Java HTTP Port Find getFreePort()

Description

Get a free local port.

License

Apache License

Return

the port.

Declaration

static public int getFreePort() 

Method Source Code

//package com.java2s;
/*//w ww .  j  a v a2s  . c o  m
 * Copyright (C) IBM Corp. 2009.
 * 
 * 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;

public class Main {
    /**
     * Get a free local port.  Used to setup communication between job controller and Mapper/Reducer.
     * @return the port.
     */
    static public int getFreePort() {
        ServerSocket ss;
        int freePort = 0;

        for (int i = 0; i < 10; i++) {
            freePort = (int) (10000 + Math.round(Math.random() * 10000));
            freePort = freePort % 2 == 0 ? freePort : freePort + 1;
            try {
                ss = new ServerSocket(freePort);
                freePort = ss.getLocalPort();
                ss.close();
                return freePort;
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

        try {
            ss = new ServerSocket(0);
            freePort = ss.getLocalPort();
            ss.close();
        } catch (IOException e) {
            e.printStackTrace();
        }

        return freePort;
    }
}

Related

1. getFreePort()
2. getFreePort()
3. getFreePort()
4. getFreePort()
5. getFreePort()
6. getFreePort()
7. getFreePort(int port)
8. getFreePort(int pPort)
9. getFreePortNoSych()