1 /* 2 * Copyright (c) 2007, 2013, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. Oracle designates this 8 * particular file as subject to the "Classpath" exception as provided 9 * by Oracle in the LICENSE file that accompanied this code. 10 * 11 * This code is distributed in the hope that it will be useful, but WITHOUT 12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 14 * version 2 for more details (a copy is included in the LICENSE file that 15 * accompanied this code). 16 * 17 * You should have received a copy of the GNU General Public License version 18 * 2 along with this work; if not, write to the Free Software Foundation, 19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 20 * 21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 22 * or visit www.oracle.com if you need additional information or have any 23 * questions. 24 */ 25 26 package java.nio.channels; 27 28 import java.net.InetAddress; 29 import java.net.NetworkInterface; 30 import java.io.IOException; 31 import java.net.ProtocolFamily; // javadoc 32 import java.net.StandardProtocolFamily; // javadoc 33 import java.net.StandardSocketOptions; // javadoc 34 35 /** 36 * A network channel that supports Internet Protocol (IP) multicasting. 37 * 38 * <p> IP multicasting is the transmission of IP datagrams to members of 39 * a <em>group</em> that is zero or more hosts identified by a single destination 40 * address. 41 * 42 * <p> In the case of a channel to an {@link StandardProtocolFamily#INET IPv4} socket, 43 * the underlying operating system supports <a href="http://www.ietf.org/rfc/rfc2236.txt"> 44 * <i>RFC 2236: Internet Group Management Protocol, Version 2 (IGMPv2)</i></a>. 45 * It may optionally support source filtering as specified by <a 46 * href="http://www.ietf.org/rfc/rfc3376.txt"> <i>RFC 3376: Internet Group 47 * Management Protocol, Version 3 (IGMPv3)</i></a>. 48 * For channels to an {@link StandardProtocolFamily#INET6 IPv6} socket, the equivalent 49 * standards are <a href="http://www.ietf.org/rfc/rfc2710.txt"> <i>RFC 2710: 50 * Multicast Listener Discovery (MLD) for IPv6</i></a> and <a 51 * href="http://www.ietf.org/rfc/rfc3810.txt"> <i>RFC 3810: Multicast Listener 52 * Discovery Version 2 (MLDv2) for IPv6</i></a>. 53 * 54 * <p> The {@link #join(InetAddress,NetworkInterface)} method is used to 55 * join a group and receive all multicast datagrams sent to the group. A channel 56 * may join several multicast groups and may join the same group on several 57 * {@link NetworkInterface interfaces}. Membership is dropped by invoking the {@link 58 * MembershipKey#drop drop} method on the returned {@link MembershipKey}. If the 59 * underlying platform supports source filtering then the {@link MembershipKey#block 60 * block} and {@link MembershipKey#unblock unblock} methods can be used to block or 61 * unblock multicast datagrams from particular source addresses. 62 * 63 * <p> The {@link #join(InetAddress,NetworkInterface,InetAddress)} method 64 * is used to begin receiving datagrams sent to a group whose source address matches 65 * a given source address. This method throws {@link UnsupportedOperationException} 66 * if the underlying platform does not support source filtering. Membership is 67 * <em>cumulative</em> and this method may be invoked again with the same group 68 * and interface to allow receiving datagrams from other source addresses. The 69 * method returns a {@link MembershipKey} that represents membership to receive 70 * datagrams from the given source address. Invoking the key's {@link 71 * MembershipKey#drop drop} method drops membership so that datagrams from the 72 * source address can no longer be received. 73 * 74 * <h2>Platform dependencies</h2> 75 * 76 * The multicast implementation is intended to map directly to the native 77 * multicasting facility. Consequently, the following items should be considered 78 * when developing an application that receives IP multicast datagrams: 79 * 80 * <ol> 81 * 82 * <li><p> The creation of the channel should specify the {@link ProtocolFamily} 83 * that corresponds to the address type of the multicast groups that the channel 84 * will join. There is no guarantee that a channel to a socket in one protocol 85 * family can join and receive multicast datagrams when the address of the 86 * multicast group corresponds to another protocol family. For example, it is 87 * implementation specific if a channel to an {@link StandardProtocolFamily#INET6 IPv6} 88 * socket can join an {@link StandardProtocolFamily#INET IPv4} multicast group and receive 89 * multicast datagrams sent to the group. </p></li> 90 * 91 * <li><p> The channel's socket should be bound to the {@link 92 * InetAddress#isAnyLocalAddress wildcard} address. If the socket is bound to 93 * a specific address, rather than the wildcard address then it is implementation 94 * specific if multicast datagrams are received by the socket. </p></li> 95 * 96 * <li><p> The {@link StandardSocketOptions#SO_REUSEADDR SO_REUSEADDR} option should be 97 * enabled prior to {@link NetworkChannel#bind binding} the socket. This is 98 * required to allow multiple members of the group to