Listen ::
#This# This will accept connections on IPv6, but also on IPv4: (IPv4-mapped IPv6 addresses are used:
#CONNECT Jan 04 15:29:13 [23566]: Connect (file descriptor 6): host.terena.org [::ffff:192.87.30.2]
Listen 0.0.0.0)
Listen ::

# This will listen on IPv4 only
Listen 2001:610:148:dead::6660.0.0.0
# This will listen only on the specified IPv6 address. Not nice, but workable.
Listen 2001:610:148:dead::666

C:\Users\Administrator>netsh winhttp set proxy proxy6.terena.org:8888 "<local>"
Current WinHTTP proxy settings:
    Proxy Server(s) :  proxy6.terena.org:8888
    Bypass List     :  (none)