name it “WebServer on Port 8010” (or anything else you     want).

Step 3: For the “Command” textbox setting enter this value: C:WINDOWSMicrosoft.NETFrameworkv2.0.50727WebD ev.WebServer.EXE     (note: this points to the

web-server that VS usually automatically runs).
Step 4: For the “Arguments” textbox setting enter this value: /port:8010 /path:$(ProjectDir) (or any port you like)

Step 5: Select the “Use Output Window” checkbox (this will prevent the command-shell window from popping up.

Once you hit apply and ok you will now have a new menu item in your “Tools” menu called “WebServer on Port 8010”. You can now   select any web project in your solution

and then choose this menu option to launch a web-server that has a root site on port 8010 (or whatever other port you want) for the project.
You can then connect to this site in a browser by simply saying http://localhost:8010/. All root based references will work     fine.

Step 6: The last step is to configure your web project to automatically reference this web-server when you run or debug a site  instead of launching the built-in

web-server itself. To-do this, select your web-project in the solution explorer, right click and select “property pages”. Select the “start options” setting on the left, and

under server change the radio button value from the default (which is use built-in webserver) to instead be “Use custom server”. Then set the Base URL value to be:


Obviously I don't know if this is the problem you had but definitely it is something similar, essentially the problem should be     that the same port used by your

Development Server is not available because it is already used by another web server.

Try 2)

Here are the steps

   1. 'Website' Menu in your visual studio ide.
   2. select 'Start Options'
   3. enable 'Use Custom Server' radio button.
   4. Enter any URL you desire similar to 'http://localhost:8010/MyApp'

Note1: you can use any port number not only '8010' but not designated port numbers like 8080(tcpip),25(smtp),21(ftp) etc.,

Note2: you can use any name not only 'MyApp'

This solution works for sure unless your WebDev.Webserver.exe is physically corrupted.

Both of not worked after that Windows repair option remain

Method 10

My solution was to turn off Internet Connection Sharing on my wireless adapter, after which it immediately worked. I made no other change. I suspect ICS’s DHCP server was interfering.

Method 11

Try commenting out the following line, if it exists, in your hosts file (%windir%System32driversetchosts):

::1     localhost

This worked for me using Visual Studio 2008 SP1 on Vista Ultimate x64 SP2.

Method 12

I got this problem a couple of times and done different things to fix it. When I got it this time all I did to stop getting “unable to connect to asp…” error, was rename the web app folder directory from xpCal to xpCal2. I also tried moving the web app directory to a different directory from C:users<me>desktop to C:users<me>desktopnew folder and it also worked.

I don’t know why it worked, does VS 2010 keep information about web apps seperate from web apps folder.

Method 13

In my case, when I had the ASP.NET Development Server crash, one thing that worked was to change the port for the project.

I suspect what happened was when the web server crashed it did not release a lock on the port. Even though it was not running in Task Manager, something was blocking a new instance of the web server from starting again on the original port. Changing the port was a decent enough work around. I could have rebooted, but who has time for that, right?

Details: Windows 7 x64, VS2010, .NET Framework 4.0, ASP.NET web site using the built in web server to VS2010.

BTW, I would be a little cautious with replacing the WebDev.WebServerServer.EXE as suggested in other posts. If that file has been corrupted then you have bigger problems with your OS.

Method 14

Just change the asp.netweb development server port from automatic to a specific port
e.g 8010
That’s what worked for me

Method 15

1) not reflecting HttpContext in class file ?

Answer:-Most of the time when using this syntax in class file is not working
we have to add reference then it work in class file

example using system.web write this syntax in class file

System.Web.HttpContext(HttpContext is not reflecting )

after that i add refrence system web than it reflect

Method 16

None of the above solutions worked for me, but I did find one that worked: opening up the Administrative Tools/Services window and stopping the “WebClient” service. It’s something of a pain to have to disable it when trying to work with my code, but it’s easier than the logging off and back on I used to have to do.

Method 17

–Problem Definition

—— whenever we debug our project (either by pressing ctrl+f5 or only f5) the first .exe which is called by VS is called WebDev.WebServer.EXE which got corrupted may be n number of reasons


—— We need to replace this file

——Step 1 —

    go location C:Program FilesCommon FilesMicrosoft SharedDevServer9.0

    You will find this file

——-Step 2 —
    download WebDev.WebServer.rar file from


——-Step 3 —
    NOTE :  You will need password for extraction this downloaded .rar file

    Password : optimusprime

—— Step 4 —
    Copy the downloaded WebDev.WebServer.EXE  file and replace in this below path

“C:Program FilesCommon FilesMicrosoft SharedDevServer9.0

——–step 5——

run the program

Method 18

Go to Run >> type >> cmd >> type
taskkill /IM webdev.webserver20.exe
and then try to re run the program

Method 19

In my case I was using Windows 8 and Windows Firewall was blocking WebDev.WebServer.EXE

So I went to the settings of Windows Firewall > Allow an app through Windows Firewall > Add new
and browse to C:Program Files (x86)Common FilesMicrosoft SharedDevServer11.0
Then select WebDev.WebServer to allow.

Method 20

For some poor souls out there starting using TypeMock on ASP.NET unit tests like me, you need to disable it in Visual Studio to avoid this error: In Tools->Add-in Manager, untick the boxes for TypeMock Isolator. I guess you need to switch this back on for your unit tests.

All methods was sourced from stackoverflow.com or stackexchange.com, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0

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