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387 lines
12 KiB
Java
387 lines
12 KiB
Java
// ABRAProtocol.java
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package protocol;
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import java.util.*;
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import support.*;
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/**
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This is the class for the Abracadabra protocol sender.
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@author Iain A. Robin, Kenneth J. Turner
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@version 1.0 (1st September 1999, IAR): initial version
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<br/> 1.4 (9th March 2006, KJT): updated for JDK 1.5
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<br/> 1.5 (27th July 2010, KJT): minor tidying
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*/
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public class ABRAProtocol implements ProtocolEntity, Timeouts {
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// Protocol state constants
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private static final int CLOSED = 0; // waiting for connection request
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private static final int CR_SENT = 1; // waiting for connection confirmation
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private static final int CR_RECV = 2; // waiting for ConResp from user
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private static final int SEND = 3; // prepared to send data PDU
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private static final int WAIT = 4; // waiting for acknowledgement of data
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private static final int DR_SENT = 5; // waiting for disconnection confirm
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// Protocol data unit types
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public static final String CR = "Connection Request";
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public static final String CC = "Connection Confirmation";
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public static final String DT = "Data Transfer";
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public static final String AK = "Acknowledgement";
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public static final String DR = "Disconnection Request";
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public static final String DC = "Disconnection Confirmation";
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public static final int maxRetries = 3;
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private PDU pduSent;
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private PDU lastDTpdu;
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private int sendSeq;
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private int recvSeq;
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private ProtocolEntity peer;
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private ABRAService user;
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private Vector<ProtocolEvent> entityEvents; // events from entity
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private Medium medium;
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private String name;
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private boolean timerEnabled;
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private int crRemaining;
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private int drRemaining;
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private int dtRemaining;
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private boolean dtOrAk;
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private int state;
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public ABRAProtocol(Medium m, String name) {
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this.name = name;
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medium = m;
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initialise();
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}
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public String getName() {
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return(name);
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}
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public Vector<String> getServices() {
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Vector<String> list = new Vector<String>();
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switch (state) {
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case CR_SENT: // waiting for connection confirmation
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if (timerEnabled) {
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if (crRemaining > 1)
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list.addElement("Timeout - resend " + CR);
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else
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list.addElement("Retry limit reached - send " + DR);
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}
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break;
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case WAIT: // waiting for acknowledgement of data
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if (timerEnabled) {
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if (dtRemaining > 1)
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list.addElement("Timeout - resend DT(" + lastDTpdu.seq + ")" );
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else
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list.addElement("Retry limit reached - send " + DR);
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}
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break;
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case DR_SENT: // waiting for disconnection confirmation
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if (timerEnabled) {
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if (drRemaining > 1) {
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list.addElement("Timeout - resend " + DR);
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}
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else {
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// Retry limit reached
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dtRemaining--;
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state = CLOSED;
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}
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}
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break;
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}
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return(list);
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}
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/** Increment PDU sequence number (alternating bit) */
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private int inc(int seq) {
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return(1 - seq);
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}
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public void initialise() {
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entityEvents = new Vector<ProtocolEvent>();
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state = CLOSED;
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}
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public boolean hasTimer(String type) {
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return(type.equals("DT") || type.equals("DR") || type.equals("CR"));
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}
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public Vector<ProtocolEvent> performService(String s) {
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Vector<ProtocolEvent> events = new Vector<ProtocolEvent>();
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switch (state) {
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case CR_SENT:
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if (s.startsWith("Timeout")) {
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crRemaining--;
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transmitPDU(new PDU("CR"), peer); // resend connection request PDU
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events.addElement(
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new ProtocolEvent(ProtocolEvent.TIMEOUT, pduSent));
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}
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if (s.startsWith("Retry limit")) {
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crRemaining--;
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transmitPDU(new PDU("DisInd"), user);
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events.addElement(
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new ProtocolEvent(ProtocolEvent.DELIVER, pduSent));
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transmitPDU(new PDU("DR"), peer); // send disconnection request PDU
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events.addElement(
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new ProtocolEvent(ProtocolEvent.TRANSMIT, pduSent));
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drRemaining = maxRetries;
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state = DR_SENT;
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}
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break;
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case WAIT:
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if (s.startsWith("Timeout")) {
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dtRemaining--;
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transmitPDU(lastDTpdu, peer);
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events.addElement(
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new ProtocolEvent(ProtocolEvent.TIMEOUT, pduSent));
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}
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if (s.startsWith("Retry limit")) {
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transmitPDU(new PDU("DisInd"), user);
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events.addElement(
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new ProtocolEvent(ProtocolEvent.TRANSMIT, pduSent));
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dtRemaining--;
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transmitPDU(new PDU("DR"), peer); // send disconnection request PDU
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events.addElement(
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new ProtocolEvent(ProtocolEvent.TRANSMIT, pduSent));
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drRemaining = maxRetries;
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state = DR_SENT;
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}
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break;
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case DR_SENT:
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if (s.startsWith("Timeout")) {
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drRemaining--;
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transmitPDU(new PDU("DR"), peer);
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events.addElement(
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new ProtocolEvent(ProtocolEvent.TIMEOUT, pduSent));
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}
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break;
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}
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for (Enumeration e = entityEvents.elements(); e.hasMoreElements(); )
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events.addElement((ProtocolEvent) e.nextElement());
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return(events);
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}
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public Vector<ProtocolEvent> receivePDU(PDU pdu) {
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Vector<ProtocolEvent> events = new Vector<ProtocolEvent>();
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String pduType = "";
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if (pdu != null)
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pduType = pdu.type;
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switch (state) {
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case CLOSED:
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if (pduType.equals("ConReq")) { // ConReq primitive?
