When Showcase is started it initializes a web server to allow Showcase to be controlled by a remote or local web browser (or similar interface). This interface can be controlled on a network using IPv6, but requires some changes to the way that the hostname is specified, for example:
IPv4 local: http://localhost:5555/Showcase_control.html or http://127.1.1.1:5555/Showcase_control.html
IPv4 remote: http://20.21.34.101:5555/Showcase_control.html
IPv6 local: http://[::1]:5555/Showcase_control.html
IPv6 remote: http://[fe80::211:25ff:fe74:0a0f:c955]:5555/Showcase_control.html