InterfaceServer.java:

/*

Communication Interface for Virtual Classroom Components.
Complied in JDK 1.4.2
Usage:

Step1: Create your component which implemnts Interface
ComponentBase.

Step2: Replace the ComponentMy with your class name in
InterfaceServer::main().

Step3: start up Interface Server by
java InterfaceServer

Step4: Use Virtual remote which is also provided on the
web to send message and get the feedback message.

*/


import java.io.*;
import java.net.*;
import java.util.*;

/*
Class KeyValueList:
List of (Key, Value) pair--the basic format of message
Keys: MsgID and Description are required for any messages
MsgID 0-999 is reserved for system use.
You MsgID could start from 1000.
*/

class KeyValueList{
private Vector Keys;
private Vector Values;

/* Constructor */
public KeyValueList(){
Keys=new Vector();
Values=new Vector();
}

/* Look up the value given key, used in getValue() */

private int lookupKey(String strKey){
for(int i=0;i<Keys.size();i++){
String k=(String) Keys.elementAt(i);
if (strKey.equals(k)) return i;
}
return -1;
}

/* add new (key,value) pair to list */

public boolean addPair(String strKey,String strValue){
return (Keys.add(strKey)&& Values.add(strValue));
}

/* get the value given key */

public String getValue(String strKey){
int index=lookupKey(strKey);
if (index==-1) return null;
return (String) Values.elementAt(index);
}

/* Show whole list */
public String toString(){
String result = new String();
for(int i=0;i<Keys.size();i++){
result+=(String) Keys.elementAt(i)+":"+(String) Values.elementAt(i)+"\n";
}
return result;
}

public int size(){ return Keys.size(); }

/* get Key or Value by index */
public String keyAt(int index){ return (String) Keys.elementAt(index);}
public String valueAt(int index){ return (String) Values.elementAt(index);}
}

/*
Class MsgEncoder:
Serialize the KeyValue List and Send it out to a Stream.
*/
class MsgEncoder{
private PrintStream printOut;
/* Default of delimiter in system is $$$ */
private final String delimiter="$$$";

public MsgEncoder(){
}

/* Encode the Key Value List into a string and Send it out */

public void sendMsg(KeyValueList kvList, OutputStream out) throws IOException{
PrintStream printOut= new PrintStream(out);
if (kvList==null) return;
String outMsg= new String();
for(int i=0; i<kvList.size();i++){
if (outMsg.equals(""))
outMsg=kvList.keyAt(i)+delimiter + kvList.valueAt(i);
else
outMsg+=delimiter+kvList.keyAt(i)+delimiter + kvList.valueAt(i);
}
//System.out.println(outMsg);
printOut.println(outMsg);
}
}

/*
Class MsgDecoder:
Get String from input Stream and reconstruct it to
a Key Value List.
*/

class MsgDecoder {

private BufferedReader bufferIn;
private final String delimiter="$$$";

public MsgDecoder(InputStream in){
bufferIn = new BufferedReader(new InputStreamReader(in));
}

/*
get String and output KeyValueList
*/

public KeyValueList getMsg() throws IOException{
String strMsg= bufferIn.readLine();

if (strMsg==null) return null;

KeyValueList kvList = new KeyValueList();
StringTokenizer st = new StringTokenizer(strMsg,delimiter);
while (st.hasMoreTokens()) {
kvList.addPair(st.nextToken(),st.nextToken());
}
return kvList;
}

}

/*
interface ComponentBase:
The interface you have to implement in your component
*/
interface ComponentBase{
   public KeyValueList processMsg(KeyValueList kvList);
}

/*
Class InterfaceServer
Set up a socket server waiting for the remote to connect.
*/

public class InterfaceServer
{

   public static final int port=7999;

   public static void main(String[] args) throws Exception
  {
     ServerSocket server = new ServerSocket(port);

    /*
    You need to create your component here
    */

    ComponentBase compMy= new componentMy();
    Socket client = server.accept();
    try{
      MsgDecoder mDecoder= new MsgDecoder(client.getInputStream());
      MsgEncoder mEncoder= new MsgEncoder();
      KeyValueList kvInput,kvOutput;
      do
      {
        kvInput=mDecoder.getMsg();
        if (kvInput!=null) {
        System.out.println("Incomming Message:\n");
        System.out.println(kvInput);
        KeyValueList kvResult=compMy.processMsg(kvInput);
        System.out.println("Outgoing Message:\n");
        System.out.println(kvResult);
        mEncoder.sendMsg(kvResult,client.getOutputStream());
       }
      }
      while (kvInput!=null);
   }
   catch (SocketException e){
   System.out.println("Connection was Closed by Client");
  }
 }
}