Intercepting web requests from an application and modifying response

[Kerlingen]

You might want to edit your hosts file to redirect the traffic and then run the webserver part on your computer. If it's a simple webcheck with static requests there are many tiny webservers or networks tools available which can serve the requests.

If it's more complicated you might need to switch to some script language to process and serve the requests.

But if it's just a simple patch you already know the location to I would prefer patching over running a webserver. You might have redirected other addresses in your hosts file which would get served with unknown data and might behave differently.