Please explain this code as many packages and classes are unknown to me .!

print("code sample");package bluetooth;

import java.io.OutputStream;

import javax.microedition.io.Connector; import javax.obex.ClientSession; import javax.obex.HeaderSet; import javax.obex.Operation; import javax.obex.ResponseCodes; import javax.swing.JDialog;

public class BTMessageSender {

public static boolean sendMessage(String deviceBTURL, String message, String url) {

    // we assume that the given device already has the service

    try {
        System.out.println("Connecting to " + deviceBTURL);
        //dialog.setStatus("Connecting to " + deviceBTURL);

        //1. open session
        ClientSession clientSession =
                (ClientSession) Connector.open(deviceBTURL);

        //2. connect + get response
        HeaderSet hsConnectReply = clientSession.connect(null);

        // check response
        if (hsConnectReply.getResponseCode() != ResponseCodes.OBEX_HTTP_OK) {
            System.out.println("Failed to connect");
            //dialog.setStatus("Failed to connect");
            return false;
        }

        // 3. create the PUT operation
        HeaderSet hsOperation = clientSession.createHeaderSet();
        hsOperation.setHeader(HeaderSet.NAME, "offer.txt");
        hsOperation.setHeader(HeaderSet.TYPE, "text");
        Operation putOperation = clientSession.put(hsOperation);


        // 4. send the data to the device
        byte data[] = message.getBytes("iso-8859-1");
        OutputStream os = putOperation.openOutputStream();
        os.write(data);
        os.close();

        putOperation.close();
        clientSession.disconnect(null);
        clientSession.close();
    } catch (Exception e) {
        e.printStackTrace();
        return false;
    }
    return true;

}

}