de.ailis.oneinstance.OneInstanceServer.java Source code

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Here is the source code for de.ailis.oneinstance.OneInstanceServer.java

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/*
 * Copyright (C) 2012 Klaus Reimer <k@ailis.de>
 * See LICENSE.txt for licensing information.
 */

package de.ailis.oneinstance;

import java.io.IOException;
import java.net.InetAddress;
import java.net.ServerSocket;
import java.net.Socket;
import java.net.SocketTimeoutException;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

/**
 * The server socket which listens for new instances.
 * 
 * @author Klaus Reimer (k@ailis.de)
 */
final class OneInstanceServer implements Runnable {
    /** The logger. */
    private static final Log LOG = LogFactory.getLog(OneInstanceServer.class);

    /** The application name. */
    private String appId;

    /** The port number. */
    private int port;

    /** The server socket. */
    private ServerSocket socket;

    /** Flag indicating if thread is about to stop. */
    private boolean stop;

    /** The listen thread. */
    private Thread thread;

    /**
     * Constructor.
     * 
     * @param appId
     *            The application name.
     * @param port
     *            The application port.
     * @throws PortAlreadyInUseException
     *             When port is already in use.
     */
    OneInstanceServer(final String appId, final int port) throws PortAlreadyInUseException {
        this.appId = appId;
        this.port = port;

        try {
            this.socket = new ServerSocket(this.port, 50, InetAddress.getByName(null));
            this.socket.setSoTimeout(250);
        } catch (final IOException e) {
            throw new PortAlreadyInUseException();
        }
    }

    /**
     * Accept new client connection.
     * 
     * @return The accepted client connection or null if no client was found.
     */
    private Socket accept() {
        try {
            return this.socket.accept();
        } catch (final SocketTimeoutException e) {
            return null;
        } catch (final IOException e) {
            LOG.error("Unable to accept new connection: " + e, e);
            return null;
        }
    }

    /**
     * Starts the server.
     */
    public final void start() {
        if (this.thread != null)
            throw new IllegalStateException("Thread already started");
        this.thread = new Thread(this);
        this.stop = false;
        this.thread.start();
    }

    /**
     * Stops the server.
     */
    public final void stop() {
        if (this.thread == null)
            throw new IllegalStateException("Thread already stopped");
        if (this.stop)
            throw new IllegalStateException("Thread already stopping");
        this.stop = true;
    }

    /**
     * @see java.lang.Runnable#run()
     */
    @Override
    public final void run() {
        try {
            while (!this.stop) {
                // Accept the next client. If timeout occurred then do nothing in
                // this thread iteration.
                final Socket socket = accept();
                if (socket == null)
                    continue;

                // Start new client thread
                new Thread(new OneInstanceClient(socket, this.appId)).start();
            }
        } finally {
            this.thread = null;
        }
    }
}