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transmitPDU(new PDU("CR"), peer); // send connection request PDU
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dtOrAk = false;
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sendSeq = 0;
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recvSeq = 0;
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crRemaining = maxRetries;
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state = CR_SENT;
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events.addElement(new ProtocolEvent(ProtocolEvent.TRANSMIT, pduSent));
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}
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else if (pduType.equals("CR")) { // connection request PDU?
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transmitPDU(new PDU("ConInd"), user);
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events.addElement(new ProtocolEvent(ProtocolEvent.DELIVER, pduSent));
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dtOrAk = false;
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sendSeq = 0;
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recvSeq = 0;
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state = CR_RECV;
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}
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else if (pduType.equals("DR")) { // got disconnect request PDU
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transmitPDU(new PDU("DC"), peer); // send disconnect confirm PDU
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events.addElement(new ProtocolEvent(ProtocolEvent.TRANSMIT, pduSent));
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}
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break;
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case CR_SENT:
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if (pduType.equals("CC") || // connection confirmation PDU?
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pduType.equals("CR")) { // connection request PDU?
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// (both stations have requested connections at the same time)
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transmitPDU(new PDU("ConConf"), user);
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events.addElement(new ProtocolEvent(ProtocolEvent.DELIVER, pduSent));
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timerEnabled = false;
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state = SEND;
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}
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else if (pduType.equals("DR")) { // disconnection request PDU?
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transmitPDU(new PDU("DisInd"), user);
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events.addElement(new ProtocolEvent(ProtocolEvent.DELIVER, pduSent));
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timerEnabled = false;
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state = CLOSED;
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}
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else if (pduType.equals("DisReq")) { // disconnection request prim?
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// transmitPDU(new PDU("DisInd"), user);
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// events.addElement(
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// new ProtocolEvent(ProtocolEvent.DELIVER, pduSent));
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transmitPDU(new PDU("DR"), peer); // send disconnect request PDU
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events.addElement(new ProtocolEvent(ProtocolEvent.TRANSMIT, pduSent));
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drRemaining = maxRetries;
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state = DR_SENT;
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}
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break;
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case CR_RECV:
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if (pduType.equals("ConResp")) {
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transmitPDU(new PDU("CC"), peer); // send connection confirm PDU
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events.addElement(new ProtocolEvent(ProtocolEvent.TRANSMIT, pduSent));
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state = SEND;
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}
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else if (pduType.equals("DR")) {
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transmitPDU(new PDU("DisInd"), user);
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events.addElement(
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new ProtocolEvent(ProtocolEvent.DELIVER, pduSent));
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transmitPDU(new PDU("DC"), peer); // send disconnection confirm PDU
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events.addElement(new ProtocolEvent(ProtocolEvent.TRANSMIT, pduSent));
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state = CLOSED;
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}
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else if (pduType.equals("ConReq")) {
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transmitPDU(new PDU("ConConf"), user);
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events.addElement(
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new ProtocolEvent(ProtocolEvent.DELIVER, pduSent));
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transmitPDU(new PDU("CC"), peer); // send connection confirm PDU
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events.addElement(new ProtocolEvent(ProtocolEvent.TRANSMIT, pduSent));
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state = SEND;
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}
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else if (pduType.equals("DisReq")) {
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transmitPDU(new PDU("DR"), peer); // send disconnect request PDU
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events.addElement(new ProtocolEvent(ProtocolEvent.TRANSMIT, pduSent));
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state = CLOSED;
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}
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break;
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case WAIT:
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if (pduType.equals("AK")) {
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if (pdu.seq == sendSeq) {
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dtOrAk = true;
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timerEnabled = false;
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user.setOKToSend(true);
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state = SEND;
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}
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else { // wrong AK : enter error phase
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transmitPDU(new PDU("DisInd"), user);
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events.addElement(
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new ProtocolEvent(ProtocolEvent.DELIVER, pduSent));
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transmitPDU(new PDU("DR"), peer); // send disconnect request PDU
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events.addElement(
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new ProtocolEvent(ProtocolEvent.TRANSMIT, pduSent));
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drRemaining = maxRetries;
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state = DR_SENT;
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}
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}
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// break intentionally omitted
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case SEND:
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if (state == SEND // avoid drop-through from WAIT
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&& pduType.equals("DatReq")) { // DatReq received from user
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transmitPDU(new PDU("DT", sendSeq, pdu.getSDU()), peer);
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events.addElement(
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new ProtocolEvent(ProtocolEvent.TRANSMIT, pduSent));
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user.setOKToSend(false);
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sendSeq = inc(sendSeq);
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dtRemaining = maxRetries;
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state = WAIT;
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}
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else if (pduType.equals("DR")) { // disconnection request PDU?
