The active property sets whether the web server on the Make Controller is running or not. The default web server does not really do anything too interesting, but provides a count of the number of requests it has served. You can access the web server by typing the board's IP address into your favorite browser. You can check the board's IP address in mchelper.
To turn the web server on, send the message
/webserver/active 1
/network/webserver 0
Listen Port
The listenport property sets which port the web server should listen on for incoming requests. By default this is set to 80, the standard port for HTTP.
To listen on port 8080, send the message
/webserver/listenport 8080
Note that the server will most likely already be listening on the previous port, and it won't update its port until it serves that last request it's waiting for.