// SelectScoreServer.java// Andrew Davison, December 2002, dandrew@ratree.psu.ac.th/* 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