edu.UCL.xmiddle.framework.controller
Class Network

java.lang.Object
  |
  +--edu.UCL.xmiddle.framework.controller.Network

All Implemented Interfaces:

java.lang.Runnable

Direct Known Subclasses:

UDPNetwork

public abstract class Network

extends java.lang.Object

implements java.lang.Runnable

Network.java Network is the basic networking module at the controller core of the xmiddle platform. It provides methods to connect and disconnect to/from the network, send and receive data, negotiate the initiation of protocol sessions and more. Network is also expected to receive protocol requests (e.g. reconciliation requests) from other hosts and service them. Created: Fri Jul 20 13:23:14 2001

Field Summary

protected java.util.Hashtable	activeSessions Contains the active ProtocolChooser sessions, as registered with the registerSession() call
protected Manager	caller Holds a reference to the Manager of the platform.
static boolean	CONNECTED represents the "connected to the network" state
static boolean	DISCONNECTED Represents the "network disconnected" state
protected LocalHost	localhost A reference to the LocalHost object.
protected Locator	locator A reference to the locator object, as set by setLocator()
protected boolean	status The status of the network.

Constructor Summary

Network()

Method Summary

abstract boolean	connect() Connects to the network (and can receive & send data)
abstract Listener	createListener(Host host, java.lang.Object sessionID) Creates and negotiates a Listener object to receive information from the given Host.
abstract Sender	createSender(Host host, java.lang.Object sessionID) Creates and negotiates a Sender object to send information from the given Host.
abstract void	disconnect() Explicitly disconnects from the network
abstract void	exit() Signifies that the platform is about to stop operating.
boolean	getStatus() Returns the connection status of the platform
abstract void	registerSession(ProtocolChooser session) Registers a new ProtocolChooser session.
abstract void	removeSession(java.lang.Object sessionID) Removes a formelly active session from the list of registered sessions.
abstract void	run() What to do when the Network Thread is started.
abstract boolean	send(Data data) Sends the given packet.
void	setLocator(Locator locator) Gives a reference to the local Locator object.

Methods inherited from class java.lang.Object

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

Field Detail

activeSessions

protected java.util.Hashtable activeSessions

Contains the active ProtocolChooser sessions, as registered with the registerSession() call

status

protected boolean status

The status of the network. Either CONNECTED or DISCONNECTED. The implementation is assumed to be responsible for maintaining this value.

caller

protected Manager caller

Holds a reference to the Manager of the platform. Can be used to update status, print debugging info, etc.

locator

protected Locator locator

A reference to the locator object, as set by setLocator()

localhost

protected LocalHost localhost

A reference to the LocalHost object. This can be used to queue protocol requests.

DISCONNECTED

public static boolean DISCONNECTED

Represents the "network disconnected" state

CONNECTED

public static boolean CONNECTED

represents the "connected to the network" state

Constructor Detail

Network

public Network()

Method Detail

connect

public abstract boolean connect()

Connects to the network (and can receive & send data)

Returns:

TRUE if connection is possible and succedded; false otherwise

disconnect

public abstract void disconnect()

Explicitly disconnects from the network

getStatus

public boolean getStatus()

Returns the connection status of the platform

Returns:

CONNECTED or DISCONNECTED

exit

public abstract void exit()

Signifies that the platform is about to stop operating.

send

public abstract boolean send(Data data)

Sends the given packet.

Parameters:

data - The Data packet to send. Note that Data also contains the target Host

Returns:

This is left up to the implementation. it could signify whether the message was sent, or whether it was received and acknowledged etc.

registerSession

public abstract void registerSession(ProtocolChooser session)
                              throws ExistingSessionIDException

Registers a new ProtocolChooser session. Each session must be identified by a unique sessionID. Sessions are registered to the networking layer as to allow:

a) aborting them if the network is disconnected and

b) genetating senders and listeners

Parameters:

session - The ProtocolChooser managing this session

Throws:

ExistingSessionIDException - if a session with the same session ID is already registered.

removeSession

public abstract void removeSession(java.lang.Object sessionID)
                            throws InvalidSessionIDException

Removes a formelly active session from the list of registered sessions. It is assumed that each ProtocolChooser session will de-register itself after finishing.

Parameters:

sessionID - The session's unique ID

Throws:

InvalidSessionIDException - if no session with the given ID is registered

createListener

public abstract Listener createListener(Host host,
                                        java.lang.Object sessionID)

Creates and negotiates a Listener object to receive information from the given Host. The Object is generated for a particular protocol session.

Parameters:

host - The host with which the Listener needs to be negotiated

sessionID - The session ID identifying the session for which this Listener is generated

Returns:

a Listener value

createSender

public abstract Sender createSender(Host host,
                                    java.lang.Object sessionID)

Creates and negotiates a Sender object to send information from the given Host. The Object is generated for a particular protocol session.

Parameters:

host - The host with which the Sender needs to be negotiated

sessionID - The session ID identifying the session for which this Sender is generated

Returns:

a Sender value

setLocator

public void setLocator(Locator locator)

Gives a reference to the local Locator object. This can be used by Network to retreive information on hosts in reach.

Parameters:

locator - The local Locator reference

run

public abstract void run()

What to do when the Network Thread is started. It is assumed that the thread will receive data from the network when we are connected.

Specified by:

run in interface java.lang.Runnable