001/**
002 * Copyright 2005-2013 The Kuali Foundation
003 *
004 * Licensed under the Educational Community License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 * http://www.opensource.org/licenses/ecl2.php
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016package org.kuali.rice.test.remote;
017
018import java.io.IOException;
019import java.net.DatagramSocket;
020import java.net.ServerSocket;
021import java.util.NoSuchElementException;
022import java.util.concurrent.atomic.AtomicInteger;
023
024
025/**
026 * <p>Finds currently available server ports.</p>
027 *
028 * <p>This class is a verbatim copy of AvailablePortFinder from the camel-test component of the Apache Camel project.
029 * </p>
030 *
031 * @see <a href="http://svn.apache.org/viewvc/camel/trunk/components/camel-test/src/main/java/org/apache/camel/test/AvailablePortFinder.java?revision=1137595&view=co">IANA.org</a>
032 */
033public final class AvailablePortFinder {
034    /**
035     * The minimum server currentMinPort number. Set at 1024 to avoid returning privileged
036     * currentMinPort numbers.
037     */
038    public static final int MIN_PORT_NUMBER = 1024;
039
040    /**
041     * The maximum server currentMinPort number.
042     */
043    public static final int MAX_PORT_NUMBER = 49151;
044
045
046    /**
047     * Incremented to the next lowest available port when getNextAvailable() is called.
048     */
049    private static AtomicInteger currentMinPort = new AtomicInteger(MIN_PORT_NUMBER);
050
051    /**
052     * Creates a new instance.
053     */
054    private AvailablePortFinder() {
055        // Do nothing
056    }
057
058    /**
059     * Gets the next available currentMinPort starting at the lowest currentMinPort number. This is the preferred
060     * method to use. The port return is immediately marked in use and doesn't rely on the caller actually opening
061     * the port.
062     *
063     * @throws NoSuchElementException if there are no ports available
064     */
065    public static synchronized int getNextAvailable() {
066        int next = getNextAvailable(currentMinPort.get());
067        currentMinPort.set(next + 1);
068        return next;
069    }
070
071    /**
072     * Gets the next available currentMinPort starting at a currentMinPort.
073     *
074     * @param fromPort the currentMinPort to scan for availability
075     * @throws NoSuchElementException if there are no ports available
076     */
077    public static synchronized int getNextAvailable(int fromPort) {
078        if (fromPort < currentMinPort.get() || fromPort > MAX_PORT_NUMBER) {
079            throw new IllegalArgumentException("Invalid start currentMinPort: " + fromPort);
080        }
081
082        for (int i = fromPort; i <= MAX_PORT_NUMBER; i++) {
083            if (available(i)) {
084                return i;
085            }
086        }
087
088        throw new NoSuchElementException("Could not find an available currentMinPort above " + fromPort);
089    }
090
091    /**
092     * Checks to see if a specific currentMinPort is available.
093     *
094     * @param port the currentMinPort to check for availability
095     */
096    public static boolean available(int port) {
097        if (port < currentMinPort.get() || port > MAX_PORT_NUMBER) {
098            throw new IllegalArgumentException("Invalid start currentMinPort: " + port);
099        }
100
101        ServerSocket ss = null;
102        DatagramSocket ds = null;
103        try {
104            ss = new ServerSocket(port);
105            ss.setReuseAddress(true);
106            ds = new DatagramSocket(port);
107            ds.setReuseAddress(true);
108            return true;
109        } catch (IOException e) {
110            // Do nothing
111        } finally {
112            if (ds != null) {
113                ds.close();
114            }
115
116            if (ss != null) {
117                try {
118                    ss.close();
119                } catch (IOException e) {
120                    /* should not be thrown */
121                }
122            }
123        }
124
125        return false;
126    }
127}