multicastsocket.java

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/*
 * @(#)MulticastSocket.java	1.47 06/10/10
 *
 * Copyright  1990-2008 Sun Microsystems, Inc. All Rights Reserved.  
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER  
 *   
 * This program is free software; you can redistribute it and/or  
 * modify it under the terms of the GNU General Public License version  
 * 2 only, as published by the Free Software Foundation.   
 *   
 * This program is distributed in the hope that it will be useful, but  
 * WITHOUT ANY WARRANTY; without even the implied warranty of  
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU  
 * General Public License version 2 for more details (a copy is  
 * included at /legal/license.txt).   
 *   
 * You should have received a copy of the GNU General Public License  
 * version 2 along with this work; if not, write to the Free Software  
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  
 * 02110-1301 USA   
 *   
 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa  
 * Clara, CA 95054 or visit www.sun.com if you need additional  
 * information or have any questions. 
 *
 */

package java.net;

import java.io.IOException;
import java.io.InterruptedIOException;
import java.util.Enumeration;

/**
 * The multicast datagram socket class is useful for sending
 * and receiving IP multicast packets.  A MulticastSocket is
 * a (UDP) DatagramSocket, with additional capabilities for
 * joining "groups" of other multicast hosts on the internet.
 * <P>
 * A multicast group is specified by a class D IP address
 * and by a standard UDP port number. Class D IP addresses
 * are in the range <CODE>224.0.0.0</CODE> to <CODE>239.255.255.255</CODE>,
 * inclusive. The address 224.0.0.0 is reserved and should not be used.
 * <P>
 * One would join a multicast group by first creating a MulticastSocket
 * with the desired port, then invoking the
 * <CODE>joinGroup(InetAddress groupAddr)</CODE>
 * method:
 * <PRE>
 * // join a Multicast group and send the group salutations
 * ...
 * String msg = "Hello";
 * InetAddress group = InetAddress.getByName("228.5.6.7");
 * MulticastSocket s = new MulticastSocket(6789);
 * s.joinGroup(group);
 * DatagramPacket hi = new DatagramPacket(msg.getBytes(), msg.length(),
 *                             group, 6789);
 * s.send(hi);
 * // get their responses!
 * byte[] buf = new byte[1000];
 * DatagramPacket recv = new DatagramPacket(buf, buf.length);
 * s.receive(recv);
 * ...
 * // OK, I'm done talking - leave the group...
 * s.leaveGroup(group);
 * </PRE>
 *
 * When one sends a message to a multicast group, <B>all</B> subscribing
 * recipients to that host and port receive the message (within the
 * time-to-live range of the packet, see below).  The socket needn't
 * be a member of the multicast group to send messages to it.
 * <P>
 * When a socket subscribes to a multicast group/port, it receives
 * datagrams sent by other hosts to the group/port, as do all other
 * members of the group and port.  A socket relinquishes membership
 * in a group by the leaveGroup(InetAddress addr) method.  <B>
 * Multiple MulticastSocket's</B> may subscribe to a multicast group
 * and port concurrently, and they will all receive group datagrams.
 * <P>
 * Currently applets are not allowed to use multicast sockets.
 *
 * @author Pavani Diwanji
 * @since  JDK1.1
 */
public
class MulticastSocket extends DatagramSocket {
    /**
     * Create a multicast socket.
     * 
     * <p>If there is a security manager, 
     * its <code>checkListen</code> method is first called
     * with 0 as its argument to ensure the operation is allowed. 
     * This could result in a SecurityException.
     * <p>
     * When the socket is created the 
     * {@link DatagramSocket#setReuseAddress(true)} method is 
     * called to enable the SO_REUSEADDR socket option. 
     *
     * @exception IOException if an I/O exception occurs
     * while creating the MulticastSocket
     * @exception  SecurityException  if a security manager exists and its  
     *             <code>checkListen</code> method doesn't allow the operation.
     * @see SecurityManager#checkListen
     * @see java.net.DatagramSocket#setReuseAddress(boolean) 
     */
    public MulticastSocket() throws IOException {
	this(new InetSocketAddress(0));
    }

    /**
     * Create a multicast socket and bind it to a specific port.
     * 
     * <p>If there is a security manager, 
     * its <code>checkListen</code> method is first called
     * with the <code>port</code> argument
     * as its argument to ensure the operation is allowed. 
     * This could result in a SecurityException.
     * <p>
     * When the socket is created the
     * {@link DatagramSocket#setReuseAddress(true)} method is
     * called to enable the SO_REUSEADDR socket option. 
     * 
     * @param port port to use
     * @exception IOException if an I/O exception occurs
     * while creating the MulticastSocket
     * @exception  SecurityException  if a security manager exists and its  
     *             <code>checkListen</code> method doesn't allow the operation.
     * @see SecurityManager#checkListen
     * @see java.net.DatagramSocket#setReuseAddress(boolean) 
     */
    public MulticastSocket(int port) throws IOException {
	this(new InetSocketAddress(port));
    }

    /**
     * Create a MulticastSocket bound to the specified socket address.
     * <p>
     * Or, if the address is <code>null</code>, create an unbound socket.
     * <p>
     * <p>If there is a security manager, 
     * its <code>checkListen</code> method is first called
     * with the SocketAddress port as its argument to ensure the operation is allowed. 
     * This could result in a SecurityException.
     * <p>
     * When the socket is created the
     * {@link DatagramSocket#setReuseAddress(true)} method is
     * called to enable the SO_REUSEADDR socket option. 
     *
     * @param bindaddr Socket address to bind to, or <code>null</code> for
     *                 an unbound socket.
     * @exception IOException if an I/O exception occurs
     * while creating the MulticastSocket
     * @exception  SecurityException  if a security manager exists and its  
     *             <code>checkListen</code> method doesn't allow the operation.
     * @see SecurityManager#checkListen
     * @see java.net.DatagramSocket#setReuseAddress(boolean) 
     *
     * @since 1.4
     */
    public MulticastSocket(SocketAddress bindaddr) throws IOException {
	super((SocketAddress) null);

