You cannot select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
126 lines
3.8 KiB
Java
126 lines
3.8 KiB
Java
// TCPMedium.java
|
|
|
|
package protocol; // protocol package
|
|
|
|
import java.util.*; // import Java utility classes
|
|
|
|
import support.*; // import Jasper support classes
|
|
|
|
/**
|
|
This is the class for a TCP medium.
|
|
|
|
@author Iain A. Robin, Kenneth J. Turner
|
|
@version 1.0 (1st September 1999, IAR): initial version
|
|
<br/> 1.4 (9th March 2006, KJT): updated for JDK 1.5
|
|
<br/> 1.5 (26th July 2010, KJT): minor tidying; a loss rate has been
|
|
introduced for medium messages
|
|
*/
|
|
public class TCPMedium extends Medium {
|
|
|
|
/** Message loss rate (0.2 means 20% of messages are lost) */
|
|
private float lossRate = 0.2f;
|
|
|
|
/** Random number index */
|
|
private int randomIndex;
|
|
|
|
/** Random numbers */
|
|
private Vector<Float> randomNumbers;
|
|
|
|
/**
|
|
Constructor for a TCP medium.
|
|
*/
|
|
public TCPMedium() {
|
|
super(); // construct superclass
|
|
randomNumbers = new Vector<Float>(); // initialise random numbers
|
|
}
|
|
|
|
/**
|
|
Initialise the medium.
|
|
*/
|
|
public void initialise() {
|
|
super.initialise();
|
|
randomIndex = 0; // initialise random index
|
|
}
|
|
|
|
/**
|
|
Gets the matching PDU.
|
|
|
|
@param description PDU description
|
|
@return matching PDU
|
|
*/
|
|
protected PDU getMatchingPDU(String description) {
|
|
// identify and return PDU currently on channel with
|
|
// type and parameters matching those described in given string
|
|
TCPMessage tcpdu;
|
|
// try to match PDU type and seq with a PDU currently on channel:
|
|
for (Enumeration enumeration = pdus.elements();
|
|
enumeration.hasMoreElements(); ) {
|
|
tcpdu = (TCPMessage) enumeration.nextElement();
|
|
if (description.indexOf(tcpdu.getID()) > 0)
|
|
return (tcpdu);
|
|
}
|
|
return (null); // no match found
|
|
}
|
|
|
|
/**
|
|
Return a list of strings describing actions (services) that can be carried
|
|
out in the current state.
|
|
|
|
@return service descriptions
|
|
*/
|
|
public Vector<String> getServices() {
|
|
Vector<String> list = new Vector<String>(); // initialise service list
|
|
HashSet<String> pdusSent = // initialise list of sources
|
|
new HashSet<String>();
|
|
for (Enumeration enumeration = pdus.elements(); // go through PDUs
|
|
enumeration.hasMoreElements(); ) {
|
|
PDU pdu = (PDU) enumeration.nextElement();// get next PDU
|
|
if (pdu != null) { // non-null PDU?
|
|
String name = pdu.getSource().getName();// get PDU source name
|
|
String description = // get PDU id and name
|
|
pdu.getID() + " [" + name + "]";
|
|
if (!pdusSent.contains(name)) { // no PDU with this source?
|
|
pdusSent.add(name); // add source to list
|
|
list.addElement( // add delivery service
|
|
"Deliver " + description + " - no loss");
|
|
}
|
|
if (random() < lossRate) // loss is possible?
|
|
list.addElement( // add loss service
|
|
"Lose " + description + " - congestion/error");
|
|
}
|
|
}
|
|
return(list); // return service list
|
|
}
|
|
|
|
/**
|
|
Return a random float. If the list of randoms contains an unused value then
|
|
use this, otherwise generate a fresh value and add to the list. This allows
|
|
random numbers to be generated consistently when simulation steps are
|
|
undone/redone.
|
|
|
|
@return random number in the range (0..1]
|
|
*/
|
|
private float random() {
|
|
if (randomIndex < randomNumbers.size()) // index within list?
|
|
return( // return this random
|
|
((Float)randomNumbers.elementAt(randomIndex++)).floatValue());
|
|
else { // index not within list
|
|
Float random = new Float(Math.random()); // get random number
|
|
randomNumbers.addElement(random); // add random to list
|
|
randomIndex++; // increment list index
|
|
return(random.floatValue()); // return rand number
|
|
}
|
|
}
|
|
|
|
/**
|
|
Set the medium loss rate.
|
|
|
|
@param lossRate loss rate
|
|
*/
|
|
public void setLossRate(float lossRate) {
|
|
this.lossRate = lossRate; // set loss rate
|
|
}
|
|
|
|
}
|
|
|