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Class simu.scp.SCP

java.lang.Object
   |
   +----java.awt.Component
           |
           +----java.awt.Container
                   |
                   +----java.awt.Panel
                           |
                           +----java.applet.Applet
                                   |
                                   +----simu.scp.SCP

public class SCP

extends Applet

Version:

1.0 1-Mar-97

Author:

Andre Campeau

The SCP (Simulator Control Program) class is used to control the simulated network environment. The simulated network environment is composed of a number of simulated network elements (SNEs), which simulate the behaviour of real hardware devices such as printers, routers or networked workstations, and house the mobile code infrastructure. Mobile code will migrate to and perform tasks in SNEs just as they would on a real network.

The SCP is a basic extension of the java.applet.Applet class.

The SCP is responsible for creating, linking, destroying, shipping code to and modifying data within these SNEs. Multiple SNEs can be created on a single workstation, or on many workstations. Currently a user must run the SNE manually on a workstation and then manually register it with the SCP.

In the future, an anchor daemon could be responsible for creating the SNE at a request from the SCP, after which the SCP would manage the SNE directly. The anchor daemon would be a Java program running on another computer which would respond to create and destroy requests from the SCP.

SNEs can be linked together, thus simulating real network connections. The SCP is responsible for managing the links between SNEs.

The SCP contains an interface component, which accepts input from a user and displays simulation data. It also contains data elements, such as global simulator data.

The user interface functions that are required for the SCP are:

• create SNEs
• manage SNE links
• destroy SNEs
• modify SNE data

The SCP uses something called a SNED, which stands for Simulated Network Element Database, to store global non-remote data, which consists of SNE registration information (IP, port, etc.) and simulated link information. For more information about the SNED, refer to the file sned.java, which contains the sned class used to implement the SNED.

SCP()

buttonCreate_Clicked(Event)

The buttonCreate_Clicked method is called when the Create button is clicked, checks that the SNEID, RealIP and RealPort fields contain data, then proceeds to enter the data into the SNE Database.

buttonDelete_Clicked(Event)

The buttonDelete_Clicked method is called when the Delete button has been clicked.

buttonDestroy_Clicked(Event)

The buttonDestroy_Clicked method is called when the Destroy button has been clicked.

buttonGetAttributes_Clicked(Event, String)

The buttonGetAttributes_Clicked method is called when the GetAttributes button has been clicked, or another method calls it explicitly.

buttonLink_Clicked(Event)

The buttonLink_Clicked method is called when the Link button has been clicked.

buttonSetLocal_Clicked(Event)

The buttonSetLocal_Clicked method is called when the Set Local button has been clicked.

buttonSetRemote_Clicked(Event)

The buttonSetRemote_Clicked method is called when the Set Remote button has been clicked.

DeleteRemoteSNEAttributes(String, int, String)

The DeleteRemoteSNEAttributes method deletes remote attributes from a remote object.

displayError(String)

The displayError method displays an error message in the Status Messages text area.

displayStatusMessage(String)

This displayStatusMessage method displays a message in the Status Messages text area, followed by a linefeed.

displayStatusMessage(String, String)

This displayStatusMessage method displays a message in the Status Messages text area, followed by a special string.

GetRemoteSNEAttributes(String, int)

The GetRemoteSNEAttributes method gets remote attributes from a remote object.

GetSNEidFromSNEAttrList()

The GetSNEidFromSNEAttrList method gets the SNEid from the first entry in the list_SNEAttributes list.

handleEvent(Event)

The handleEvent method handles events.

init()

The init method initializes and draws all applet controls in the applet window.

listSNE_Clicked(Event)

The listSNE_Clicked method responds to a double- click ACTION_EVENT by de-selecting all of the items in the list except the item that was double-clicked, then displaying the attributes for that item.

listSNEAttributes_ListSelect(Event)

The listSNEAttributes_ListSelect method is called when the list_SNEAttributes list has been selected.

