When I try to start debugging my windows phone 8 app in Emulator WVGA 512MB
the following error message is showing
The Windows Phone Emulator wasn\'t
I had the same problem. After a long investigation and checking the event log, learned that windows firewall is blocking the emulator connecting to the virtual machine. With that information it is simple to fix the problem.
Yes! Just navigate to Control Panel -> System and Security -> Windows Firewall -> Allow app or feature through Windows Firewall. And click on Add another app button and browse the emulator's path (typically "C:\Program Files (x86)\Microsoft XDE\8.0\XDE.exe" but may vary based on your installation location). Choose the appropriate network type that you want and add the new item.
Now go back to VS and run your application (close any emulator instance that you have opened already), everything should work fine now!