java/11 : java.base/java/nio/channels/MulticastChannel.java

MulticastChannel
https://openjdk.java.net/
GPLv2 + Classpath Exception
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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.
 IP multicasting is the transmission of IP datagrams to members of
a group that is zero or more hosts identified by a single destination
address.
 In the case of a channel to an IPv4 socket, the underlying operating system optionally supports  RFC 2236: Internet Group
Management Protocol, Version 2 (IGMPv2). When IGMPv2 is supported then
the operating system may additionally support source filtering as specified by
 RFC 3376: Internet Group
Management Protocol, Version 3 (IGMPv3). For channels to an IPv6 socket, the equivalent standards are  RFC 2710:
Multicast Listener Discovery (MLD) for IPv6 and  RFC 3810: Multicast Listener
Discovery Version 2 (MLDv2) for IPv6.
 The 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 interfaces. Membership is dropped by invoking the drop method on the returned MembershipKey. If the underlying platform supports source filtering then the 
block and unblock methods can be used to block or unblock multicast datagrams from particular source addresses. 
 The 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 UnsupportedOperationException if the underlying platform does not support source filtering. Membership is cumulative 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 MembershipKey that represents membership to receive datagrams from the given source address. Invoking the key's drop method drops membership so that datagrams from the source address can no longer be received. 
Platform dependencies
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:

 The creation of the channel should specify the 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 IPv6 socket can join an IPv4 multicast group and receive multicast datagrams sent to the group. 
 The channel's socket should be bound to the 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. 
 The SO_REUSEADDR option should be enabled prior to binding the socket. This is required to allow multiple members of the group to bind to the same address. 

 Usage Example:
    // 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);

Since: 1.7/**
 * 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&nbsp;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&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.
 *
 * <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.
 If the channel is a member of a multicast group then the membership is dropped. Upon return, the membership-key will be 
invalid. 
 This method otherwise behaves exactly as specified by the Channel interface. 
Throws: IOException – 
         If an I/O error occurs/**
     * 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.
 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 source-specific. 
 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.
Params: group – 
         The multicast address to join
interf – 
         The network interface on which to join the group
Throws: IllegalArgumentException –  If the group parameter is not a 
         multicast address, or the group parameter is an address type that is not supported by this channel
IllegalStateException – 
         If the channel already has source-specific membership of the
         group on the interface
UnsupportedOperationException – 
         If the channel's socket is not an Internet Protocol socket, or
         the platform does not support multicasting
ClosedChannelException – 
         If this channel is closed
IOException – 
         If an I/O error occurs
SecurityException –  If a security manager is set, and its checkMulticast method denies access to the multiast group
Returns:  The membership key/**
     * 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 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.
 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 
source-specific. 
 Membership is cumulative 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.
Params: group – 
         The multicast address to join
interf – 
         The network interface on which to join the group
source – 
         The source address
Throws: IllegalArgumentException –  If the group parameter is not a 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
IllegalStateException – 
         If the channel is currently a member of the group on the given
         interface to receive all datagrams
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
ClosedChannelException – 
         If this channel is closed
IOException – 
         If an I/O error occurs
SecurityException –  If a security manager is set, and its checkMulticast method denies access to the multiast group
Returns:  The membership key/**
     * 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 multiast group
     */
    MembershipKey join(InetAddress group, NetworkInterface interf, InetAddress source)
        throws IOException;
}
Params:	group – The multicast address to join interf – The network interface on which to join the group
Throws:	IllegalArgumentException – If the group parameter is not a `multicast` address, or the group parameter is an address type that is not supported by this channel IllegalStateException – If the channel already has source-specific membership of the group on the interface UnsupportedOperationException – If the channel's socket is not an Internet Protocol socket, or the platform does not support multicasting ClosedChannelException – If this channel is closed IOException – If an I/O error occurs SecurityException – If a security manager is set, and its `checkMulticast` method denies access to the multiast group
Returns:	The membership key
/

java/ 11/ java.base/java/nio/channels/MulticastChannel.java

Platform dependencies
