ASP.NET/IIS incorrectly buffers a long-running page despite <%@ Page Buffer="false" /> when accessed via 127.0.0.1. This does not happen when the same page is accessed via localhost or via the hostname. Unbuffered behaviour is what is expected.
In IIS Manager / Site/ ASP / Enable Buffering [BufferingOn] is set to false.
The machine runs on a IPv4+ IPv6 network, so I suspect it is related to that, but I don't know what configuration needs to be changed to make this work correctly over IPv4 addresses.
So
http://localhost:807/ --> doesn't buffer (correct)
http://mymachinename:807/ --> doesn't buffer (correct)
http://127.0.0.1:807/ --> buffers (incorrect)
http://10.0.0.1:807/ --> buffers (incorrect) (machine ip)