Java HTTP Port Find getRandomPorts(int n)

Description

Create a list of currently available port numbers as strings.

License

Apache License

Parameter

Parameter	Description
n	number of ports to find

Exception

Parameter	Description
IOException	an exception

Return

list of available ports

Declaration

public static List<String> getRandomPorts(int n) throws IOException 

Method Source Code

//package com.java2s;
/*//from  w w  w  .  jav a  2  s .c  o  m
 * Copyright 2017 StreamSets Inc.
 *
 * Licensed 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.ArrayList;
import java.util.List;

public class Main {
    /**
     * Create a list of currently available port numbers as strings.
     *
     * This simply calls {@link NetworkUtils#getRandomPort()} n times to build a list.
     * The same caveats apply as not all ports may still be available upon attempted use.
     *
     * @param n number of ports to find
     * @return list of available ports
     * @throws IOException
     */
    public static List<String> getRandomPorts(int n) throws IOException {
        List<String> ports = new ArrayList<>();
        for (int i = 0; i < n; i++) {
            ports.add(String.valueOf(getRandomPort()));
        }
        return ports;
    }

    /**
     * Create port number that is available on this machine for
     * subsequent use.
     *
     * Please note that this method doesn't guarantee that you
     * will be able to subsequently use that port as there is
     * a race condition when this method can return port number
     * that is available at the time of the call, but will be
     * used by different process before the caller will have a
     * chance to use it.
     *
     * This is merely a helper method to find a random available
     * port on the machine to enable multiple text executions
     * on the same machine or deal with situation when some tools
     * (such as Derby) do need specific port and can't be started
     * on "random" port.
     *
     * @return Available port number
     */
    public static int getRandomPort() {
        try (ServerSocket ss = new ServerSocket(0)) {
            return ss.getLocalPort();
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
    }
}

Related

1. getRandomFreePort()
2. getRandomOpenPort()
3. getRandomPort()
4. getRandomPort()
5. getRandomPort()
6. getResponse(String name, String host, int port)
7. getServerPort()
8. getSupportedConnectionTypes(Map map)
9. getSupportedEntityTypes()