Jun 08, 2017 04:46 PM|PatriceSc|LINK
localhost and localhost:80 is the same site.
When processing a request, IIS must have a way to select which site should process this incoming request. It is done by seeing which site best matches the IP address, port address and host header name for the incoming request.
So you have to configure at least one of those information else the default web site is still used (the default web site is configured for port 80 which is the default http port).