bind to the same 99 * address. </p></li> 100 * 101 * </ol> 102 * 103 * <p> <b>Usage Example:</b> 104 * <pre> 105 * // join multicast group on this interface, and also use this 106 * // interface for outgoing multicast datagrams 107 * NetworkInterface ni = NetworkInterface.getByName("hme0"); 108 * 109 * DatagramChannel dc = DatagramChannel.open(StandardProtocolFamily.INET) 110 * .setOption(StandardSocketOptions.SO_REUSEADDR, true) 111 * .bind(new InetSocketAddress(5000)) 112 * .setOption(StandardSocketOptions.IP_MULTICAST_IF, ni); 113 * 114 * InetAddress group = InetAddress.getByName("225.4.5.6"); 115 * 116 * MembershipKey key = dc.join(group, ni); 117 * </pre> 118 * 119 * @since 1.7 120 */ 121 122 public interface MulticastChannel 123 extends NetworkChannel 124 { 125 /** 126 * Closes this channel. 127 * 128 * <p> If the channel is a member of a multicast group then the membership 129 * is {@link MembershipKey#drop dropped}. Upon return, the {@link 130 * MembershipKey membership-key} will be {@link MembershipKey#isValid 131 * invalid}. 132 * 133 * <p> This method otherwise behaves exactly as specified by the {@link 134 * Channel} interface. 135 * 136 * @throws IOException 137 * If an I/O error occurs 138 */ 139 @Override void close() throws IOException; 140 141 /** 142 * Joins a multicast group to begin receiving all datagrams sent to the group, 143 * returning a membership key. 144 * 145 * <p> If this channel is currently a member of the group on the given 146 * interface to receive all datagrams then the membership key, representing 147 * that membership, is returned. Otherwise this channel joins the group and 148 * the resulting new membership key is returned. The resulting membership key 149 * is not {@link MembershipKey#sourceAddress source-specific}. 150 * 151 * <p> A multicast channel may join several multicast groups, including 152 * the same group on more than one interface. An implementation may impose a 153 * limit on the number of groups that may be joined at the same time. 154 * 155 * @param group 156 * The multicast address to join 157 * @param interf 158 * The network interface on which to join the group 159 * 160 * @return The membership key 161 * 162 * @throws IllegalArgumentException 163 * If the group parameter is not a {@link InetAddress#isMulticastAddress 164 * multicast} address, or the group parameter is an address type 165 * that is not supported by this channel 166 * @throws IllegalStateException 167 * If the channel already has source-specific membership of the 168 * group on the interface 169 * @throws UnsupportedOperationException 170 * If the channel's socket is not an Internet Protocol socket 171 * @throws ClosedChannelException 172 * If this channel is closed 173 * @throws IOException 174 * If an I/O error occurs 175 * @throws SecurityException 176 * If a security manager is set, and its 177 * {@link SecurityManager#checkMulticast(InetAddress) checkMulticast} 178 * method denies access to the multiast group 179 */ 180 MembershipKey join(InetAddress group, NetworkInterface interf) 181 throws IOException; 182 183 /** 184 * Joins a multicast group to begin receiving datagrams sent to the group 185 * from a given source address. 186 * 187 * <p> If this channel is currently a member of the group on the given 188 * interface to receive datagrams from the given source address then the 189 * membership key, representing that membership, is returned. Otherwise this 190 * channel joins the group and the resulting new membership key is returned. 191 * The resulting membership key is {@link MembershipKey#sourceAddress 192 * source-specific}. 193 * 194 * <p> Membership is <em>cumulative</em> and this method may be invoked 195 * again with the same group and interface to allow receiving datagrams sent 196 * by other source addresses to the group. 197 * 198 * @param group 199 * The multicast address to join 200 * @param interf 201 * The network interface on which to join the group 202 * @param source 203 * The source address 204 * 205 * @return The membership key 206 * 207 * @throws IllegalArgumentException 208 * If the group parameter is not a {@link 209 * InetAddress#isMulticastAddress multicast} address, the 210 * source parameter is not a unicast address, the group 211 * parameter is an address type that is not supported by this channel, 212 * or the source parameter is not the same address type as the group 213 * @throws IllegalStateException 214 * If the channel is currently a member of the group on the given 215 * interface to receive all datagrams 216 * @throws UnsupportedOperationException 217 * If the channel's socket is not an Internet Protocol socket or 218 * source filtering is not supported 219 * @throws ClosedChannelException 220 * If this channel is closed 221 * @throws IOException 222 * If an I/O error occurs 223 * @throws SecurityException 224 * If a security manager is set, and its 225 * {@link SecurityManager#checkMulticast(InetAddress) checkMulticast} 226 * method denies access to the multiast group 227 */ 228 MembershipKey join(InetAddress group, NetworkInterface interf, InetAddress source) 229 throws IOException; 230 } 231
