Back to index...

	/*
	* Copyright (c) 2007, 2013, Oracle and/or its affiliates. All rights reserved.
	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
	*
	* 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.
	*
	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
	* or visit www.oracle.com if you need additional information or have any
	* questions.
	*/

	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
	* datagrams 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();
	}

Back to index...