AvailablePortFinder.java

/*
 *  Licensed to the Apache Software Foundation (ASF) under one
 *  or more contributor license agreements.  See the NOTICE file
 *  distributed with this work for additional information
 *  regarding copyright ownership.  The ASF licenses this file
 *  to you under the Apache License, Version 2.0 (the
 *  "License"); you may not use this file except in compliance
 *  with the License.  You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing,
 *  software distributed under the License is distributed on an
 *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 *  KIND, either express or implied.  See the License for the
 *  specific language governing permissions and limitations
 *  under the License.
 */
package org.apache.usergrid.persistence.core.util;


import java.io.IOException;
import java.net.DatagramSocket;
import java.net.ServerSocket;
import java.util.NoSuchElementException;
import java.util.Set;
import java.util.TreeSet;


/**
 * Finds currently available server ports.
 *
 * @author <a href="http://mina.apache.org">Apache MINA Project</a>
 * @see <a href="http://www.iana.org/assignments/port-numbers">IANA.org</a>
 * 
 * TODO: move this to test packages once Query Index uses it correctly.
 */
public class AvailablePortFinder {
    /** The minimum number of server port number. */
    public static final int MIN_PORT_NUMBER = 1;

    /** The maximum number of server port number. */
    public static final int MAX_PORT_NUMBER = 49151;


    /** Creates a new instance. */
    private AvailablePortFinder() {
        // Do nothing
    }


    /**
     * Returns the {@link java.util.Set} of currently available port numbers ({@link Integer}).  This method is identical to
     * <code>getAvailablePorts(MIN_PORT_NUMBER, MAX_PORT_NUMBER)</code>.
     * <p/>
     * WARNING: this can take a very long time.
     */
    public static Set<Integer> getAvailablePorts() {
        return getAvailablePorts( MIN_PORT_NUMBER, MAX_PORT_NUMBER );
    }


    /**
     * Gets an available port, MAY be outside of MIN_PORT_NUMBER to MAX_PORT_NUMBER range. 
     *
     * @throws java.util.NoSuchElementException if there are no ports available
     */
    public static int getNextAvailable() {
        ServerSocket serverSocket = null;

        try {
            // Here, we simply return an available port found by the system
            serverSocket = new ServerSocket( 0 );
            int port = serverSocket.getLocalPort();

            // Don't forget to close the socket...
            serverSocket.close();

            return port;
        }
        catch ( IOException ioe ) {
            throw new NoSuchElementException( ioe.getMessage() );
        }
    }


    /**
     * Gets the next available port starting at a port.
     *
     * @param fromPort the port to scan for availability
     *
     * @throws java.util.NoSuchElementException if there are no ports available
     */
    public static int getNextAvailable( int fromPort ) {
        if ( fromPort < MIN_PORT_NUMBER || fromPort > MAX_PORT_NUMBER ) {
            throw new IllegalArgumentException( "Invalid start port: " + fromPort );
        }

        for ( int i = fromPort; i <= MAX_PORT_NUMBER; i++ ) {
            if ( available( i ) ) {
                return i;
            }
        }

        throw new NoSuchElementException( "Could not find an available port " + "above " + fromPort );
    }


    /**
     * Checks to see if a specific port is available.
     *
     * @param port the port to check for availability
     */
    public static boolean available( int port ) {
        if ( port < MIN_PORT_NUMBER || port > MAX_PORT_NUMBER ) {
            throw new IllegalArgumentException( "Invalid start port: " + port );
        }

        ServerSocket ss = null;
        DatagramSocket ds = null;

        try {
            ss = new ServerSocket( port );
            ss.setReuseAddress( true );
            ds = new DatagramSocket( port );
            ds.setReuseAddress( true );
            return true;
        }
        catch ( IOException e ) {
            // Do nothing
        }
        finally {
            if ( ds != null ) {
                ds.close();
            }

            if ( ss != null ) {
                try {
                    ss.close();
                }
                catch ( IOException e ) {
                    /* should not be thrown */
                }
            }
        }

        return false;
    }


    /**
     * Returns the {@link java.util.Set} of currently avaliable port numbers ({@link Integer}) between the specified port range.
     *
     * @throws IllegalArgumentException if port range is not between {@link #MIN_PORT_NUMBER} and {@link
     * #MAX_PORT_NUMBER} or <code>fromPort</code> if greater than <code>toPort</code>.
     */
    public static Set<Integer> getAvailablePorts( int fromPort, int toPort ) {
        if ( fromPort < MIN_PORT_NUMBER || toPort > MAX_PORT_NUMBER || fromPort > toPort ) {
            throw new IllegalArgumentException( "Invalid port range: " + fromPort + " ~ " + toPort );
        }

        Set<Integer> result = new TreeSet<Integer>();

        for ( int i = fromPort; i <= toPort; i++ ) {
            ServerSocket s = null;

            try {
                s = new ServerSocket( i );
                result.add( new Integer( i ) );
            }
            catch ( IOException e ) {
                // Do nothing
            }
            finally {
                if ( s != null ) {
                    try {
                        s.close();
                    }
                    catch ( IOException e ) {
                        /* should not be thrown */
                    }
                }
            }
        }

        return result;
    }
}