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package java.nio.channels;

import java.net.InetAddress;

import java.net.NetworkInterface;

import java.io.IOException;

import java.net.ProtocolFamily;             // javadoc

import java.net.StandardProtocolFamily;     // javadoc

import java.net.StandardSocketOptions;      // javadoc

/**

 * A network channel that supports Internet Protocol (IP) multicasting.

 *

 * <p> IP multicasting is the transmission of IP datagrams to members of

 * a <em>group</em> that is zero or more hosts identified by a single destination

 * address.

 *

 * <p> In the case of a channel to an {@link StandardProtocolFamily#INET IPv4} socket,

 * the underlying operating system supports <a href="http://www.ietf.org/rfc/rfc2236.txt">

 * <i>RFC&nbsp;2236: Internet Group Management Protocol, Version 2 (IGMPv2)</i></a>.

 * It may optionally support source filtering as specified by <a

 * href="http://www.ietf.org/rfc/rfc3376.txt"> <i>RFC&nbsp;3376: Internet Group

 * Management Protocol, Version 3 (IGMPv3)</i></a>.

 * For channels to an {@link StandardProtocolFamily#INET6 IPv6} socket, the equivalent

 * standards are <a href="http://www.ietf.org/rfc/rfc2710.txt"> <i>RFC&nbsp;2710:

 * Multicast Listener Discovery (MLD) for IPv6</i></a> and <a

 * href="http://www.ietf.org/rfc/rfc3810.txt"> <i>RFC&nbsp;3810: Multicast Listener

 * Discovery Version 2 (MLDv2) for IPv6</i></a>.

 *

 * <p> The {@link #join(InetAddress,NetworkInterface)} method is used to

 * join a group and receive all multicast datagrams sent to the group. A channel

 * may join several multicast groups and may join the same group on several

 * {@link NetworkInterface interfaces}. Membership is dropped by invoking the {@link

 * MembershipKey#drop drop} method on the returned {@link MembershipKey}. If the

 * underlying platform supports source filtering then the {@link MembershipKey#block

 * block} and {@link MembershipKey#unblock unblock} methods can be used to block or

 * unblock multicast datagrams from particular source addresses.

 *

 * <p> The {@link #join(InetAddress,NetworkInterface,InetAddress)} method

 * is used to begin receiving datagrams sent to a group whose source address matches

 * a given source address. This method throws {@link UnsupportedOperationException}

 * if the underlying platform does not support source filtering.  Membership is

 * <em>cumulative</em> and this method may be invoked again with the same group

 * and interface to allow receiving datagrams from other source addresses. The

 * method returns a {@link MembershipKey} that represents membership to receive

 * datagrams from the given source address. Invoking the key's {@link

 * MembershipKey#drop drop} method drops membership so that datagrams from the

 * source address can no longer be received.

 *

 * <h4>Platform dependencies</h4>

 *

 * The multicast implementation is intended to map directly to the native

 * multicasting facility. Consequently, the following items should be considered

 * when developing an application that receives IP multicast datagrams:

 *

 * <ol>

 *

 * <li><p> The creation of the channel should specify the {@link ProtocolFamily}

 * that corresponds to the address type of the multicast groups that the channel

 * will join. There is no guarantee that a channel to a socket in one protocol

 * family can join and receive multicast datagrams when the address of the

 * multicast group corresponds to another protocol family. For example, it is

 * implementation specific if a channel to an {@link StandardProtocolFamily#INET6 IPv6}

 * socket can join an {@link StandardProtocolFamily#INET IPv4} multicast group and receive

 * multicast datagrams sent to the group. </p></li>

 *

 * <li><p> The channel's socket should be bound to the {@link

 * InetAddress#isAnyLocalAddress wildcard} address. If the socket is bound to

 * a specific address, rather than the wildcard address then it is implementation

 * specific if multicast datagrams are received by the socket. </p></li>

 *

 * <li><p> The {@link StandardSocketOptions#SO_REUSEADDR SO_REUSEADDR} option should be

 * enabled prior to {@link NetworkChannel#bind binding} the socket. This is

 * required to allow multiple members of the group to bind to the same

 * address. </p></li>

 *

 * </ol>

 *

 * <p> <b>Usage Example:</b>

 * <pre>

 *     // join multicast group on this interface, and also use this

 *     // interface for outgoing multicast datagrams

 *     NetworkInterface ni = NetworkInterface.getByName("hme0");

