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Cristal-ise is a description-driven software platform originally developed to track the construction of the CMS ECAL detector of the LHC at CERN. This is its core library, known as the kernel, which manages business objects called Items. Items are entirely configured from data, called descriptions, held in other Items. Every change of a state in an Item is a consequence of an execution of an activity in that Item's lifecycle, meaning that Cristal-ise applications are completely traceable, even in their design. It also supports extensive versioning of Item description data, giving the system a high level of flexibility.

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/**
 * This file is part of the CRISTAL-iSE kernel.
 * Copyright (c) 2001-2015 The CRISTAL Consortium. All rights reserved.
 *
 * This library is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as published
 * by the Free Software Foundation; either version 3 of the License, or (at
 * your option) any later version.
 *
 * This library is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; with out even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
 * License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this library; if not, write to the Free Software Foundation,
 * Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
 *
 * http://www.fsf.org/licensing/licenses/lgpl.html
 */
package org.cristalise.kernel.utils.server;

import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;
import java.net.SocketException;
import java.net.SocketTimeoutException;
import java.util.ArrayList;
import java.util.ListIterator;
import java.util.NoSuchElementException;

import org.cristalise.kernel.utils.Logger;



public class SimpleTCPIPServer implements Runnable {

    int                      port            = 0;
    int                      maxConn         = 10;
    Thread                   listener        = null;
    Class                 handlerClass    = null;
    ServerSocket             serverSocket    = null;
    boolean                  keepListening   = true;
    ArrayList currentHandlers = new ArrayList();
    static short             numberOfServers = 0;

    public SimpleTCPIPServer(int port, Class handlerClass, int maxConnections) {
        this.port         = port;
        this.handlerClass = handlerClass;
        this.maxConn      = maxConnections;
        numberOfServers++;
    }

    public void startListening() {
        if(listener != null) return;
        keepListening = true;

        listener = new Thread(this);
        listener.start();
    }

    public void stopListening() {
        Logger.msg("SimpleTCPIPServer.stopListening() - Closing server for " + handlerClass.getName() +" on port "+ port);

        keepListening = false;
        for (SocketHandler thisHandler : currentHandlers) {
            thisHandler.shutdown();
        }
        try {
            if (serverSocket!=null) serverSocket.close();
        }
        catch (IOException e) { }
    }

    @Override
	public void run() {
        Thread.currentThread().setName("TCP/IP Server for class "+handlerClass.getName());
        Socket connectionSocket = null;

        try {
            serverSocket = new ServerSocket(port);
            if (port == 0) port = serverSocket.getLocalPort();

            Logger.msg("SimpleTCPIPServer.run() - Created server for " + handlerClass.getName()+" on port "+port);

            serverSocket.setSoTimeout(500);
            SocketHandler freeHandler = null;

            while(keepListening) {
                if (freeHandler == null || freeHandler.isBusy()) {
                    ListIterator i = currentHandlers.listIterator();
                    try {
                        do {
                            freeHandler = i.next();
                        }
                        while (freeHandler.isBusy());
                    }
                    catch (NoSuchElementException e) {
                        // create new one
                        if (currentHandlers.size() < maxConn) {
                            freeHandler = (SocketHandler)handlerClass.newInstance();
                            currentHandlers.add(freeHandler);
                        }
                        else { // max handlers are created. wait for a while, then look again
                            Logger.warning("No free handlers left for "+handlerClass.getName()+" on port "+ port + "! Sleeping 2s.");
                            Thread.sleep(2000);
                            continue;
                        }
                    }
                }

                try {
                    connectionSocket = serverSocket.accept();
                    if (keepListening) {
                        Logger.msg("SimpleTCPIPServer: Connection to "+freeHandler.getName()+" from "+ connectionSocket.getInetAddress());

                        freeHandler.setSocket(connectionSocket);
                        new Thread(freeHandler).start();
                    }
                } 
                catch (SocketTimeoutException ex1) { }// timeout just to check if we've been told to die
                catch (SocketException ex1)        { } // we were closed during shutdown
            }
            serverSocket.close();
            Logger.msg("SimpleTCPIPServer: Server closed for " + handlerClass.getName() +" on port "+ port);
        }
        catch(Exception ex) {
            Logger.error("SimpleTCPIPServer.run(): Fatal Error. Listener for '"+handlerClass.getName()+"' will stop.");
            Logger.error(ex);
        }
        listener = null;
        Logger.msg("SimpleTCPIPServer - Servers still running: "+--numberOfServers);
    }

    public int getPort() {
        return port;
    }
}