My previous posting “Using Bluetooth stack in desktop application” was quite a success if measured by the number of comments. It seems that there aren’t many tutorials or articles about the Desktop usage of Bluetooth.
Here is a next chapter in the same category: using Bluetooth to send files from a computer to a mobile phone.
Read on if you are interested…
I wrote this small application so that I could send files (images) to my phone using the Bluetooth.
Creating a new application
I used NetBeans IDE to create this application. First I created a new Java application project. I created a following files for the app:
- ApplicationContext.java - Contains list of devices near-by
- ApplicationFrame.java – Actual UI, extends JFrame
- BluetoothBrowser.java - Helper class to browse near-by devices
- ListItem.java - DAO class used by ApplicationFrame
- Main.java - Application entry point
- SendFileTask.java – The OBEX magic for sending a file
I designed the UI with NetBeans IDE’s Matisse editor, which allows developer to design desktop user interfaces very easily.
Next I added code for searching devices when user presses the Refresh button. This was already discussed in the previous article. Also simple coding was done for browsing the file when Browse button gets clicked.
Next step was to add the actual business logic for sending the file to a selected Bluetooth device when Upload file to device button is clicked.
Code for upload button action performed
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// Get selected item from list
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ListItem selectedItem =
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(ListItem) deviceList.getSelectedValue();
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RemoteDevice device = selectedItem.getDevice();
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// Build URL for the bluetooth device, note the port 9
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String url =
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"btgoep://" + device.getBluetoothAddress() + ":9";
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// Get file as bytes
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FileInputStream stream =
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int size = (int) f.length();
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byte[] file = new byte[size];
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stream.read(file);
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// Filename
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// Trigger the task in a different thread
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// so it won’t block the UI
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SendFileTask task =
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new SendFileTask(url, file, filename);
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task.run();
Next step was to write the code for sending a file using the OBEX protocol.
Code for send file task
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/*
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* To change this template, choose Tools | Templates
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* and open the template in the editor.
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*/
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package bluetoothfileexchange;
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import java.io.OutputStream;
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import javax.microedition.io.Connection;
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import javax.microedition.io.Connector;
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import javax.obex.ClientSession;
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import javax.obex.HeaderSet;
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import javax.obex.Operation;
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/**
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*
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* @author Tommi Laukkanen (tlaukkanen at gmail dot com)
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*/
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private String btConnectionURL;
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private byte[] file;
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private String filename;
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public SendFileTask(
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this.btConnectionURL = url;
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this.file = file;
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this.filename = filename;
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}
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public void run() {
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try {
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Connection connection =
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Connector.open( btConnectionURL );
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// connection obtained
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// now, let’s create a session
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// and a headerset objects
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ClientSession cs =
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(ClientSession) connection;
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HeaderSet hs = cs.createHeaderSet();
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// now let’s send the connect header
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cs.connect(hs);
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hs.setHeader(HeaderSet.NAME, filename);
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// content-type could be
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// checked from a filename
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hs.setHeader(HeaderSet.TYPE, "image/jpeg");
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hs.setHeader(
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HeaderSet.LENGTH,
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OutputStream outputStream =
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putOperation.openOutputStream();
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outputStream.write(file);
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// file push complete
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outputStream.close();
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putOperation.close();
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cs.disconnect(null);
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connection.close();
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e.printStackTrace();
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}
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}
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}
That was it. Now when the application is run, user can send a selected file to a selected Bluetooth device. I get a normal “Message received” notification on my mobile phone, Nokia N80, when I send a new image file to the phone.
You can download the whole project along with source codes from here.