SetRemoteSNEAttributes(String, int, String, String)

The SetRemoteSNEAttributes method sets remote attributes on a remote object.

  public SCP()

  public synchronized void displayStatusMessage(String Message)

This displayStatusMessage method displays a message in the Status Messages text area, followed by a linefeed.

Parameters:

message - The message to be displayed in the Status Messages text area.

  public synchronized void displayStatusMessage(String Message,
                                                String Special)

This displayStatusMessage method displays a message in the Status Messages text area, followed by a special string.

Parameters:

message - The message to be displayed in the Status Messages text area.

special - The special string to be output to the Status Messages text area. For example, if no linefeed is desired after message, special would be null.

  public synchronized void displayError(String ErrorMsg)

The displayError method displays an error message in the Status Messages text area. The Bell sound is played to indicate an error has occurred.

Parameters:

ErrorMsg - The error message to be displayed in the Status Messages text area.

  public String GetSNEidFromSNEAttrList()

The GetSNEidFromSNEAttrList method gets the SNEid from the first entry in the list_SNEAttributes list. If the text on the first line that is printed to the list by the buttonGetAttributes_Clicked method is changed, this method will have to be updated. If the list is empty, null is returned, otherwise the SNEid string is returned.

  public void GetRemoteSNEAttributes(String realIP,
                                     int realPort)

The GetRemoteSNEAttributes method gets remote attributes from a remote object. In the context of the simulated environment, this remote object will usually be a SNE, although it could be another object that supports the SNE communication protocol.

Parameters:

realIP - The IP address of the remote object.

realPort - The port that the remote object is listening on.

  public boolean SetRemoteSNEAttributes(String realIP,
                                        int realPort,
                                        String key,
                                        String value)

The SetRemoteSNEAttributes method sets remote attributes on a remote object. In the context of the simulated environment, this remote object will usually be a SNE, although it could be another object that supports the SNE communication protocol.

Parameters:

realIP - The IP address of the remote object.

realPort - The port that the remote object is listening on.

key - The key to set in the remote object's table.

value - The value corresponding to the key.

  public boolean DeleteRemoteSNEAttributes(String realIP,
                                           int realPort,
                                           String key)

The DeleteRemoteSNEAttributes method deletes remote attributes from a remote object. In the context of the simulated environment, this remote object will usually be a SNE, although it could be another object that supports the SNE communication protocol.

Parameters:

realIP - The IP address of the remote object.

realPort - The port that the remote object is listening on.

key - The key to delete in the remote object's table.

  public void buttonCreate_Clicked(Event event)

The buttonCreate_Clicked method is called when the Create button is clicked, checks that the SNEID, RealIP and RealPort fields contain data, then proceeds to enter the data into the SNE Database. (SNED)

Note that the contents of the fields are not checked, so no error is indicated for invalid IP addresses or port numbers below 1024. Also, no error is indicated when real IP + port duplicates exist in the SNED. An error is indicated when the SNE already exists in the SNED.

Parameters:

event - The Event object containing information about the event that has occurred.

  public void buttonLink_Clicked(Event event)

The buttonLink_Clicked method is called when the Link button has been clicked. It gets the SNEid's from the list_SNE list, and calls the CreateLink method in the sned class to create the link in the SNED. Note that this is all that has to be done to set up a link; remote objects like the SNE may periodically "call-in" to query the link status from the SNED. By default, the initial link status is "UP".

If two items in the SNE List are not selected, an error message is printed.

Parameters:

event - The Event object containing information about the event that has occurred.

  public void buttonDestroy_Clicked(Event event)

The buttonDestroy_Clicked method is called when the Destroy button has been clicked. It deletes all of the corresponding SNE's from the SNED and removes their list entries from the list_SNE list.

If no items are selected, an error message is printed.

Parameters:

event - The Event object containing information about the event that has occurred.

  public void buttonGetAttributes_Clicked(Event event,
                                          String SNEid)

The buttonGetAttributes_Clicked method is called when the GetAttributes button has been clicked, or another method calls it explicitly. It gets both the local attributes from the SNED and the remote attributes from the SNE in another JVM, and displays these attributes in the Attributes list.

