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KNOCK! KNOCK! "WHOýS THERE?"

Using UPnP to Respond to Inquiries
by Edward F. Steinfeld

Start ý UPnP Overview ý Functions ý Device Addressing, Discovery, and Description ý Control, Event Messaging, and Presentation ý UPnP Forum ý Software Tools ý Hardware ý Easier Deployment ý Sources and PDF

FUNCTIONS

UPnP devices have embedded functionality called services. These services can include turning off the device, scanning inputs for data, or similar functions. These services can be initiated either by the device itself or by a control point. Some objects on the network can be both a control point and a device. This is especially true in factory systems.

There are six layers of functions of a UPnP-enabled device or control point (see Figure 2). Layers 0, 1, and 2 are fundamental; these layers exist in all devices and control points. Layers 3, 4, and 5 are optional. Control points can initiate an action on a device (layer 3). Many devices will have event messaging only (layer 4). They will create an event, and a control point will listen for these events. Devices can send data or results of an action they have taken without the initiation of a control point. Some devices may provide only a presentation user interface to the control point (layer 5). The control pointýs browser will display the web user interface of the device. This user interface may be to display events, status, or control the device.

Figure 2ýUPnPýs six layers consist of IP addressing, discovery, description of URLs and services, and optional control of other UPnP devices, event messaging, and presentation of the web page for the device. Layers 0 through 2 exist in all UPnP-enabled devices and control points.

The presentation layer is required because a pointer to the presentation URL is part of the device description. If the control point is handling the device programmatically and not through a web browser, the presentation layer is not required. Because every UPnP device uses a web server, it is simple to use the control pointýs browser as the front panel of the device. Allegro Software Development bundles layers 0, 1, 2, and 5 together and calls it UPnP Basic.

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