In looking at RFC 3986, Port is separate from Host so I think we need to say that the SWD "host" value is defined as the RFC 3986 host and port sections of the authority portion. I'm assuming we don't want to include the "user" part of the authority portion.
Possible text change:
The SWD host value is extracted from the "authority" portion (as defined by RFC 3986) of the URL by concatenating the RFC 3986 host and port values of the URL. See section 2.2.3 for a non-normative example.