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com.synaptics.elvis
Class ElvisComm  

java.lang.Object
  com.synaptics.elvis.ElvisComm

All Implemented Interfaces:

java.lang.Runnable

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final class ElvisComm

extends java.lang.Object

implements java.lang.Runnable

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Field Summary
private  java.io.File	auth
private  ElvisMessageFactory	emf           This guy puts together messages for us to send to another Elvis, either requests to be sent to the One True Elvis, or responses to be sent back to a client.
private  ElvisHandler	handler           This is the Elvis handler provided by the client.
private  java.lang.String	key
static int	MAX_PORT_OFFSET           A random number between this 0 and this value will be added to the port number submitted by the user.
static int	MAX_SERVER_PORT           The maximum possible port number is 65535.
static int	MIN_SERVER_PORT           This value is chosen to prevent collisions with the so called "well known" ports like ftp, telnet, etc.
private  int	port
private  java.lang.String	program           This is the name of the program, as supplied by the user.
private  java.beans.PropertyChangeSupport	propertyChangeSupport           Utility field used by bound properties.
private  java.net.ServerSocket	server
private static java.lang.String	SETTINGS_DIRECTORY           This is where we keep the file with the public information about Elvis.
private  ElvisCommStatus	status           This is the status of the Listener.
static java.lang.String	STATUS_PROPERTY
private  int	theActualPort           This is the actual port value we are listening to.
private  java.lang.Thread	tServer

 

Constructor Summary
(package private)	ElvisComm(java.lang.String program, int port, ElvisHandler handler)           Creates a new ElvisComm, using the specified program name, port number, and handler.

 

Method Summary
void	addPropertyChangeListener(java.beans.PropertyChangeListener l)           Add a PropertyChangeListener to the listener list.
ElvisHandler	getHandler()           Return the ElvisHandler we are using.
int	getPort()           Gets the port number that we are communicating over.
ElvisCommStatus	getStatus()           Return the ElvisCommStatus corresponding to the current state of the ElvisComm.
private  void	intrusion()           This will warn the user that someone is attempting to break into his system.
(package private)  ElvisResult	perform(java.lang.String data)
(package private)  ElvisResult	perform(java.lang.String data, int timeout)           Contact the One True Elvis and request him to perform something for us.
void	removePropertyChangeListener(java.beans.PropertyChangeListener l)           Removes a PropertyChangeListener from the listener list.
void	run()           Wait for connections from other Elvises.
void	setHandler(ElvisHandler handler)           Specify a new handler for requests submitted to this Elvis.
private  void	setStatus(ElvisCommStatus status)           Update the status.
void	start()           Start the listener.
(package private)  void	stop()           Stops the server by inerrupting the thread, killing it and then closing the server itself.

 

Methods inherited from class java.lang.Object

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

 

Field Detail

port

private int port

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auth

private java.io.File auth

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key

private java.lang.String key

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tServer

private java.lang.Thread tServer

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server

private java.net.ServerSocket server

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SETTINGS_DIRECTORY

private static final java.lang.String SETTINGS_DIRECTORY

This is where we keep the file with the public information about Elvis. TODO: Make this more portable.

See Also:

Constant Field Values

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MIN_SERVER_PORT

public static final int MIN_SERVER_PORT

This value is chosen to prevent collisions with the so called "well known" ports like ftp, telnet, etc. An exception will be thrown if you try to create an ElvisComm with a port less than this value.

See Also:

Constant Field Values

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MAX_PORT_OFFSET

public static final int MAX_PORT_OFFSET

A random number between this 0 and this value will be added to the port number submitted by the user. Offsetting the port in this way decreases Elvis vulnerability to sniffing and spoofing. This should not be construed as an ironclad security mechanism - it simply makes life harder for determined attackers, and may discourage more casual attempts. If your application requires serious security, you should use a secure encryption strategy.

See Also:

Constant Field Values

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MAX_SERVER_PORT

public static final int MAX_SERVER_PORT

The maximum possible port number is 65535. Since we randomly offset from the user supplied port number we must make sure we don't exceed 65535 - thus the maximum permitted port is equal to 65535 minus the maximum offset.

See Also:

Constant Field Values

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handler

private ElvisHandler handler

This is the Elvis handler provided by the client.

