PortProber.java

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// regarding copyright ownership.  The SFC 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
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package org.jboss.arquillian.warp.impl.utils.net;

import org.jboss.arquillian.warp.impl.utils.Platform;

import java.io.IOException;
import java.net.ConnectException;
import java.net.InetSocketAddress;
import java.net.ServerSocket;
import java.net.Socket;
import java.net.UnknownHostException;
import java.util.Random;
import java.util.concurrent.Callable;
import java.util.concurrent.TimeUnit;

import static java.lang.Math.max;
import static java.util.concurrent.TimeUnit.SECONDS;

public class PortProber {

    private static final Random random = new Random();
    private static final EphemeralPortRangeDetector ephemeralRangeDetector;

    static {
        final Platform current = Platform.getCurrent();

        if (current.is(Platform.LINUX)) {
            ephemeralRangeDetector = LinuxEphemeralPortRangeDetector.getInstance();
        } else if (current.is(Platform.XP)) {
            ephemeralRangeDetector = new OlderWindowsVersionEphemeralPortDetector();
        } else {
            ephemeralRangeDetector = new FixedIANAPortRange();
        }
    }

    public static final int HIGHEST_PORT = 65535;
    public static final int START_OF_USER_PORTS = 1024;

    private PortProber() {
        // Utility class
    }

    public static int findFreePort() {
        for (int i = 0; i < 5; i++) {
            int seedPort = createAcceptablePort();
            int suggestedPort = checkPortIsFree(seedPort);
            if (suggestedPort != -1) {
                return suggestedPort;
            }
        }
        throw new RuntimeException("Unable to find a free port");
    }

    public static Callable<Integer> freeLocalPort(final int port) {
        return new Callable<Integer>() {

            public Integer call()
                throws Exception {
                if (checkPortIsFree(port) != -1) {
                    return port;
                }
                return null;
            }
        };
    }

    /**
     * Returns a port that is within a probable free range. <p/> Based on the ports in
     * http://en.wikipedia.org/wiki/Ephemeral_ports, this method stays away from all well-known
     * ephemeral port ranges, since they can arbitrarily race with the operating system in
     * allocations. Due to the port-greedy nature of selenium this happens fairly frequently.
     * Staying within the known safe range increases the probability tests will run green quite
     * significantly.
     *
     * @return a random port number
     */
    private static int createAcceptablePort() {
        synchronized (random) {
            final int FIRST_PORT;
            final int LAST_PORT;

            int freeAbove = HIGHEST_PORT - ephemeralRangeDetector.getHighestEphemeralPort();
            int freeBelow = max(0, ephemeralRangeDetector.getLowestEphemeralPort() - START_OF_USER_PORTS);

            if (freeAbove > freeBelow) {
                FIRST_PORT = ephemeralRangeDetector.getHighestEphemeralPort();
                LAST_PORT = 65535;
            } else {
                FIRST_PORT = 1024;
                LAST_PORT = ephemeralRangeDetector.getLowestEphemeralPort();
            }

            if (FIRST_PORT == LAST_PORT) {
                return FIRST_PORT;
            }
            if (FIRST_PORT > LAST_PORT) {
                throw new UnsupportedOperationException("Could not find ephemeral port to use");
            }
            final int randomInt = random.nextInt();
            final int portWithoutOffset = Math.abs(randomInt % (LAST_PORT - FIRST_PORT + 1));
            return portWithoutOffset + FIRST_PORT;
        }
    }

    private static int checkPortIsFree(int port) {
        ServerSocket socket;
        try {
            socket = new ServerSocket();
            socket.setReuseAddress(true);
            socket.bind(new InetSocketAddress("localhost", port));
            int localPort = socket.getLocalPort();
            socket.close();
            return localPort;
        } catch (IOException e) {
            return -1;
        }
    }

    public static boolean pollPort(int port) {
        return pollPort(port, 15, SECONDS);
    }

    public static boolean pollPort(int port, int timeout, TimeUnit unit) {
        long end = System.currentTimeMillis() + unit.toMillis(timeout);
        while (System.currentTimeMillis() < end) {
            try {
                Socket socket = new Socket();
                socket.setReuseAddress(true);
                socket.bind(new InetSocketAddress("localhost", port));
                socket.close();
                return true;
            } catch (ConnectException e) {
                // Ignore this
            } catch (UnknownHostException e) {
                throw new RuntimeException(e);
            } catch (IOException e) {
                throw new RuntimeException(e);
            }
        }

        return false;
    }
}