Host request header specifies the host and port number of the server to which the request is being sent.
If no port is included, the default port for the service requested is implied (e.g.,
443 for an HTTPS URL, and
80 for an HTTP URL).
Host header field must be sent in all HTTP/1.1 request messages. A
400 (Bad Request) status code may be sent to any HTTP/1.1 request message that lacks or contains more than one
Host header field.