mcast
Class TOMCastSocket

java.lang.Object
  mcast.MCastSocket
      mcast.TOMCastSocket

All Implemented Interfaces:

java.lang.Runnable

public class TOMCastSocket
extends MCastSocket
implements java.lang.Runnable

TOMCastSocket implements total ordering, on top of an MCastSocket, which provides (unordered) multicast.

Version:

$Id: TOMCastSocket.java,v 1.2 2009/01/13 05:36:20 zahorjan Exp $

Field Summary

private int	BUFFER_SIZE A not-very-respected limit on the number of packets to be buffered.
private int	clock Our Lamport clock.
private boolean	drained Set to true once there are no more packets in the receive queue and there will never be any again.
private java.util.concurrent.ArrayBlockingQueue<TOMCastPacket>	inComingPktBuf The ordered queue of packets to be given to the caller of receive().
private java.lang.Thread	receiver A TOMCastSocket uses a separate thread on the receive side.

Fields inherited from class mcast.MCastSocket

CLOSED, CONNECTED, DRAINED, STARTING

Constructor Summary

TOMCastSocket()
Create a TOMCastSock socket at an ephemeral port.

Method Summary

private int	incrementClock() This is one of two routines that updates the clock in a thread safe way.
TOMCastPacket	receive() Receive blocks if nothing is available right now.
void	run() This is the receive thread loop, invoked when the thread is started.
void	send(TOMCastPacket pkt) This is multicast send.
private int	updateClockWithMax(int otherVal) This is one of two routines that updates the clock in a thread safe way.

Methods inherited from class mcast.MCastSocket

getClientId, getMCastGroupSize, join, leave, send

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

receiver

private java.lang.Thread receiver

A TOMCastSocket uses a separate thread on the receive side. That thread fetches packets from the underlying MCastSocket, buffers them as necesssary to achieve the total ordering property, and eventually puts them in a receive queue for the client to find on receive() calls.

inComingPktBuf

private java.util.concurrent.ArrayBlockingQueue<TOMCastPacket> inComingPktBuf

The ordered queue of packets to be given to the caller of receive(). It's synchronized because there may be concurrent injections of packets (by our receive thread) and removals (by the user thread calling receive).

BUFFER_SIZE

private final int BUFFER_SIZE

A not-very-respected limit on the number of packets to be buffered. Don't worry too much about enforcing this. It's here just in case we want to induce some packet losses, out of curiosity - we set it small.

See Also:

Constant Field Values

drained

private boolean drained

Set to true once there are no more packets in the receive queue and there will never be any again.

clock

private int clock

Our Lamport clock.

Constructor Detail

TOMCastSocket

public TOMCastSocket()
              throws java.net.SocketException

Create a TOMCastSock socket at an ephemeral port.

Throws:

java.net.SocketException

Method Detail

receive

public TOMCastPacket receive()

Receive blocks if nothing is available right now.

Overrides:

receive in class MCastSocket

Returns:

Next packet, in order. If none will ever be available again, returns null.

send

public void send(TOMCastPacket pkt)
          throws java.io.IOException

This is multicast send. It is non-blocking (we don't (and can't) wait until the data arrives at the other end before returning to the caller).

Throws:

java.io.IOException

updateClockWithMax

private int updateClockWithMax(int otherVal)

This is one of two routines that updates the clock in a thread safe way. This one implements:
clock = max(clock,otherVal)+1

Parameters:

otherVal - Some value.

Returns:

The old value of the clock.

incrementClock

private int incrementClock()

This is one of two routines that updates the clock in a thread safe way. This one does:
clock++

Returns:

the old value of the clock.

run

public void run()

This is the receive thread loop, invoked when the thread is started.

Specified by:

run in interface java.lang.Runnable