selectscoreserver.java

java3D game engine design of the source [three-dimensionalvirtualrealitynetworkprogram] - "virtual

// SelectScoreServer.java
// Andrew Davison, December 2002, [e-mail]

/* A non-blocking  sequential server that stores a client's score
   (and name) in a list of top-10 high scores.

   Understood input messages:
		get					   -- returns the high score list
        score name & score &   -- add the score for name
		bye					   -- terminates the client link

   The list is maintained in a file SCORFN, and loaded when the
   server starts.
   The server is terminated with a ctrl-C

   Derived from SelectSockets.java 

   We use non-blocking detection of new socket channel
   connections from clients _and_ use non-blocking reading
   of those channels.

*/

import java.io.*;
import java.net.*;
import java.nio.*;
import java.nio.channels.*;
// import java.nio.charset.*;
import java.util.*;


public class SelectScoreServer
{
  private static final int PORT_NUMBER = 1234;

  private HighScores hs;
  private HashMap clients;   // map of channels to ClientInfo objects


  public SelectScoreServer()
  {
    hs = new HighScores();
    clients = new HashMap();
    try {
      System.out.println("Listening on port " + PORT_NUMBER);

      // set up server channel and socket
      ServerSocketChannel serverChannel = ServerSocketChannel.open();
      serverChannel.configureBlocking (false);   // use non-blocking mode

      ServerSocket serverSocket = serverChannel.socket();
      serverSocket.bind( new InetSocketAddress(PORT_NUMBER) );    // set port for listening

      Selector selector = Selector.open();
      serverChannel.register(selector, 
						SelectionKey.OP_ACCEPT);   // register channel with selector

      while (true) {
        // System.out.println("No. of clients: " + clients.size());
        selector.select();     // wait for ready channels
        Iterator it = selector.selectedKeys().iterator();   // get iterator for keys
        SelectionKey key;
        while (it.hasNext()) {       // look at each key
          key = (SelectionKey) it.next();   // get a key
          it.remove();                      // remove it
          if (key.isAcceptable())       // a new connection?
            newChannel(key, selector);
          else if (key.isReadable())    // data to be read?
            readFromChannel(key);
          else
            System.out.println("Did not process key: " + key);
        }
      }
    }
    catch(IOException e) 
    {  System.out.println(e); }
  } // end of SelectScoreServer()


  private void newChannel(SelectionKey key, Selector selector)
  // Add the socket channel for a new client to the selector
  {
    try {
      ServerSocketChannel server = (ServerSocketChannel) key.channel();
      SocketChannel channel = server.accept();           // get the channel
      channel.configureBlocking (false);                 // use non-blocking
      channel.register(selector, SelectionKey.OP_READ);  // register it with selector

      clients.put(channel, 
				new ClientInfo(channel, this) );   // store info
    }
    catch (IOException e)
    {  System.out.println( e ); }
  }  // end of newChannel()



  private void readFromChannel(SelectionKey key)
  // process input that is waiting on a channel
  {
    SocketChannel channel = (SocketChannel) key.channel();
    ClientInfo ci = (ClientInfo) clients.get(channel);
    if (ci == null)
      System.out.println("No client info for channel " + channel);
    else {
      String msg = ci.readMessage();
      if (msg != null) {
        System.out.println("Read message: " + msg);
        if (msg.trim().equals("bye")) {
          ci.closeDown();
          clients.remove(channel);  // delete ci from hash map
        }
        else 
          doRequest(msg, ci);
      }
    }
  } // end of readFromChannel()



  private void doRequest(String line, ClientInfo ci)
  /*  The input line can be one of:
             "score name & score &"
      or     "get"
  */
  {
    if (line.trim().toLowerCase().equals("get")) {
      System.out.println("Processing 'get'");
      ci.sendMessage( hs.toString() );
    }
    else if ((line.length() >= 6) &&     // "score "
        (line.substring(0,5).toLowerCase().equals("score"))) {
      System.out.println("Processing 'score'");
      hs.addScore( line.substring(5) );    // cut the score keyword
    }
    else
      System.out.println("Ignoring input line");
  }  // end of doRequest()


  public void removeChannel(SocketChannel chan)
  // called by ClientInfo object when channel is closed
  {  clients.remove(chan);  }


  // --------------------------------------------

  public static void main(String[] argv)
  {  new SelectScoreServer();  }


} // end of SelectScoreServer class