I can normally debug my web service with no problem, but now I persistently get error "Unable to launch the IIS Express Web Server. Port 3268 is in use". I have looked at previous questions about this, but I am stuck:
it doesn't matter what port I use
rebooting, closing web browser, deleting web history etc all fail
tools like TCPView show that the port is NOT in use
I can start/stop IISExpress from a command prompt OK
normally, address localhost:3268 shows an error message in a browser - but after loading the project in Visual Studio (and BEFORE starting to debug the project, or doing anything at all to it), localhost:3268 shows a web page in the browser
The link that Krishna provided inspired me to open IIS and discover that there was a local web site in IIS with the same port (it was the same web service). I deleted that, and now I can debug my application again.
I cannot explain why I couldn't see the port in use, why it started offering the web page when the project was loaded in Visual Studio, and why I couldn't see that IIS was running in the task manager. I am guessing that Visual Studio was actually running it somehow.
Thanks to all respondents for their help!