	// Enable SO_REUSEADDR before binding
	setReuseAddress(true);

        getImpl().setIsMulticastSocket();
	if (bindaddr != null) {
	    bind(bindaddr);
	}
    }

    /**
     * The lock on the socket's TTL. This is for set/getTTL and
     * send(packet,ttl).
     */
    private Object ttlLock = new Object();

    /**
     * The lock on the socket's interface - used by setInterface
     * and getInterface
     */
    private Object infLock = new Object();

    /**
     * The "last" interface set by setInterface on this MulticastSocket
     */
    private InetAddress infAddress = null;


    /**
     * Set the default time-to-live for multicast packets sent out
     * on this <code>MulticastSocket</code> in order to control the 
     * scope of the multicasts.
     *
     * <p>The ttl is an <b>unsigned</b> 8-bit quantity, and so <B>must</B> be
     * in the range <code> 0 <= ttl <= 0xFF </code>.
     *
     * param ttl the time-to-live
     * exception IOException if an I/O exception occurs
     * while setting the default time-to-live value
     * deprecated use the setTimeToLive method instead, which uses
     * <b>int</b> instead of <b>byte</b> as the type for ttl.
     * see #getTTL()
     *
    public void setTTL(byte ttl) throws IOException {
	if (isClosed())
	    throw new SocketException("Socket is closed");
	getImpl().setTTL(ttl);
    }
     */

    /**
     * Set the default time-to-live for multicast packets sent out
     * on this <code>MulticastSocket</code> in order to control the 
     * scope of the multicasts.
     *
     * <P> The ttl <B>must</B> be in the range <code> 0 <= ttl <=
     * 255</code> or an IllegalArgumentException will be thrown.
     * @exception IOException if an I/O exception occurs
     * while setting the default time-to-live value
     * @param ttl the time-to-live
     * @see #getTimeToLive()
     */
    public void setTimeToLive(int ttl) throws IOException {
	if (ttl < 0 || ttl > 255) {
	    throw new IllegalArgumentException("ttl out of range");
	}
	if (isClosed())
	    throw new SocketException("Socket is closed");
	getImpl().setTimeToLive(ttl);
    }

    /**
     * Get the default time-to-live for multicast packets sent out on
     * the socket.
     *
     * exception IOException if an I/O exception occurs
     * while getting the default time-to-live value
     * return the default time-to-live value
     * deprecated use the getTimeToLive method instead, which returns
     * an <b>int</b> instead of a <b>byte</b>.
     * see #setTTL(byte)
     *
    public byte getTTL() throws IOException {
	if (isClosed())
	    throw new SocketException("Socket is closed");
	return getImpl().getTTL();
    }
     */

    /**
     * Get the default time-to-live for multicast packets sent out on
     * the socket.
     * @exception IOException if an I/O exception occurs while
     * getting the default time-to-live value
     * @return the default time-to-live value
     * @see #setTimeToLive(int)
     */
    public int getTimeToLive() throws IOException {
	if (isClosed())
	    throw new SocketException("Socket is closed");
	return getImpl().getTimeToLive();
    }

    /**
     * Joins a multicast group. Its behavior may be affected by
     * <code>setInterface</code> or <code>setNetworkInterface</code>.
     * 
     * <p>If there is a security manager, this method first
     * calls its <code>checkMulticast</code> method
     * with the <code>mcastaddr</code> argument
     * as its argument.
     * 
     * @param mcastaddr is the multicast address to join
     * 
     * @exception IOException if there is an error joining
     * or when the address is not a multicast address.
     * @exception  SecurityException  if a security manager exists and its  
     * <code>checkMulticast</code> method doesn't allow the join.
     * 
     * @see SecurityManager#checkMulticast(InetAddress)
     */
    public void joinGroup(InetAddress mcastaddr) throws IOException {
        if (isClosed()) {
            throw new SocketException("Socket is closed");
        }

        SecurityManager security = System.getSecurityManager();
        if (security != null) {
            security.checkMulticast(mcastaddr);
        }

	if (!mcastaddr.isMulticastAddress()) {
	    throw new SocketException("Not a multicast address");
	}

	getImpl().join(mcastaddr);
    }

    /**
     * Leave a multicast group. Its behavior may be affected by
     * <code>setInterface</code> or <code>setNetworkInterface</code>.
     * 
     * <p>If there is a security manager, this method first
     * calls its <code>checkMulticast</code> method
     * with the <code>mcastaddr</code> argument
     * as its argument.
     * 
     * @param mcastaddr is the multicast address to leave
     * @exception IOException if there is an error leaving
     * or when the address is not a multicast address.
     * @exception  SecurityException  if a security manager exists and its  
     * <code>checkMulticast</code> method doesn't allow the operation.
     * 
     * @see SecurityManager#checkMulticast(InetAddress)
     */
    public void leaveGroup(InetAddress mcastaddr) throws IOException {
        if (isClosed()) {
            throw new SocketException("Socket is closed");
        }

        SecurityManager security = System.getSecurityManager();
        if (security != null) {
            security.checkMulticast(mcastaddr);
        }

	if (!mcastaddr.isMulticastAddress()) {
            throw new SocketException("Not a multicast address");
        }

	getImpl().leave(mcastaddr);
    }

    /**
     * Joins the specified multicast group at the specified interface.
     *
     * <p>If there is a security manager, this method first
     * calls its <code>checkMulticast</code> method