the type or namespace webget could not be found

In "project properties" make sure your "target framework" is set to : .NET Framework 4

and not: .NET Framework 4 Client Profile, or any lower .NET version.

You need to reference the System.ServiceModel.Web DLL.

Right-click the 'References' folder in your project and choose 'Add Reference...'. Scroll down 

to System.ServiceModel.Web and click 'OK'.

how can i check which app using port 443

Open command prompt(start -> run -> cmd) and type the following command :

C:\> netstat -aon | findstr 0.0:443
Last column of the output is the PID of the application using port 443.

You can find the application name in Task Manager. Go to Process Tab then in Menu Bar of Task Manager go to View -> Select Column -> Check "PID" and press Ok. Search for the PID in the list(Click Below "Show processes from all users" in case if you don't find the PID)