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.currentTimeMillis());
  24
  25         /**
  26          * Returns a free port number on the specified host within the given range,
  27          * or -1 if none found.
  28          *
  29          * @param host name or IP addres of host on which to find a free port
  30          * @param searchFrom the port number from which to start searching
  31          * @param searchTo the port number at which to stop searching
  32          * @return a free port in the specified range, or -1 of none found
  33          */
  34         public static int findUnusedLocalPort(String host, int searchFrom, int searchTo) {
  35
  36                 // First look at the five first ports starting on searchFrom
  37                 for (int i= searchFrom; i <= searchFrom + 5; i++) {
  38                         Socket s= null;
  39                         int port= i;
  40                         try {
  41                                 s= new Socket(host, port);
  42                         } catch (ConnectException e) {
  43                                 return port;
  44                         } catch (IOException e) {
  45                         } finally {
  46                                 if (s != null) {
  47                                         try {
  48                                                 s.close();
  49                                         } catch (IOException ioe) {
  50                                         }
  51                                 }
  52                         }
  53                 }
  54                 // No free port found then look at 5 random ports numbers
  55                 for (int i= 0; i < 5; i++) {
  56                         Socket s= null;
  57                         int port= getRandomPort(searchFrom, searchTo);
  58                         try {
  59                                 s= new Socket(host, port);
  60                         } catch (ConnectException e) {
  61                                 return port;
  62                         } catch (IOException e) {
  63                         } finally {
  64                                 if (s != null) {
  65                                         try {
  66                                                 s.close();
  67                                         } catch (IOException ioe) {
  68                                         }
  69                                 }
  70                         }
  71                 }
  72                 return -1;
  73         }
  74
  75         private static int getRandomPort(int low, int high) {
  76                 return (int)(fgRandom.nextFloat() * (high-low)) + low;
  77         }
  78 }