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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

UPnP OVERVIEW

UPnP is an architecture for peer-to-peer networking of intelligent machines, appliances, wireless devices, and computers of varying form factors. UPnP defines a set of common services (protocols) that devices can use to join a network and describe themselves and their capabilities, enabling other devices and people to use them without complicated setup or configuration.

UPnP has six basic layers or functions, device addressing, device discovery, device description, action invocation, event messaging, and presentation or human interface.

UPnP is a protocol for data transmission. It doesnýt move byte codes or use ActiveX controls. It is an independent operating system built on various existing network standards. UPnP is designed to work in a peer-to-peer or ad hoc network. Devices can use a DHCP server or Auto IP to automatically choose an IP address from a range of addresses.

When a device is added to a network, it will advertise itself and all control points will then know the device is on-line. A control point, when added, can search the network for devices. After a device is discovered, a description of the device and the services it provides are obtained. This information is presented in an XML document.

Control points can initiate an action on the device by sending a message to the device. The message is sent to a URL obtained from the description sent by the device. After the action is complete, the device notifies the control point of the completion.

Often devices donýt need to be told to perform their function, however, they do need to report their status to one or more control points. In UPnP, this is called event messaging, a basic push model. Events are sent only to the control points that have subscribed to a deviceýs events.

Each device can have a unique presentation or web home page. Its URL is sent to control points as part of the description (see Figure 1).

Figure 1ýUPnP devices can be devices, control points, or both. Devices have services that can be monitored or controlled by a control point.

Today the only UPnP control points available are with Windows Me systems. All standard Windows Me systems come with UPnP software, but it has to be installed. Intel provides a free SDK to create a Linux-based control point. There can be any number of vendor-enabled or Windows Me control points on a network.

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