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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
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* 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.nio.channels;
import java.net.InetAddress;
import java.net.NetworkInterface;
import java.io.IOException;
/**
* A token representing the membership of an Internet Protocol (IP) multicast
* group.
*
* <p> A membership key may represent a membership to receive all datagrams sent
* to the group, or it may be <em>source-specific</em>, meaning that it
* represents a membership that receives only datagrams from a specific source
* address. Whether or not a membership key is source-specific may be determined
* by invoking its {@link #sourceAddress() sourceAddress} method.
*
* <p> A membership key is valid upon creation and remains valid until the
* membership is dropped by invoking the {@link #drop() drop} method, or
* the channel is closed. The validity of the membership key may be tested
* by invoking its {@link #isValid() isValid} method.
*
* <p> Where a membership key is not source-specific and the underlying operation
* system supports source filtering, then the {@link #block block} and {@link
* #unblock unblock} methods can be used to block or unblock multicast datagrams
* from particular source addresses.
*
* @see MulticastChannel
*
* @since 1.7
*/
public abstract class MembershipKey {
/**
* Initializes a new instance of this class.
*/
protected MembershipKey() {
}
/**
* Tells whether or not this membership is valid.
*
* <p> A multicast group membership is valid upon creation and remains
* valid until the membership is dropped by invoking the {@link #drop() drop}
* method, or the channel is closed.
*
* @return {@code true} if this membership key is valid, {@code false}
* otherwise
*/
public abstract boolean isValid();
/**
* Drop membership.
*
* <p> If the membership key represents a membership to receive all datagrams
* then the membership is dropped and the channel will no longer receive any
* datagrams sent to the group. If the membership key is source-specific
* then the channel will no longer receive datagrams sent to the group from
* that source address.
*
* <p> After membership is dropped it may still be possible to receive
* datagrams sent to the group. This can arise when datagrams are waiting to
* be received in the socket's receive buffer. After membership is dropped
* then the channel may {@link MulticastChannel#join join} the group again
* in which case a new membership key is returned.
*
* <p> Upon return, this membership object will be {@link #isValid() invalid}.
* If the multicast group membership is already invalid then invoking this
* method has no effect. Once a multicast group membership is invalid,
* it remains invalid forever.
*/
public abstract void drop();
/**
* Block multicast datagrams from the given source address.
*
* <p> If this membership key is not source-specific, and the underlying
* operating system supports source filtering, then this method blocks
* multicast datagrams from the given source address. If the given source
* address is already blocked then this method has no effect.
* After a source address is blocked it may still be possible to receive
* datagams from that source. This can arise when datagrams are waiting to
* be received in the socket's receive buffer.
*
* @param source
* The source address to block
*
* @return This membership key
*
* @throws IllegalArgumentException
* If the {@code source} parameter is not a unicast address or
* is not the same address type as the multicast group
* @throws IllegalStateException
* If this membership key is source-specific or is no longer valid
* @throws UnsupportedOperationException
* If the underlying operating system does not support source
* filtering
* @throws IOException
* If an I/O error occurs
*/
public abstract MembershipKey block(InetAddress source) throws IOException;
/**
* Unblock multicast datagrams from the given source address that was
* previously blocked using the {@link #block(InetAddress) block} method.
*
* @param source
* The source address to unblock
*
* @return This membership key
*
* @throws IllegalStateException
* If the given source address is not currently blocked or the
* membership key is no longer valid
*/
public abstract MembershipKey unblock(InetAddress source);
/**
* Returns the channel for which this membership key was created. This
* method will continue to return the channel even after the membership
* becomes {@link #isValid invalid}.
*
* @return the channel
*/
public abstract MulticastChannel channel();
/**
* Returns the multicast group for which this membership key was created.
* This method will continue to return the group even after the membership
* becomes {@link #isValid invalid}.
*
* @return the multicast group
*/
public abstract InetAddress group();
/**
* Returns the network interface for which this membership key was created.
* This method will continue to return the network interface even after the
* membership becomes {@link #isValid invalid}.
*
* @return the network interface
*/
public abstract NetworkInterface networkInterface();
/**
* Returns the source address if this membership key is source-specific,
* or {@code null} if this membership is not source-specific.
*
* @return The source address if this membership key is source-specific,
* otherwise {@code null}
*/
public abstract InetAddress sourceAddress();
}