Java HTTP Port Find randomFreePort()

Description

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

License

Open Source License

Declaration

public static int randomFreePort() 

Method Source Code

//package com.java2s;
//License from project: Open Source License 

import java.io.IOException;
import java.net.DatagramSocket;
import java.net.ServerSocket;
import java.util.Random;

public class Main {
    private static final int MIN_RANDOM_PORT = 0xc000;
    private static final int MAX_RANDOM_PORT = 0xfffe;
    private static Random random = new Random();

    /**//  ww w .j  a v a2 s .c  o m
     * Returns a random free port and marks that port as taken. Not thread-safe. Expected to be called from
     * single-threaded test setup code nc -l portno can be used to verify the results
     */
    public static int randomFreePort() {
        int port = 0;
        boolean portAvailable = true;
        ;
        do {
            port = randomPort();
            portAvailable = available(port);
        } while (!portAvailable);
        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);
    }

    /**
     * Checks to see if a specific port is available(Bind is not called). setReuseAddress has been enabled to have port
     * reusability in case of TIME_WAIT.
     * 
     * @param port the port number to check for availability
     * @return <tt>true</tt> if the port is available, or <tt>false</tt> if not
     */
    public static boolean available(int port) {
        ServerSocket ss = null;
        DatagramSocket ds = null;
        try {
            ss = new ServerSocket(port);
            ss.setReuseAddress(true);
            ds = new DatagramSocket(port);
            ds.setReuseAddress(true);
            return true;
        } catch (IOException e) {
            // Do nothing
        } finally {
            if (ds != null) {
                ds.close();
            }

            if (ss != null) {
                try {
                    ss.close();
                } catch (IOException e) {
                    /* should not be thrown */
                }
            }
        }

        return false;
    }
}

Related

1. ping(String domain, int port)
2. pingServer(String host, Integer port)
3. randomAvailablePort()
4. randomFreePort()
5. randomFreePort()
6. read(String host, int port)
7. readHttpContent(String domain, String resource, int port)
8. replace(final String host, final int port, final String user, final String program, final String relation, final String dataset, final String format)
9. resolve(final String desc, final int defaultPort)