 *

 *     DatagramChannel dc = DatagramChannel.open(StandardProtocolFamily.INET)

 *         .setOption(StandardSocketOptions.SO_REUSEADDR, true)

 *         .bind(new InetSocketAddress(5000))

 *         .setOption(StandardSocketOptions.IP_MULTICAST_IF, ni);

 *

 *     InetAddress group = InetAddress.getByName("225.4.5.6");

 *

 *     MembershipKey key = dc.join(group, ni);

 * </pre>

 *

 * @since 1.7

 */

public interface MulticastChannel

    extends NetworkChannel

{

    /**

     * Closes this channel.

     *

     * <p> If the channel is a member of a multicast group then the membership

     * is {@link MembershipKey#drop dropped}. Upon return, the {@link

     * MembershipKey membership-key} will be {@link MembershipKey#isValid

     * invalid}.

     *

     * <p> This method otherwise behaves exactly as specified by the {@link

     * Channel} interface.

     *

     * @throws  IOException

     *          If an I/O error occurs

     */

    @Override void close() throws IOException;

    /**

     * Joins a multicast group to begin receiving all datagrams sent to the group,

     * returning a membership key.

     *

     * <p> If this channel is currently a member of the group on the given

     * interface to receive all datagrams then the membership key, representing

     * that membership, is returned. Otherwise this channel joins the group and

     * the resulting new membership key is returned. The resulting membership key

     * is not {@link MembershipKey#sourceAddress source-specific}.

     *

     * <p> A multicast channel may join several multicast groups, including

     * the same group on more than one interface. An implementation may impose a

     * limit on the number of groups that may be joined at the same time.

     *

     * @param   group

     *          The multicast address to join

     * @param   interf

     *          The network interface on which to join the group

     *

     * @return  The membership key

     *

     * @throws  IllegalArgumentException

     *          If the group parameter is not a {@link InetAddress#isMulticastAddress

     *          multicast} address, or the group parameter is an address type

     *          that is not supported by this channel

     * @throws  IllegalStateException

     *          If the channel already has source-specific membership of the

     *          group on the interface

     * @throws  UnsupportedOperationException

     *          If the channel's socket is not an Internet Protocol socket

     * @throws  ClosedChannelException

     *          If this channel is closed

     * @throws  IOException

     *          If an I/O error occurs

     * @throws  SecurityException

     *          If a security manager is set, and its

     *          {@link SecurityManager#checkMulticast(InetAddress) checkMulticast}

     *          method denies access to the multiast group

     */

    MembershipKey join(InetAddress group, NetworkInterface interf)

        throws IOException;

    /**

     * Joins a multicast group to begin receiving datagrams sent to the group

     * from a given source address.

     *

     * <p> If this channel is currently a member of the group on the given

     * interface to receive datagrams from the given source address then the

     * membership key, representing that membership, is returned. Otherwise this

     * channel joins the group and the resulting new membership key is returned.

     * The resulting membership key is {@link MembershipKey#sourceAddress

     * source-specific}.

     *

     * <p> Membership is <em>cumulative</em> and this method may be invoked

     * again with the same group and interface to allow receiving datagrams sent

     * by other source addresses to the group.

     *

     * @param   group

     *          The multicast address to join

     * @param   interf

     *          The network interface on which to join the group

     * @param   source

     *          The source address

     *

     * @return  The membership key

     *

     * @throws  IllegalArgumentException

     *          If the group parameter is not a {@link

     *          InetAddress#isMulticastAddress multicast} address, the

     *          source parameter is not a unicast address, the group

     *          parameter is an address type that is not supported by this channel,

     *          or the source parameter is not the same address type as the group

     * @throws  IllegalStateException

     *          If the channel is currently a member of the group on the given

     *          interface to receive all datagrams

     * @throws  UnsupportedOperationException

     *          If the channel's socket is not an Internet Protocol socket or

     *          source filtering is not supported

     * @throws  ClosedChannelException

     *          If this channel is closed

     * @throws  IOException

     *          If an I/O error occurs

     * @throws  SecurityException

     *          If a security manager is set, and its

     *          {@link SecurityManager#checkMulticast(InetAddress) checkMulticast}

     *          method denies access to the multiast group

     */

    MembershipKey join(InetAddress group, NetworkInterface interf, InetAddress source)

        throws IOException;

}