Java HTTP Port Find getAvailablePort(int startPort)

Description

Find the first available port after a given port

License

Open Source License

Return

an available port

Declaration

public static synchronized int getAvailablePort(int startPort) 

Method Source Code

//package com.java2s;
/*//  w  ww. j  a v a  2 s.  c o m
 *
 * Copyright 2013 LinkedIn Corp. All rights reserved
 *
 * 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.DatagramSocket;

import java.net.ServerSocket;

import java.util.HashSet;
import java.util.Set;

public class Main {
    /**
     * The set of ports assigned by {@link #getAvailablePort(int)}. This is to avoid race conditions
     * by different tests using the same port.
     */
    private static final Set<Integer> _assignedPorts = new HashSet<Integer>();

    /**
     * Find the first available port after a given port
     * @return an available port
     **/
    public static synchronized int getAvailablePort(int startPort) {
        int port = startPort;

        while (_assignedPorts.contains(port) && !portAvailable(port) && port < 0x7FFFFFFF) {
            port++;
        }

        if (0x7FFFFFFF == port) {
            throw new RuntimeException("no available port found starting at " + startPort);
        }

        _assignedPorts.add(port);
        return port;
    }

    /**
     * Checks to see if a specific port is available.
     *
     * @param port the port to check for availability
     */
    public static boolean portAvailable(int port) {
        if (port < 1200 || port > 65000) {
            throw new IllegalArgumentException("Invalid start port: " + 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) {
        } finally {
            if (ds != null) {
                ds.close();
            }

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

        return false;
    }
}

Related

1. getAvailablePort(int defaultPort)
2. getAvailablePort(int port)
3. getAvailablePort(int port)
4. getAvailablePort(int prefferedPort)
5. getAvailablePort(int randomAttempts)
6. getAvailablePort(String hostname, String portRange)
7. getAvailablePorts(int basePort, int portCount)
8. getAvailablePortsFromRange(int portMin, int portMax, int numberOfPorts)
9. getAvialablePort(final int basePort)