This problem occurs if you set a breakpoint in a Visual Studio SharePoint solution, press F5 to run it, and then remain at a breakpoint longer than 90 seconds.
The Web server process that was being debugged has been terminated by Internet Information Services (IIS). This can be avoided by configuring Application Pool ping settings in IIS. See help for further details.
By default, the IIS application pool waits 90 seconds for an application to respond before it closes the application. This process is known as “pinging” the application. To resolve this issue, you can either increase the wait time or disable application pinging entirely.
To access the IIS app pool settings
Open IIS Manager.
In the Connections pane, expand the SharePoint server node and click Application Pools.
On the Application Pools page, select the SharePoint application pool (typically “SharePoint – 80”) and then, in the Actions pane, click Advanced Settings.
To increase the wait time before IIS timeout, change the value of Ping Maximum Response Time (seconds) to a value larger than 90 seconds.
To disable IIS pinging, set Ping Enabled to False.