Network-related utilities and helper functions.
Interpret a string as a host:port pair. An IPv6 address MUST be escaped if accompanied by a port, because otherwise ambiguity ensues: 2001:db8:85a3::8a2e:370:7334 means both [2001:db8:85a3::8a2e:370:7334] and [2001:db8:85a3::8a2e:370]:7334.
>>> parse_host_port('server01:80')
('server01', 80)
>>> parse_host_port('server01')
('server01', None)
>>> parse_host_port('server01', default_port=1234)
('server01', 1234)
>>> parse_host_port('[::1]:80')
('::1', 80)
>>> parse_host_port('[::1]')
('::1', None)
>>> parse_host_port('[::1]', default_port=1234)
('::1', 1234)
>>> parse_host_port('2001:db8:85a3::8a2e:370:7334', default_port=1234)
('2001:db8:85a3::8a2e:370:7334', 1234)