Java tutorial
/* * 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; 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 optionally supports * <a href="http://www.ietf.org/rfc/rfc2236.txt"> <i>RFC 2236: Internet Group * Management Protocol, Version 2 (IGMPv2)</i></a>. When IGMPv2 is supported then * the operating system may additionally support source filtering as specified by * <a href="http://www.ietf.org/rfc/rfc3376.txt"> <i>RFC 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 2710: * Multicast Listener Discovery (MLD) for IPv6</i></a> and <a * href="http://www.ietf.org/rfc/rfc3810.txt"> <i>RFC 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. * * <h2>Platform dependencies</h2> * * 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, or * the platform does not support multicasting * @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 multicast 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, or the platform does not * support multicasting * @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 multicast group */ MembershipKey join(InetAddress group, NetworkInterface interf, InetAddress source) throws IOException; }