UPnP is based on HTTP and extensions of HTTP onto UDP. As mentioned earlier, UPnP is originally thought of to work in protected networks where devices communicate with each other, unhindered by firewalls. Since we also aim for our device to be connected to the Internet, we need to create two different HTTP interfaces: one for the Internet that is protected and one for the local area network that is unprotected. The protected interface will work on the standard HTTP port 80, and the UPnP server will, in our case, work on port 8080. This port number is not fixed by any standard; it can be any free port. Port numbers below 1024 will require superuser privileges when you run the application. Since notification of presence is done using multicast UDP, everybody will be aware of the IP and port number to use when communicating with the device. We begin by defining our HTTP server to use for UPnP:

private static HttpServer upnpServer;

We then create our second HTTP server...