If you are using a Unix system, one of the options for deploying the SWI-Prolog based server is to use (x)inetd. This starts a server for every client. The server will try to use Keep-Alive connections, which can greatly enhance the performance if multiple requests need to be made. If Keep-Alive is not used, this is very similar to using SWI-Prolog as a GCI script. See library(cgi) for details.

If you have applications that take long to load, you want to do session management, etc., we advice to use the multi-threaded server.

To set it all up

1. Create a server directory: In this example, $PLBASE is the installation directory of SWI-Prolog. This variable is set using the first command.

   % eval `swipl --dump-runtime-variables`
   % sudo mkdir -p /srv/www/html/srv_demo
   % cd !$
   % sudo cp $PLBASE/doc/packages/examples/http/demo_body.pl .
   % sudo cp $PLBASE/doc/packages/examples/http/demo_inetd .

2. Create an (x)inetd entry
   • If you are using xinetd:

     % sudo tee /etc/xinetd.d/demo_swi_srv << EOF
     service demo_swi_srv
     {
     port                    = 8080
     socket_type             = stream
     protocol                = tcp
     wait                    = no
     user                    = nobody
     server                  = /srv/www/html/srv_demo/demo_inetd
     log_on_failure  += USERID
     log_on_success  += PID HOST EXIT
     }
     EOF

   • If you are using inetd:

     % sudo tee -a /etc/inetd.conf << EOF
     demo_swi_srv stream tcp nowait nobody /srv/www/html/srv_demo/demo_inetd
     EOF

3. Add association to the services file. This can be done by adding the following line to /etc/services

   demo_swi_srv   8080/tcp

4. Restart (x)inetd

   % sudo /etc/init.d/xinetd reload

   or

   % sudo /etc/init.d/inetd reload

5. Point your browser to http://localhost:8080 and try
   • http://localhost:8080/upload
   • http://localhost:8080/foreign
   • http://localhost:8080/error

author

- Nicos Angelopoulos