How to Create an application to transfer files using Infrared Communication in .NET Compact Framework

Connectivity between smart devices and the personal computers are the necessity in this fast moving world. This feature is possible using the classes that are provided in the .Net Compact Framework. These classes that are used for the infrared communication is added to the namespace System.Net.Sockets. The Infrared Data Association (IrDA) has set some standards for socket programming and the Infrared communication programming has to implement these set standards in the IrDA specifications.

The Windows socket has to be invoked using the platform invoke in your personal computer since the full .Net Framework does not have the IrDA classes. This platform invoke on your personal computer is essential for communication between the smart devices and the personal computer. The protocol defined by IrDA is for point to point communication between devices.

This communication can be done over a short range only. Connecting multiple devices to the same host is also possible. In that case peer connectivity is established. Functionalities such as client server are implemented over the infrared connectivity. The server is usually the personal computer. The client would be the smart device that initiates the connectivity.

The IrDA protocol stack has a layer called the Information Access Service (IAS). This IAS layer has the Server and the Client component. The server has the services and the applications that are available for the IR connections that come to it. The client discovers the connections that are available in the server.

Some of the classes that are available are IrDACharacterSet, IrDAClient, IrDADeviceInfo, IrDAEndPoint, IrDAHints, and IrDAListener. Each of these classes has its own purpose. The IrDA devices have a character set that is supported by it. These character set supported is found by using the IrDACharacterSet class. Access to the client is provided by the IrDAClient class to send and receive data. The class IrDADeviceInfo is used to find the connections available with the server for that particular device.

The infrared port information is obtained using the IrDAEndPoint class. The type of device and the connection type are found as an enumeration list using the IrDAHints class. Monitoring the available connections for a particular device is possible when a socket is placed in the listening state. A socket is placed in such a state using the IrDAListener class. The start method of the class is called in order to place the socket in a listening state. Otherwise it is not available in the listening state.

To create an application to transfer files using InfraRed communication you need two devices which could be pocket PCs. One of the devices will be sending the data while the other one will receive the data. You will be using the IrDAClient class and its DiscoverDevices method to find the device that is available within the range in which it can access. Information about the devices that are within the range is got using the IrDADeviceInfo objects.

To make the device communicate with each other you have to create a send application that is used to send data and a receive application that would receive the data that is sent by the device. The Send application would be in one device and the Receive application would be in the other device. These are the minimum application that is to be created for communication between the two devices. For this purpose you could create a Send and Receive button which could be used to invoke the necessary action.

When you use the Send button to send a file to a device, the device to which it is sent should be listening to the devices. To make this possible you have to click the Receive button first so that the device is in the listening mode. Then click the send button to send the file to the other device which has the Receive application and is in the receive mode.

The tasks that are performed when you click the Send button are:

· Gets the file stream that is to be sent.
· An instance of IrDAClient is created with a service name for the application.
· The file stream is read into the IrDAClient for sending.

The tasks that are performed when you click the Receive button are:

· A stream is created to write the received file in a folder
· An IrDAEndPoint is created for the device that sends the file with the service name
· The listening service is started with the IrDAListener
· An IrDAClient object is create using the method AcceptIrDAClient
· Read the stream that has the data
· Write the received stream in to a text file

The steps that are followed to create applications to send and receive are as follows. First you can create an application for the sending device. The steps involved in creating the Send application would be,

1. Creating a Pocket PC application
2. Adding a Send button to the form in the application
3. Creating a text file that has to be sent in a folder
4. Add code to the click event of the Send button.

The steps for the Receive application in the receiving device would be,

1. Creating a Pocket PC application
2. Adding a Recieve button to the form in the application
3. Add code to the click event of the Receive button.

The algorithm behind the Send button’s click event should be as follows:

1. A collection is created to discover the devices available for communication.
2. The name of the first device that is detected is shown. If it couldn’t find it a message is displayed.
3. The file that is to be sent is opened and its stream is got.
4. The file size is got and it is written to the stream.
5. A buffer to read that file is created.
6. The file is read to the base stream.

The algorithm behind the Receive button’s click event should be as follows:

1. A collection is created to discover the devices available for communication.
2. The first IrDA device is found and is connected to it. If no devices are found a message is displayed.
3. A stream for writing is created.
4. The file is read to the buffer created for writing the file.
5. The file is written until there are no bytes to write.

To run the applications thus created you have to align the InfraRed ports of the devices. Before this you have to install the applications you have created in the respective devices. Click the Receive button in the receiving device. Then click the Send button in the device that will send the data or file. The text file that is sent to the receiving device should be available in the respective folder that is assigned for that purpose. Check whether you have received that file.

A walkthrough code is available for this kind of application in the MSDN website. You can download that code and test it. Here we have given the algorithm that is involved in developing that application to give you a clear idea on how to create an application for transferring files through the Infrared Communication port in the smart devices such as Pocket PCs and PDAs.

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