| /** |
| * 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. |
| */ |
| |
| package org.apache.hadoop.hdfsproxy; |
| |
| import java.net.ServerSocket; |
| import java.io.IOException; |
| import java.net.BindException; |
| import java.util.Random; |
| |
| public class FindFreePort { |
| private static final int MIN_AVAILABLE_PORT = 10000; |
| private static final int MAX_AVAILABLE_PORT = 65535; |
| private static Random random = new Random(); |
| /** |
| * |
| * @param num <= 0, find a single free port |
| * @return free port next to port (>port) |
| * @throws IOException |
| */ |
| public static int findFreePort(int port) throws IOException { |
| ServerSocket server; |
| if (port < 0) { |
| server = new ServerSocket(0); |
| } else { |
| int freePort = port+1; |
| while (true) { |
| try { |
| server = new ServerSocket(freePort); |
| break; |
| } catch (IOException e) { |
| if (e instanceof BindException) { |
| if (freePort >= MAX_AVAILABLE_PORT || |
| freePort < MIN_AVAILABLE_PORT) { |
| throw e; |
| } |
| } else { |
| throw e; |
| } |
| freePort += 1; |
| } |
| } |
| } |
| int fport = server.getLocalPort(); |
| server.close(); |
| return fport; |
| } |
| /** |
| * |
| * @return |
| * @throws IOException |
| */ |
| public static int findFreePortRandom() throws IOException { |
| return findFreePort(MIN_AVAILABLE_PORT + random.nextInt(MAX_AVAILABLE_PORT - MIN_AVAILABLE_PORT + 1)); |
| } |
| |
| |
| public static void main(String[] args) throws Exception { |
| if(args.length < 1) { |
| System.err.println("Usage: FindFreePort < -random / <#port> >"); |
| System.exit(0); |
| } |
| int j = 0; |
| String cmd = args[j++]; |
| if ("-random".equals(cmd)) { |
| System.out.println(findFreePortRandom()); |
| } else { |
| System.out.println(findFreePort(Integer.parseInt(cmd))); |
| } |
| } |
| |
| } |