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transmitPDU(new PDU("DisInd"), user);
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events.addElement(
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new ProtocolEvent(ProtocolEvent.DELIVER, pduSent));
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transmitPDU(new PDU("DC"), peer);
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events.addElement(new ProtocolEvent(ProtocolEvent.TRANSMIT, pduSent));
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timerEnabled = false;
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state = CLOSED;
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}
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else if (pduType.equals("DT")) { // data PDU received
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dtOrAk = true;
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if (pdu.seq == recvSeq) { // check sequence number correct
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recvSeq = inc(recvSeq);
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transmitPDU(new PDU("DatInd", pdu.getSDU()), user);
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events.addElement(
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new ProtocolEvent(ProtocolEvent.DELIVER, pduSent));
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}
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transmitPDU(new PDU("AK", recvSeq), peer);
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events.addElement(new ProtocolEvent(ProtocolEvent.TRANSMIT, pduSent));
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// no state transition
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}
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if (pduType.equals("CC") || pduType.equals("DC")) {
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transmitPDU(new PDU("DisInd"), user);
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events.addElement(new ProtocolEvent(ProtocolEvent.DELIVER, pduSent));
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transmitPDU(new PDU("DR"), peer);
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events.addElement(new ProtocolEvent(ProtocolEvent.TRANSMIT, pduSent));
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drRemaining = maxRetries;
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state = DR_SENT;
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}
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if (pduType.equals("CR")) { // connection request PDU?
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if (!dtOrAk) {
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transmitPDU(new PDU("CC"), peer);
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events.addElement(
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new ProtocolEvent(ProtocolEvent.TRANSMIT, pduSent));
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// no state transition
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}
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else {
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transmitPDU(new PDU("DisInd"), user);
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events.addElement(
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new ProtocolEvent(ProtocolEvent.DELIVER, pduSent));
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transmitPDU(new PDU("DR"), peer);
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events.addElement(
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new ProtocolEvent(ProtocolEvent.TRANSMIT, pduSent));
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drRemaining = maxRetries;
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state = DR_SENT;
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}
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}
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if (pduType.equals("DisReq")) {
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transmitPDU(new PDU("DR"), peer);
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events.addElement(new ProtocolEvent(ProtocolEvent.TRANSMIT, pduSent));
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drRemaining = maxRetries;
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state = DR_SENT;
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}
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break;
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case DR_SENT: // awaiting disconnect confirm
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if (pduType.equals("DC") || // disconnect confirm PDU?
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pduType.equals("DR")) { // disconnect request PDU?
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// both stations have requested disconnection at the same time
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timerEnabled = false;
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state = CLOSED;
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}
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if (pduType.equals("ConReq")) {
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transmitPDU(new PDU("DisInd"), user);
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events.addElement(new ProtocolEvent(ProtocolEvent.DELIVER, pduSent));
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}
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if (timerEnabled && drRemaining <= 1) {
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drRemaining--;
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state = CLOSED;
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}
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break;
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}
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return(events);
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}
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public void setPeer(ProtocolEntity peer) {
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this.peer = peer;
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}
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/**
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Set the timer for a specified PDU.
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@param pdu PDU
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@param enabled whether the timer is enabled
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*/
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public void setTimer(PDU pdu, boolean enabled) {
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timerEnabled = enabled;
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}
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public void setUser(ProtocolEntity user) {
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this.user = (ABRAService)user;
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}
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public void transmitPDU(PDU pdu, ProtocolEntity destination) {
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pdu.setSource(this);
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pdu.setDestination(destination);
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if (destination == peer)
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entityEvents = medium.receivePDU(pdu);
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else
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entityEvents = user.receivePDU(pdu);
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pduSent = pdu;
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if (pdu.type.equals("DT"))
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lastDTpdu = pdu;
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for (Enumeration e = entityEvents.elements(); e.hasMoreElements(); )
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System.err.println("ABRAP transmitPDU: " + (ProtocolEvent) e.nextElement());
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}
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}
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