The MulticastChannel.java Java example source code
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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.
*
* <p> IP multicasting is the transmission of IP datagrams to members of
* a <em>group 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 supports <a href="http://www.ietf.org/rfc/rfc2236.txt">
* <i>RFC 2236: Internet Group Management Protocol, Version 2 (IGMPv2).
* It may optionally 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>.
* For channels to an {@link StandardProtocolFamily#INET6 IPv6} socket, the equivalent
* standards are <a href="http://www.ietf.org/rfc/rfc2710.txt"> RFC 2710:
* Multicast Listener Discovery (MLD) for IPv6</i> and RFC 3810: Multicast Listener
* Discovery Version 2 (MLDv2) for IPv6</i>.
*
* <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 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
*
* 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> 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>
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>
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>
*
* </ol>
*
* <p> Usage Example:
* <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
* @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.
*
* <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 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.
*
* @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
* @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;
}
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