Class MembershipKey

java.lang.Object
java.nio.channels.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.

Since:
1.7
See Also:

  • Constructor Summary

    Constructors
    Modifier
    Constructor
    Description
    protected
    MembershipKey()
    Initializes a new instance of this class.

  • Method Summary

    Modifier and Type
    Method
    Description
    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.

    Methods declared in class Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
    Modifier and Type
    Method
    Description
    protected Object
    clone()
    Creates and returns a copy of this object.
    boolean
    equals(Object obj)
    Indicates whether some other object is "equal to" this one.
    protected void
    finalize()
    Deprecated, for removal: This API element is subject to removal in a future version.
    Finalization is deprecated and subject to removal in a future release.
    final Class<?>
    getClass()
    Returns the runtime class of this Object.
    int
    hashCode()
    Returns a hash code value for this object.
    final void
    notify()
    Wakes up a single thread that is waiting on this object's monitor.
    final void
    notifyAll()
    Wakes up all threads that are waiting on this object's monitor.
    String
    toString()
    Returns a string representation of the object.
    final void
    wait()
    Causes the current thread to wait until it is awakened, typically by being notified or interrupted.
    final void
    wait(long timeoutMillis)
    Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.
    final void
    wait(long timeoutMillis, int nanos)
    Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.

  • Constructor Details

    • MembershipKey

      protected MembershipKey()
      Initializes a new instance of this class.

  • Method Details

    • isValid

      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

    • drop

      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.

    • block

      public abstract MembershipKey block(InetAddress source) throws IOException
      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

    • unblock

      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

    • channel

      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

    • group

      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

    • networkInterface

      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

    • sourceAddress

      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