Accessing an https:// server can be achieved using the 
code skeleton below. The line :- use_module(library(http/http_ssl_plugin)). 
can actually be omitted because the plugin is dynamically loaded by
http_open/3 
if the https scheme is detected. See section 
5 for more information about security aspects.
:- use_module(library(http/http_open)).
:- use_module(library(http/http_ssl_plugin)).
    ...,
    http_open(HTTPS_url, In, []),
    ...