Java HTTP Port Find randomFreePort()

Description

Returns a random free port and marks that port as taken.

License

Apache License

Declaration

public static int randomFreePort() 

Method Source Code

//package com.java2s;
/**/*w w  w.j  a  v  a  2 s.  c  o m*/
 * 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.
 */

import java.io.IOException;

import java.net.ServerSocket;

import java.util.HashSet;

import java.util.Random;
import java.util.Set;

public class Main {
    /** A set of ports that have been claimed using {@link #randomFreePort()}. */
    private static final Set<Integer> takenRandomPorts = new HashSet<Integer>();
    private static final int MIN_RANDOM_PORT = 0xc000;
    private static final int MAX_RANDOM_PORT = 0xfffe;
    private static Random random = new Random();

    /**
     * Returns a random free port and marks that port as taken. Not thread-safe. Expected to be
     * called from single-threaded test setup code/
     */
    public static int randomFreePort() {
        int port = 0;
        do {
            port = randomPort();
            if (takenRandomPorts.contains(port)) {
                port = 0;
                continue;
            }
            takenRandomPorts.add(port);

            try {
                ServerSocket sock = new ServerSocket(port);
                sock.close();
            } catch (IOException ex) {
                port = 0;
            }
        } while (port == 0);
        return port;
    }

    /**
     * Returns a random port. These ports cannot be registered with IANA and are
     * intended for dynamic allocation (see http://bit.ly/dynports).
     */
    public static int randomPort() {
        return MIN_RANDOM_PORT + random.nextInt(MAX_RANDOM_PORT - MIN_RANDOM_PORT);
    }
}

Related

1. parseHostPort(String s)
2. parsePort(String s)
3. ping(String domain, int port)
4. pingServer(String host, Integer port)
5. randomAvailablePort()
6. randomFreePort()
7. randomFreePort()
8. read(String host, int port)
9. readHttpContent(String domain, String resource, int port)