net.sourceforge.phpeclipse.debug.core/src/net/sourceforge/phpdt/internal/debug/core/SocketUtil.java

   1 /**********************************************************************
   2  Copyright (c) 2000, 2002 IBM Corp. and others.
   3  All rights reserved. This program and the accompanying materials
   4  are made available under the terms of the Common Public License v1.0
   5  which accompanies this distribution, and is available at
   6  http://www.eclipse.org/legal/cpl-v10.html
   7
   8  Contributors:
   9  IBM Corporation - Initial implementation
  10  Vicente Fernando - www.alfersoft.com.ar
  11  **********************************************************************/
  12 package net.sourceforge.phpdt.internal.debug.core;
  13
  14 import java.io.IOException;
  15 import java.net.ConnectException;
  16 import java.net.Socket;
  17 import java.util.Random;
  18
  19 /**
  20  * Utility class to find a port to debug on.
  21  */
  22 public class SocketUtil {
  23         private static final Random fgRandom = new Random(System
  24                         .currentTimeMillis());
  25
  26         /**
  27          * Returns a free port number on the specified host within the given range,
  28          * or -1 if none found.
  29          *
  30          * @param host
  31          *            name or IP addres of host on which to find a free port
  32          * @param searchFrom
  33          *            the port number from which to start searching
  34          * @param searchTo
  35          *            the port number at which to stop searching
  36          * @return a free port in the specified range, or -1 of none found
  37          */
  38         public static int findUnusedLocalPort(String host, int searchFrom,
  39                         int searchTo) {
  40
  41                 // First look at the five first ports starting on searchFrom
  42                 for (int i = searchFrom; i <= searchFrom + 5; i++) {
  43                         Socket s = null;
  44                         int port = i;
  45                         try {
  46                                 s = new Socket(host, port);
  47                         } catch (ConnectException e) {
  48                                 return port;
  49                         } catch (IOException e) {
  50                         } finally {
  51                                 if (s != null) {
  52                                         try {
  53                                                 s.close();
  54                                         } catch (IOException ioe) {
  55                                         }
  56                                 }
  57                         }
  58                 }
  59                 // No free port found then look at 5 random ports numbers
  60                 for (int i = 0; i < 5; i++) {
  61                         Socket s = null;
  62                         int port = getRandomPort(searchFrom, searchTo);
  63                         try {
  64                                 s = new Socket(host, port);
  65                         } catch (ConnectException e) {
  66                                 return port;
  67                         } catch (IOException e) {
  68                         } finally {
  69                                 if (s != null) {
  70                                         try {
  71                                                 s.close();
  72                                         } catch (IOException ioe) {
  73                                         }
  74                                 }
  75                         }
  76                 }
  77                 return -1;
  78         }
  79
  80         private static int getRandomPort(int low, int high) {
  81                 return (int) (fgRandom.nextFloat() * (high - low)) + low;
  82         }
  83 }