Opens a HTTP connection.
The HTTP method is specified in method and the URL to use in url.
The Host
header for the request will be set to the value
host:port. This can be overridden through the
HttpClientRequest interface before the request is sent. NOTE
if host is an IP address this will still be set in the Host
header.
For additional information on the sequence of events during an HTTP transaction, and the objects returned by the futures, see the overall documentation for the class HttpClient.