We are differentiating two large groups of devices. The first group are devices which actively take part in UPnP communication.
This means they are discoverable by other UPnP devices. We call this group UPnP Servers and -Renderers.
The other group consists of devices who pull data from UPnP devices but are not visible by others.
One such example is the PS3. This group is just called Players.
UPnP Servers and -Renderers are automatically queried by the Magpie tool and you do not need to do anything yourself (except for submitting the data).
Players are queried only if they are sending UPnP queries. Some do this themselves, some do this only if browsing.
Therefore the Magpie tool contains a pseudo UPnP MediaServer. When you browse this server's folders, the tool detects the Player and captures all the information the device grabs from the server.
Confused? Just try it out.