udphandler.java

来自「J2ME MIDP_Example_Applications」· Java 代码 · 共 223 行

// Copyright 2003 Nokia Corporation.
//
// THIS SOURCE CODE IS PROVIDED 'AS IS', WITH NO WARRANTIES WHATSOEVER,
// EXPRESS OR IMPLIED, INCLUDING ANY WARRANTY OF MERCHANTABILITY, FITNESS
// FOR ANY PARTICULAR PURPOSE, OR ARISING FROM A COURSE OF DEALING, USAGE
// OR TRADE PRACTICE, RELATING TO THE SOURCE CODE OR ANY WARRANTY OTHERWISE
// ARISING OUT OF ANY PROPOSAL, SPECIFICATION, OR SAMPLE AND WITH NO
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// RIGHTS GRANTED HEREUNDER DOES NOT INFRINGE OR MAY NOT CAUSE INFRINGEMENT
// OF ANY PATENT OR OTHER INTELLECTUAL PROPERTY RIGHTS OWNED OR CONTROLLED
// BY THIRD PARTIES
//
// Furthermore, information provided in this source code is preliminary,
// and may be changed substantially prior to final release. Nokia Corporation
// retains the right to make changes to this source code at
// any time, without notice. This source code is provided for informational
// purposes only.
//
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// Corporation.
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//
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// source code. The licensee has the right to market, sell, distribute and
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// unnamed package

import java.io.IOException;
import java.util.Vector;
import javax.microedition.io.Connector;
import javax.microedition.io.Datagram;
import javax.microedition.io.UDPDatagramConnection;


class UDPHandler
    implements Runnable
{
    // The following value was chose arbitrarily
    // for this simple example
    private static final int DEFAULT_DATAGRAM_SIZE = 1024;

    private final String url;
    private final Vector writeQueue = new Vector();

    private UDPDatagramConnection conn = null;
    private Datagram receiveDatagram = null;
    private UDPHandlerListener listener = null;
    private boolean aborting = false;


    UDPHandler(String url)
        throws IOException
    {
        if ((url == null) || !url.startsWith("datagram://"))
        {
            throw new IllegalArgumentException("Bad url");
        }
        else
        {
            this.url = url;
            new Thread(this).start();
        }
    }


    void setUDPHandlerListener(UDPHandlerListener listener)
    {
        this.listener = listener;
    }


    void close()
    {
        if (!aborting)
        {
            synchronized (this)
            {
                aborting = true;
            }

            synchronized (writeQueue)
            {
                writeQueue.notify();
            }

            if (conn != null)
            {
                try
                {
                    conn.close();
                }
                catch (IOException ioe)
                {
                    // nothing we can do
                }
            }
        }
    }


    public void run()
    {
        try
        {
            conn = (UDPDatagramConnection) Connector.open(url);
            receiveDatagram = conn.newDatagram(DEFAULT_DATAGRAM_SIZE);

            startWriteQueue(); // start writer
        }
        catch (IOException e)
        {
            listener.handleError("Error opening datagram connection to: '" +
                                 url + "'");
            return;
        }

        // start reader
        while (! aborting)
        {
            try
            {
                conn.receive(receiveDatagram);
                if (listener != null)
                {
                    byte[] data = receiveDatagram.getData();
                    int length = receiveDatagram.getLength();
                    byte[] temp = new byte[length];
                    System.arraycopy(data, 0, temp, 0, length);
                    listener.handleDatagram(temp);
                    receiveDatagram.reset();
                    receiveDatagram.setLength(DEFAULT_DATAGRAM_SIZE);
                }
            }
            catch (IOException ioe)
            {
                listener.handleError("I/O Exception: " + ioe.getMessage());
            }
        }
    }


    void queueMessageForSending(byte[] data)
    {
        if (data.length > DEFAULT_DATAGRAM_SIZE)
        {
            throw new IllegalArgumentException(
                           "Message too long: limit is " +
                           DEFAULT_DATAGRAM_SIZE + " bytes");
        }

        synchronized(writeQueue)
        {
            writeQueue.addElement(data);
            writeQueue.notify();
        }
    }


    private void startWriteQueue()
    {
        Runnable writer = new Runnable()
        {
            public void run()
            {
                while (!aborting)
                {
                    if (!writeQueue.isEmpty())
                    {
                        byte[] sendData = (byte[]) writeQueue.elementAt(0);
                        try
                        {
                            // send the datagram
                            Datagram datagram = conn.newDatagram(
                                                         sendData,
                                                         sendData.length);
                            conn.send(datagram);
                            writeQueue.removeElement(sendData);

                            // You could do a callback to the listener
                            // to say that the datagram was set (but
                            // (remembering that datagram delivery is
                            // unreliable anyways).
                        }
                        catch (IOException e)
                        {
                            close();
                        }
                    }

                    synchronized(writeQueue)
                    {
                        if (writeQueue.size() == 0)
                        {
                            try
                            {
                                writeQueue.wait();
                            }
                            catch (InterruptedException e)
                            {
                                // can't happen in MIDP
                            }
                        }
                    }
                }
            }
        };

        Thread writeThread = new Thread(writer);
        writeThread.start();
    }
}