Comment 3 for bug 1604608

investigating this more, twisted's handling of ipv6 is fundamentally broken in some bad ways:
1) it allows "2001:db8::1:80" as an IP/Port combination, deciding that what you meant is [2001:db8::1]:80, rather than the default port on 2001:db8::1:80. 2001:db8::1:7f, on the other hand, means "default port on 2001:db8::1:7f.
2) if I have a hostname, it requires me to guess whether that will resolve to A or AAAA records, since I have to tell it which socket to create before I even know the answer (unless I look it up myself.)
2.1) Having said that, TCPClient doesn't even believe in ipv6 at all, as noted above.