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MembershipKey

public abstract class MembershipKey
extends Object

java.lang.Object
   ↳ java.nio.channels.MembershipKey


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:

Summary

Protected constructors

MembershipKey()

Initializes a new instance of this class.

Public methods

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 methods

Protected constructors

MembershipKey

added in API level 26
protected MembershipKey ()

Initializes a new instance of this class.

Public methods

block

added in API level 26
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 InetAddress: The source address to block

Returns
MembershipKey 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

channel

added in API level 26
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
MulticastChannel the channel

drop

added in API level 26
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.

group

added in API level 26
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
InetAddress the multicast group

isValid

added in API level 26
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
boolean true if this membership key is valid, false otherwise

networkInterface

added in API level 26
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
NetworkInterface the network interface

sourceAddress

added in API level 26
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
InetAddress The source address if this membership key is source-specific, otherwise null

unblock

added in API level 26
public abstract MembershipKey unblock (InetAddress source)

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

Parameters
source InetAddress: The source address to unblock

Returns
MembershipKey This membership key

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IllegalStateException If the given source address is not currently blocked or the membership key is no longer valid