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theActualPort

private int theActualPort

This is the actual port value we are listening to.

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program

private java.lang.String program

This is the name of the program, as supplied by the user. TODO: Handle multiple instances of a single Elvis program in a single JVM gracefully.

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status

private ElvisCommStatus status

This is the status of the Listener. TODO: Handle this in a more robust and coherent manner.

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propertyChangeSupport

private java.beans.PropertyChangeSupport propertyChangeSupport

Utility field used by bound properties.

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STATUS_PROPERTY

public static final java.lang.String STATUS_PROPERTY

See Also:

Constant Field Values

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emf

private ElvisMessageFactory emf

This guy puts together messages for us to send to another Elvis, either requests to be sent to the One True Elvis, or responses to be sent back to a client.

Constructor Detail

ElvisComm

ElvisComm(java.lang.String program,
          int port,
          ElvisHandler handler)

Creates a new ElvisComm, using the specified program name, port number, and handler.

Note that this does not actually initiate the listening process. You must call start() to do that.

For security reasons, the provided port is not used unmodified. Instead, a random number between 0 and MAX_PORT_OFFSET is added to it. The purpose of this is to help prevent attacks against an Elvis client operating on a known port number - if the port moves around, it makes it that much harder to establish contact.

Method Detail

start

public void start()

Start the listener.

If the process fails, an appropriate exception will be thrown, and the status will be set to ElvisCommStatus.FAILED. If we succeed, status will be set to ElvisCommStatus.OK (if we are the One True Elvis) or ElvisCommStatus.NOT_THE_KING if we are an impersonator.

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stop

void stop()

Stops the server by inerrupting the thread, killing it and then closing the server itself. Finally, it erases the authorization key.

Note: this could leave other Elvis's in the lurch. On the other hand, it is not intended that Elvis clients should persist for very long. See the Elvis documentation for more information.

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run

public void run()

Wait for connections from other Elvises. If a connection is made and accepted, we expect the other party to send us a single line, which ought to be the text form of an ElvisMessage. We reject contacts under the following circumstances:

• the connection does not originate on this host;
• the message does not parse according to the ElvisMessage rules;
• the message does not have the correct program name;
• the message does not have the correct program key.

Specified by:

run in interface java.lang.Runnable

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intrusion

private void intrusion()

This will warn the user that someone is attempting to break into his system.

TODO: Eliminate the JOptionPane - swinger though Elvis may have been, he doesn't need to be dependent on Swing.

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getHandler

public ElvisHandler getHandler()

Return the ElvisHandler we are using.

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setHandler

public void setHandler(ElvisHandler handler)

Specify a new handler for requests submitted to this Elvis. This is only valid if we are the One True Elvis, or have not yet attempted a connection.

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addPropertyChangeListener

public void addPropertyChangeListener(java.beans.PropertyChangeListener l)

Add a PropertyChangeListener to the listener list.

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removePropertyChangeListener

public void removePropertyChangeListener(java.beans.PropertyChangeListener l)

Removes a PropertyChangeListener from the listener list.

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getStatus

public ElvisCommStatus getStatus()

Return the ElvisCommStatus corresponding to the current state of the ElvisComm. Normally this will be a pretty boring item, but it can be used to track the state of the ElvisComm while it is connecting or performing a request.

Interested parties can track the status by listening on the STATUS_PROPERTY property.

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setStatus

private void setStatus(ElvisCommStatus status)

Update the status. Listeners will be notified if this is different than the previous status.

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perform

ElvisResult perform(java.lang.String data)

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perform

ElvisResult perform(java.lang.String data,
                    int timeout)

Contact the One True Elvis and request him to perform something for us.

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getPort

public int getPort()

Gets the port number that we are communicating over. This may or may not be the same as the port value originally submitted, since we use a random offset to establish the actual port number.

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Overview  Package   Class  Use  Deprecated  Index
Home >> All >> com >> synaptics >> [ elvis overview ]	PREV CLASS  NEXT CLASS
SUMMARY:  JAVADOC |  SOURCE |  DOWNLOAD | NESTED | FIELD | CONSTR | METHOD	DETAIL: FIELD | CONSTR | METHOD

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