Well? Is it?
How’s this for a definitive answer: “Yes and no.”
We find the answer in RFC 2616 section 14.23:
The Host request-header field specifies the Internet host and port number of the resource being requested, as obtained from the original URI: “Host” “:” host [ “:” port ]
A “host” without any trailing port information implies the default port for the service requested (e.g., “80” for an HTTP URL).
So if an HTTPS request is made to a non-standard port, say 29043, then you should send a port even though the RFC doesn’t compel you to. And if you make HTTP or HTTPS requests to standard ports, then it’s probably best to omit the port string.
The above is my interpretation. I’ve maintained an HTTP client for thirteen years and this has been a point of contention. In the course of all that time, I’ve added and dropped :port from the header. Like Jason in a hockey mask, it keeps coming back. In its latest iteration, siege implements the interpretation you see above. If the port is non-standard, it appends :port to the string. If it is standard, then it simply sends the host.
Look for this feature in siege-3.0.8