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 * This code 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.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code 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 in the LICENSE file that

 * accompanied this code).

 *

 * 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.

 *

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 */

package java.net;

import java.io.IOException;

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  1.1

 */

public

class MulticastSocket extends DatagramSocket {

    /**

     * Used on some platforms to record if an outgoing interface

     * has been set for this socket.

     */

    private boolean interfaceSet;

    /**

     * Create a multicast socket.

     *

     * <p>If there is a security manager,

     * its {@code checkListen} 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(boolean)} method is

     *

     * @exception IOException if an I/O exception occurs

     * while creating the MulticastSocket

     * @exception  SecurityException  if a security manager exists and its

     *             {@code checkListen} 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} method is first called

     * with the {@code port} 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(boolean)} 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} 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}, create an unbound socket.

     *

     * <p>If there is a security manager,

     * its {@code checkListen} 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(boolean)} method is

     * called to enable the SO_REUSEADDR socket option.

     *

     * @param bindaddr Socket address to bind to, or {@code null} 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} 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);

        if (bindaddr != null) {

            try {

                bind(bindaddr);

            } finally {

                if (!isBound())

                    close();

            }

        }

    }

    /**

     * 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} 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 }.

     *

     * @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()

     */

    @Deprecated

    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} in order to control the

     * scope of the multicasts.

     *

     * <P> The ttl <B>must</B> be in the range {@code  0 <= ttl <=

     * 255} or an {@code IllegalArgumentException} will be thrown.

     * Multicast packets sent with a TTL of {@code 0} are not transmitted

     * on the network but may be delivered locally.

     *

     * @param  ttl

     *         the time-to-live

     *

     * @throws  IOException

     *          if an I/O exception occurs while setting the

     *          default time-to-live value

     *

     * @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)

     */

    @Deprecated

    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} or {@code setNetworkInterface}.

     *

     * <p>If there is a security manager, this method first

     * calls its {@code checkMulticast} method

     * with the {@code mcastaddr} 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} 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");

        }

        checkAddress(mcastaddr, "joinGroup");

        SecurityManager security = System.getSecurityManager();

        if (security != null) {

            security.checkMulticast(mcastaddr);

        }

        if (!mcastaddr.isMulticastAddress()) {

            throw new SocketException("Not a multicast address");

        }

        /**

         * required for some platforms where it's not possible to join

         * a group without setting the interface first.

         */

        NetworkInterface defaultInterface = NetworkInterface.getDefault();

        if (!interfaceSet && defaultInterface != null) {

            setNetworkInterface(defaultInterface);

        }

        getImpl().join(mcastaddr);

    }

    /**

     * Leave a multicast group. Its behavior may be affected by

     * {@code setInterface} or {@code setNetworkInterface}.

     *

     * <p>If there is a security manager, this method first

     * calls its {@code checkMulticast} method

     * with the {@code mcastaddr} 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} 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");

        }

        checkAddress(mcastaddr, "leaveGroup");

        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} method

     * with the {@code mcastaddr} argument

     * as its argument.

     *

     * @param mcastaddr is the multicast address to join

     * @param netIf specifies the local interface to receive multicast

     *        datagram packets, or <i>null</i> to defer to the interface set by

     *       {@link MulticastSocket#setInterface(InetAddress)} or

     *       {@link MulticastSocket#setNetworkInterface(NetworkInterface)}

     *

     * @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} method doesn't allow the join.

     * @throws  IllegalArgumentException if mcastaddr is null or is a

     *          SocketAddress subclass not supported by this socket

     *

     * @see SecurityManager#checkMulticast(InetAddress)

     * @since 1.4

     */

    public void joinGroup(SocketAddress mcastaddr, NetworkInterface netIf)

        throws IOException {

        if (isClosed())

            throw new SocketException("Socket is closed");

        if (mcastaddr == null || !(mcastaddr instanceof InetSocketAddress))

            throw new IllegalArgumentException("Unsupported address type");

        if (oldImpl)

            throw new UnsupportedOperationException();

        checkAddress(((InetSocketAddress)mcastaddr).getAddress(), "joinGroup");

        SecurityManager security = System.getSecurityManager();

        if (security != null) {

            security.checkMulticast(((InetSocketAddress)mcastaddr).getAddress());

        }

        if (!((InetSocketAddress)mcastaddr).getAddress().isMulticastAddress()) {

            throw new SocketException("Not a multicast address");

        }

        getImpl().joinGroup(mcastaddr, netIf);

    }

    /**

     * Leave a multicast group on a specified local interface.

     *

     * <p>If there is a security manager, this method first

     * calls its {@code checkMulticast} method

     * with the {@code mcastaddr} argument

     * as its argument.

     *

     * @param mcastaddr is the multicast address to leave

     * @param netIf specifies the local interface or <i>null</i> to defer

     *             to the interface set by

     *             {@link MulticastSocket#setInterface(InetAddress)} or

     *             {@link MulticastSocket#setNetworkInterface(NetworkInterface)}

     * @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} method doesn't allow the operation.

     * @throws  IllegalArgumentException if mcastaddr is null or is a

     *          SocketAddress subclass not supported by this socket

     *

     * @see SecurityManager#checkMulticast(InetAddress)

     * @since 1.4

     */

    public void leaveGroup(SocketAddress mcastaddr, NetworkInterface netIf)

        throws IOException {

        if (isClosed())

            throw new SocketException("Socket is closed");

        if (mcastaddr == null || !(mcastaddr instanceof InetSocketAddress))

            throw new IllegalArgumentException("Unsupported address type");

        if (oldImpl)

            throw new UnsupportedOperationException();

        checkAddress(((InetSocketAddress)mcastaddr).getAddress(), "leaveGroup");

        SecurityManager security = System.getSecurityManager();

        if (security != null) {

            security.checkMulticast(((InetSocketAddress)mcastaddr).getAddress());

        }

        if (!((InetSocketAddress)mcastaddr).getAddress().isMulticastAddress()) {

            throw new SocketException("Not a multicast address");

        }

        getImpl().leaveGroup(mcastaddr, netIf);

     }

    /**

     * Set the multicast network interface used by methods

     * whose behavior would be affected by the value of the

     * network interface. Useful for multihomed hosts.

     * @param inf the InetAddress

     * @exception SocketException if there is an error in

     * the underlying protocol, such as a TCP error.

     * @see #getInterface()

     */

    public void setInterface(InetAddress inf) throws SocketException {

        if (isClosed()) {

            throw new SocketException("Socket is closed");

        }

        checkAddress(inf, "setInterface");

        synchronized (infLock) {

            getImpl().setOption(SocketOptions.IP_MULTICAST_IF, inf);

            infAddress = inf;

            interfaceSet = true;

        }

    }

    /**

     * Retrieve the address of the network interface used for

     * multicast packets.

     *

     * @return An {@code InetAddress} representing

     *  the address of the network interface used for

     *  multicast packets.

     *

     * @exception SocketException if there is an error in

     * the underlying protocol, such as a TCP error.

     *

     * @see #setInterface(java.net.InetAddress)

     */

    public InetAddress getInterface() throws SocketException {

        if (isClosed()) {

            throw new SocketException("Socket is closed");

        }

        synchronized (infLock) {

            InetAddress ia =

                (InetAddress)getImpl().getOption(SocketOptions.IP_MULTICAST_IF);

            /**

             * No previous setInterface or interface can be

             * set using setNetworkInterface

             */

            if (infAddress == null) {

                return ia;

            }

            /**

             * Same interface set with setInterface?

             */