This essay has been submitted by a student. This is not an example of the work written by our professional essay writers.
Devices are components, usually are hardware, which are attached to the network. For examples printers, web cameras, and video systems. These devices include 1 or more services. For example, a web cam device included several services which is support power on and off, recording, capture, and etc, after that play control may support several actions such as play, pause, rewind, and fast forward. In order to communicate those devices, the web services are necessary to implement on devices. Web Services on Device's main objective is provides interoperability, since these devices do not rely on any specific programming language nor hardware architecture. So that web service on device can help each hardware component sharing the information without any compatibility issues. Besides that web service on devices included secure web service messaging, dynamically discover, describe a web service, eventing on resource-constrained devices, subscribe events. That is appropriate for network-connected devices, such as printer, scanner, web cam, mice and etc. We can control these devices from another place to do some of the task, such as printing, scanning, recorder, capture video and so on. How to connect these devices through the network environment? Web services will be solving this kind of problem. Its objectives are similar with the Universal Plug and Play (UPnP), which are users plug in new hardware(e.g.: pen drive, external hard disk, printer, web cam and etc) on the pc after that pc will automatically communicate with that new hardware for establish the connection between pc and hardware.
A typical usage scenario for Web service device is:
1. A device is connected to the network and receives a unique IP address.
2. The device then announces its presence.
3. A client uses the Function Discovery API to discover the device and enumerate its services. The Function Discovery runtime works through WSD to accomplish this for WSD devices, although it is possible for an application to call directly through to these WSD discovery functions.
4. The client invokes service functions on the device and can optionally subscribe to device events.
The first generation of web services on devices was defined for using the internet to allow remote printing to take place. Usually, the printers required a cable connect to a switches or hub in order to communicate it. But nowadays, it is possible for the people can be sent the documents through the internet to a printer from other places, such as at home, office and etc. The latest of product like PDA, I phone 4, GPS, Mobile phone are also examples of web services for devices. These devices are able to use a wireless technology to connect with an Internet service provider, browse the web, telephone calls, faxes documents, send email and video call, all from a handheld device. These services requires a web services to handle it in order the devices can be exchange the information between two different software platform. Increasingly, the demand of web services on devices was higher. Web services for devices also make good use of home security and control as well. Persons who are traveling may use the Internet to manage activities at home, such as turning lights off and on, adjusting the heating thermostat, viewing CCTV that are installed on the home. We can control the home's equipment and home alarm system anytime whatever where we are located (must have an internet). The web services for device are very useful for all people.
Below is a web service for devices diagram:
MESSAGEs include discovery,
description, control, and eventing
**Web services require the use of several related XML-based technology such as WSDL, SOAP, UDDI. I will not discuss it on this topic.
The diagram show that the client/user wants to access the device, it must be go through web services layered by sending the MESSAGEs, which is XML messages. Then the web services interface will receive the XML messages from the client, it will process it and send to the device. The device will know which services are going to use, that device will send XML messages, which is attached the services information to the interfaces. Web services interface will process the XML messages from the device after processing the client will received information from the interface. The connection between client and device will be established. The clients are able to control the device's services.
1. Client send the discovery messages to device through web service interface
2. Device received the discovery messages from client, after that device will sent a description (WSDL) to client through web service interface.
3. After client receives the description (WSDL) from device, client will sent a control messages to device in order to get device's service.
4. Device received the control messages from client, then it will sent back the events that client requested.