001    /**
002     * Licensed to the Apache Software Foundation (ASF) under one or more
003     * contributor license agreements.  See the NOTICE file distributed with
004     * this work for additional information regarding copyright ownership.
005     * The ASF licenses this file to You under the Apache License, Version 2.0
006     * (the "License"); you may not use this file except in compliance with
007     * the License.  You may obtain a copy of the License at
008     *
009     *      http://www.apache.org/licenses/LICENSE-2.0
010     *
011     * Unless required by applicable law or agreed to in writing, software
012     * distributed under the License is distributed on an "AS IS" BASIS,
013     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014     * See the License for the specific language governing permissions and
015     * limitations under the License.
016     */
017    package org.apache.camel.test;
018    
019    import java.io.IOException;
020    import java.net.DatagramSocket;
021    import java.net.ServerSocket;
022    import java.util.NoSuchElementException;
023    
024    /**
025     * Finds currently available server ports.
026     *
027     * @see <a href="http://www.iana.org/assignments/port-numbers">IANA.org</a>
028     */
029    public final class AvailablePortFinder {
030        /**
031         * The minimum server port number. Set at 1024 to avoid returning privileged
032         * port numbers.
033         */
034        public static final int MIN_PORT_NUMBER = 1024;
035    
036        /**
037         * The maximum server port number.
038         */
039        public static final int MAX_PORT_NUMBER = 49151;
040    
041        /**
042         * Creates a new instance.
043         */
044        private AvailablePortFinder() {
045            // Do nothing
046        }
047    
048        /**
049         * Gets the next available port starting at the lowest port number.
050         *
051         * @throws NoSuchElementException if there are no ports available
052         */
053        public static int getNextAvailable() {
054            return getNextAvailable(MIN_PORT_NUMBER);
055        }
056    
057        /**
058         * Gets the next available port starting at a port.
059         *
060         * @param fromPort the port to scan for availability
061         * @throws NoSuchElementException if there are no ports available
062         */
063        public static int getNextAvailable(int fromPort) {
064            if (fromPort < MIN_PORT_NUMBER || fromPort > MAX_PORT_NUMBER) {
065                throw new IllegalArgumentException("Invalid start port: " + fromPort);
066            }
067    
068            for (int i = fromPort; i <= MAX_PORT_NUMBER; i++) {
069                if (available(i)) {
070                    return i;
071                }
072            }
073    
074            throw new NoSuchElementException("Could not find an available port above " + fromPort);
075        }
076    
077        /**
078         * Checks to see if a specific port is available.
079         *
080         * @param port the port to check for availability
081         */
082        public static boolean available(int port) {
083            if (port < MIN_PORT_NUMBER || port > MAX_PORT_NUMBER) {
084                throw new IllegalArgumentException("Invalid start port: " + port);
085            }
086    
087            ServerSocket ss = null;
088            DatagramSocket ds = null;
089            try {
090                ss = new ServerSocket(port);
091                ss.setReuseAddress(true);
092                ds = new DatagramSocket(port);
093                ds.setReuseAddress(true);
094                return true;
095            } catch (IOException e) {
096                // Do nothing
097            } finally {
098                if (ds != null) {
099                    ds.close();
100                }
101    
102                if (ss != null) {
103                    try {
104                        ss.close();
105                    } catch (IOException e) {
106                        /* should not be thrown */
107                    }
108                }
109            }
110    
111            return false;
112        }
113    }