Serve static files from an HTTP server

The SWI-Prolog HTTP server doesn't not server static files by default. You explicitly have to add a handler telling it to do so. The declarations below tell the server to serve files from the current directory under / on the server.

:- use_module(library(http/http_server)).
:- use_module(library(http/http_files)).

:- http_handler(root(.), http_reply_from_files('.', []), [prefix]).

Now, start the server and visit http://localhost:8080/.

?- http_server([port(localhost:8080)]).
% Started server at http://localhost:8080/
true.

Remarks

• Note that the localhost: only binds the loopback network, avoiding to expose your website to the outside world.
• The first argument of http_reply_from_files/3 is subject to search using absolute_file_name/3. This allows to abstract the physical location of the directory as well as virtually merge the contents of multiple physical directories.