MembershipKey

public abstract class MembershipKey extends Object

A token representing the membership of an Internet Protocol (IP) multicast group.

A membership key may represent a membership to receive all datagrams sent to the group, or it may be source-specific, 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 sourceAddress method.

A membership key is valid upon creation and remains valid until the membership is dropped by invoking the drop method, or the channel is closed. The validity of the membership key may be tested by invoking its isValid method.

Where a membership key is not source-specific and the underlying operation system supports source filtering, then the block and unblock methods can be used to block or unblock multicast datagrams from particular source addresses.

See Also

• MulticastChannel

Protected Constructor Summary

MembershipKey() Initializes a new instance of this class.

Public Method Summary

abstract MembershipKey	block(InetAddress source) Block multicast datagrams from the given source address.
abstract MulticastChannel	channel() Returns the channel for which this membership key was created.
abstract void	drop() Drop membership.
abstract InetAddress	group() Returns the multicast group for which this membership key was created.
abstract boolean	isValid() Tells whether or not this membership is valid.
abstract NetworkInterface	networkInterface() Returns the network interface for which this membership key was created.
abstract InetAddress	sourceAddress() Returns the source address if this membership key is source-specific, or null if this membership is not source-specific.
abstract MembershipKey	unblock(InetAddress source) Unblock multicast datagrams from the given source address that was previously blocked using the block method.

Inherited Method Summary

From class java.lang.Object

Object	clone() Creates and returns a copy of this Object.
boolean	equals(Object obj) Compares this instance with the specified object and indicates if they are equal.
void	finalize() Invoked when the garbage collector has detected that this instance is no longer reachable.
final Class<?>	getClass() Returns the unique instance of Class that represents this object's class.
int	hashCode() Returns an integer hash code for this object.
final void	notify() Causes a thread which is waiting on this object's monitor (by means of calling one of the wait() methods) to be woken up.
final void	notifyAll() Causes all threads which are waiting on this object's monitor (by means of calling one of the wait() methods) to be woken up.
String	toString() Returns a string containing a concise, human-readable description of this object.
final void	wait(long timeout, int nanos) Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object or until the specified timeout expires.
final void	wait(long timeout) Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object or until the specified timeout expires.
final void	wait() Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object.

Protected Constructors

protected MembershipKey ()

Initializes a new instance of this class.

Public Methods

public abstract MembershipKey block (InetAddress source)

Block multicast datagrams from the given source address.

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.

Parameters

source	The source address to block

Returns

• This membership key

Throws

IllegalArgumentException	If the source parameter is not a unicast address or is not the same address type as the multicast group
IllegalStateException	If this membership key is source-specific or is no longer valid
UnsupportedOperationException	If the underlying operating system does not support source filtering
IOException	If an I/O error occurs

public abstract MulticastChannel channel ()

Returns the channel for which this membership key was created. This method will continue to return the channel even after the membership becomes invalid.

Returns

• the channel

public abstract void drop ()

Drop membership.

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.

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 join the group again in which case a new membership key is returned.

Upon return, this membership object will be 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 InetAddress group ()

Returns the multicast group for which this membership key was created. This method will continue to return the group even after the membership becomes invalid.

Returns

• the multicast group

public abstract boolean isValid ()

Tells whether or not this membership is valid.

A multicast group membership is valid upon creation and remains valid until the membership is dropped by invoking the drop method, or the channel is closed.

Returns

• true if this membership key is valid, false otherwise

public abstract NetworkInterface networkInterface ()

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 invalid.

Returns

• the network interface

public abstract InetAddress sourceAddress ()

Returns the source address if this membership key is source-specific, or null if this membership is not source-specific.

Returns

• The source address if this membership key is source-specific, otherwise null

public abstract MembershipKey unblock (InetAddress source)

Unblock multicast datagrams from the given source address that was previously blocked using the block method.

Parameters

source	The source address to unblock

Returns

• This membership key

Throws

IllegalStateException	If the given source address is not currently blocked or the membership key is no longer valid