Note that this method performs two functions, depending upon parameters that are supplied to it by callers.

1. Obtain all attributes, including both local and remote attributes, and display them in the Attributes list (list_SNEAttributes).
2. Obtain only local attributes, use the remote attributes from a previous call, and display them in the Attributes list (list_SNEAttributes).

Function (1) is selected when the user explicitly hits the Get Attributes button or double-clicks on an entry in the list_SNE list. Function (2) is selected when a method has changed attributes only in the local SNED, and wishes to show the user these attributes immediately after the change (i.e. when a link is deleted). The reason for function (2) is that local updates may happen often, and to have the entire attribute list sent from a remote object each time would be costly in terms of network bandwidth.

If no items are selected, an error message is printed.

Parameters:

event - The Event object containing information about the event that has occurred.

SNEid - The SNEid which is not null if function (2) is required.

  public void listSNE_Clicked(Event event)

The listSNE_Clicked method responds to a double- click ACTION_EVENT by de-selecting all of the items in the list except the item that was double-clicked, then displaying the attributes for that item.

Parameters:

event - The Event object containing information about the event that has occurred.

  public void buttonSetRemote_Clicked(Event event)

The buttonSetRemote_Clicked method is called when the Set Remote button has been clicked. It gets the text from the Key and Value text fields, and updates a remote database with these new values by calling the SetRemoteSNEAttributes method. Note that the Attributes list is cleared immediately after this method executes, which will force the user to manually re-display the remote attributes. This is an extra confirmation step that will ensure that the attribute was successfully transported to its remote destination.

If the Key text field is empty, an error message is displayed.

Parameters:

event - The Event object containing information about the event that has occurred.

  public void buttonSetLocal_Clicked(Event event)

The buttonSetLocal_Clicked method is called when the Set Local button has been clicked. It gets the text from the Key and Value text fields, and updates the SNED with these new values by calling the appropriate method. Note that the Attributes list is updated immediately after this command executes.

There are two areas in the Attributes list that are affected by a Set Local button click: the Local and Links areas. Some calculations are done to determine which area the selection falls under, then appropriate action is taken.

Parameters:

event - The Event object containing information about the event that has occurred.

  public void buttonDelete_Clicked(Event event)

The buttonDelete_Clicked method is called when the Delete button has been clicked. It gets the SNEid from the Attributes list, gets the key from the Key text field, and calls the appropriate method to delete the item from the database.

There are two areas in the Attributes list that are affected by a Delete button click: the Links and Remote areas. Some calculations are done to determine which area the selection falls under, then appropriate action is taken.

Parameters:

event - The Event object containing information about the event that has occurred.

  public void listSNEAttributes_ListSelect(Event event)

The listSNEAttributes_ListSelect method is called when the list_SNEAttributes list has been selected. This means that the user has clicked on an item in the Attributes list. There are many possible actions for this event.

The sole purpose of this method is to enable and/or disable one or more of the Set Remote, Set Local, and Delete buttons, and the Key and Value text fields. Also, the Key and Value text fields are set to the key and value as selected from the list, as appropriate.

An important point to note is that if no item in the Attribute list is selected, all of the aforementioned objects are disabled. In order to enable selected objects, the user must click on an attribute in one of the three areas (Local, Links and Remote). In the case where there are no entries in the Remote area, the user should click on the area title in order to enable Key & Value text fields (as well as the Set Remote and Delete buttons). This will allow the user to set new attributes on remote objects.

Parameters:

event - The Event object containing information about the event that has occurred.

  public void init()

The init method initializes and draws all applet controls in the applet window.

This method is automatically created and updated by Visual Cafe.

Overrides:

init in class Applet

  public boolean handleEvent(Event event)

The handleEvent method handles events. When an event occurs, the handleEvent method is called, and depending upon the object and type of event, a specific event handler method is then called.

This method is automatically created and updated by Visual Cafe.

Parameters:

event - The Event object containing information about the event that has occurred.

Overrides:

handleEvent in class Component

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