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177 lines
5.1 KiB
Java

// STACKNetwork.java
package protocol; // protocol package
import java.util.*; // import Java utility classes
import support.*; // import Jasper support classes
/**
This is the class that supports the transport layer of a protocol stack.
@author Kenneth J. Turner
@version 1.0 (20th July 2010, KJT): initial version
*/
public class STACKNetwork implements ProtocolEntity {
/** Service message prefix */
private final static String PREFIX = "N";
/** Service receive offer */
private final static String RECEIVE =
"Send network message to transport layer";
/** Service send offer */
private final static String SEND =
"Send network message to data link layer";
/** Service message count */
private int messageCount;
/** Service provider events */
private Vector<ProtocolEvent> serviceEvents;
/** Service data unit input */
private PDU serviceIn;
/** Service data unit output */
private PDU serviceOut;
/** Service entity name */
private String serviceName;
/** Service provider */
private ProtocolEntity serviceProvider;
/** Service user */
private ProtocolEntity serviceUser;
/**
Constructor for sources/sinks.
@param serviceName service name
*/
public STACKNetwork(String serviceName) {
this.serviceName = serviceName; // set service name
initialise(); // initialise service entity
}
/**
Return the service name.
@return service name
*/
public String getName() {
return(serviceName); // return service name
}
/**
Initialise the service entity.
*/
public void initialise() {
messageCount = 0; // initialise message count
serviceEvents = new Vector<ProtocolEvent>();// initialise service events
serviceIn = null; // initialise SDU input
serviceOut = null; // initialise SDU output
}
/**
Return services currently offered.
@return list of services
*/
public Vector<String> getServices() {
Vector<String> list = new Vector<String>(); // initialise service list
if (serviceOut != null) // SDU from service user?
list.addElement(SEND); // add send SDU service to list
else if (serviceIn != null) // SDU from service provider?
list.addElement(RECEIVE); // add send SDU service to list
return(list); // return service list
}
/**
Perform service.
@param service service request
@return resulting service events
*/
public Vector<ProtocolEvent> performService(String service) {
serviceEvents = new Vector<ProtocolEvent>();// initialise service events
if (service.equals(SEND)) { // send request?
String message = // create service message
PREFIX + messageCount + ":" + serviceOut.getSDU();
PDU sdu = new STACKSdu(message); // create SDU
serviceEvents.addElement( // add send event
new ProtocolEvent(ProtocolEvent.SEND, sdu));
transmitPDU(sdu, serviceProvider); // send service message
messageCount++; // increment message count
serviceOut = null; // re-initialise SDU out
}
else if (service.equals(RECEIVE)) { // receive request?
String message = serviceIn.getSDU(); // get SDU data
int colon = message.indexOf(':'); // get first colon location
if (colon >= 0) // colon present?
message = message.substring(colon + 1); // remove prefix
serviceIn = new STACKSdu(message); // create new message
transmitPDU(serviceIn, serviceUser); // send service message
serviceEvents.addElement( // add receive event
new ProtocolEvent(ProtocolEvent.SEND, serviceIn));
serviceIn = null; // re-initialise SDU in
}
return(serviceEvents); // return service events
}
/**
Receive an SDU.
@param sdu SDU
@return resulting service events
*/
public Vector<ProtocolEvent> receivePDU(PDU sdu) {
serviceEvents = new Vector<ProtocolEvent>();// initialise service events
if (sdu != null) { // non-empty SDU?
ProtocolEntity sduSource = sdu.source; // get SDU source
String sduType = sdu.type; // get SDU type
if (sduSource.equals(serviceUser)) { // service user message?
serviceOut = sdu; // store SDU from service user
}
else if (sduSource.equals(serviceProvider)) // service provider message?
serviceIn = sdu; // store SDU from provider
}
return(serviceEvents); // return service events
}
/**
Set the service provider.
@param serviceProvider service provider
*/
public void setProvider(ProtocolEntity serviceProvider) {
this.serviceProvider = serviceProvider; // set service provider
}
/**
Set the service user.
@param serviceUser service user
*/
public void setUser(ProtocolEntity serviceUser) {
this.serviceUser = serviceUser; // set service user
}
/**
Send an SDU.
@param sdu SDU
@param dest destination protocol entity
*/
public void transmitPDU(PDU sdu, ProtocolEntity destination) {
sdu.setSource(this); // set source as this entity
sdu.setDestination(destination); // set destination
Vector<ProtocolEvent> receiveEvents = // receive SDU at destination
destination.receivePDU(sdu);
}
}