We have a networking application that can run from a service account as well as a regular user's account. The app tries to open up a loopback connection to another service running on the local machine. So for example it tries to connect to: 127.0.0.1 port 2000.
On a very small number of Windows machines we're seeing an issue where trying to connect to the loopback service from the Local System account causes a 'connection refused' error. If we run the app in the local user's context the connection to the same loopback service succeeds.
Why does the connection to 127.0.0.1:2000 fail when running as Local System and not fail when running on the user's desktop with the user's creds?
Does anyone know of weird anti-virus or firewall software that may cause this weird behavior?