Class LinkManager

java.lang.Object

org.jcsp.net.LinkManager

All Implemented Interfaces:

CSProcess

class LinkManager
extends Object
implements CSProcess

This class manages the list of open links. It ensures that there is only ever one link between two given JCSP servers.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
private static class	LinkManager.LinkCheck
static class	LinkManager.LinkEstablishmentException
private static class	LinkManager.LinkRequest
private static class	LinkManager.LinksToNodeHolder
private static class	LinkManager.ProfileMatchFailureException

Field Summary

Fields

Modifier and Type	Field	Description
private static final int	ALT_CHECK_FOR_LINK
private static final int	ALT_LINK_FAIL
private static final int	ALT_LOST_LINK
private static final int	ALT_REG_CHAN
private static final int	ALT_REQ_LINK
private final Any2OneChannel	checkForLink
private final Any2OneChannel	getNodeIDChan
private static LinkManager	instance
private final Any2OneChannel	linkFailureChan
private Hashtable	linkHolders	The active links.
private LoopbackLink	loopbackLink	The LoopBackLink used for local connections.
private final Any2OneChannel	lostLinkChan
private final Any2OneConnection	registerConn
private final Any2OneChannel	registerEventChannel
private final Any2OneChannel	requestLink

Constructor Summary

Constructors

Constructor	Description
LinkManager()

Method Summary

Modifier and Type	Method	Description
(package private) static LinkManager	getInstance()	Get the singleton instance of LinkManager.
private Link	getLink(NodeID target, Profile linkProfile)	Get a Link to a remote PC.
(package private) AltingChannelInput	getLinkLostEventChannel()
(package private) ChannelOutput	getTxChannel(NodeAddressID targetAddress)	This is used to get a Link when no details are known about the other Node except for one of its addresses.
(package private) ChannelOutput	getTxChannel(NodeID target)	Get a channel to use to send to a remote PC.
(package private) ChannelOutput	getTxChannel(NodeID target, Profile linkProfile)
(package private) boolean	linkExists(NodeID otherNode)	This method tests whether a link exists to a specified remote Node in this LinkManager.
(package private) int	lostLink(Link conn)	Called by a Link to indicate the link broke.
(package private) void	registerFailure(Link conn)
(package private) boolean	registerLink(Link conn)	Register a Link in the database.
void	run()	Used to run the LinkManager.
void	start()	Starts this instance of the LinkManager and returns.

Methods inherited from class Object

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

Field Details

instance

private static LinkManager instance

linkHolders

private Hashtable linkHolders

The active links. This is a hashtable where the key is a NodeID and the value is a Link.

See Also:

• NodeID
• Link

loopbackLink

private LoopbackLink loopbackLink

The LoopBackLink used for local connections.

registerConn

private final Any2OneConnection registerConn

requestLink

private final Any2OneChannel requestLink

lostLinkChan

private final Any2OneChannel lostLinkChan

linkFailureChan

private final Any2OneChannel linkFailureChan

checkForLink

private final Any2OneChannel checkForLink

getNodeIDChan

private final Any2OneChannel getNodeIDChan

registerEventChannel

private final Any2OneChannel registerEventChannel

ALT_LOST_LINK

private static final int ALT_LOST_LINK

See Also:

• Constant Field Values

ALT_LINK_FAIL

private static final int ALT_LINK_FAIL

See Also:

• Constant Field Values

ALT_REG_CHAN

private static final int ALT_REG_CHAN

See Also:

• Constant Field Values

ALT_REQ_LINK

private static final int ALT_REQ_LINK

See Also:

• Constant Field Values

ALT_CHECK_FOR_LINK

private static final int ALT_CHECK_FOR_LINK

See Also:

• Constant Field Values

Constructor Details

LinkManager

LinkManager()

Method Details

run

public void run()

Used to run the LinkManager.

Specified by:

run in interface CSProcess

start

public void start()

Starts this instance of the LinkManager and returns.

getInstance

static LinkManager getInstance()

Get the singleton instance of LinkManager.

Returns:

The singleton LinkManager object.

registerLink

boolean registerLink(Link conn)

Register a Link in the database. Prevents duplicates. Returns true if there was no prior entry for that NodeID, and one was added. (In that case it has also notified any waiting processes). Returns false (and does not change the database) if there is an existing entry.

Returns:

true iff there was no prior entry for that NodeID

registerFailure

void registerFailure(Link conn)

getTxChannel

ChannelOutput getTxChannel(NodeID target)

Get a channel to use to send to a remote PC. Will block (possibly forever) while the link is being established.

Parameters:

target - The system to connect to.

Returns:

The Channel to use to send to the requested computer.

Throws:

IllegalStateException - If init() has not been called.

getTxChannel

ChannelOutput getTxChannel(NodeID target,
 Profile linkProfile)

getTxChannel

ChannelOutput getTxChannel(NodeAddressID targetAddress)

This is used to get a Link when no details are known about the other Node except for one of its addresses. A typical situation when this would be used is to connect to the CNS.

Parameters:

targetAddress - The address to which to create a link.

Returns:

the ChannelOuput that writes to the link.

getLink

private Link getLink(NodeID target,
 Profile linkProfile)

Get a Link to a remote PC. Will block (possibly forever) while the link is being established.

Parameters:

target - The system to connect to.

Returns:

The Link to the requested computer.

Throws:

IllegalStateException - If init() has not been called.

lostLink

int lostLink(Link conn)

Called by a Link to indicate the link broke.

Parameters:

conn - The broken link.

linkExists

boolean linkExists(NodeID otherNode)

This method tests whether a link exists to a specified remote Node in this LinkManager.

Parameters:

otherNode - The NodeID of a remote Node to check the existance

Returns:

true iff a link currently exists to the specified remote Node.

getLinkLostEventChannel

AltingChannelInput getLinkLostEventChannel()