/*
    *   @(#) $Id: AvailablePortFinder.java 210062 2005-07-11 03:52:38Z trustin $
    * 
    *   Copyright 2004 The Apache Software Foundation
    *
    *   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.
   *
   */
  package org.apache.mina.util;
  
  import java.io.IOException;
  import java.net.DatagramSocket;
  import java.net.ServerSocket;
  import java.util.NoSuchElementException;
  import java.util.Set;
  import java.util.TreeSet;
  
  
  /***
   * Finds currently available server ports.
   *
   * @author The Apache Directory Project
   * @version $Rev: 210062 $
   * @see <a href="http://www.iana.org/assignments/port-numbers">IANA.org</a>
   */
  public class AvailablePortFinder
  {
      /***
       * The minimum number of server port number.
       */
      public static final int MIN_PORT_NUMBER = 1;
  
      /***
       * The maximum number of server port number.
       */
      public static final int MAX_PORT_NUMBER = 49151;
  
      /***
       * Creates a new instance.
       */
      private AvailablePortFinder()
      {
      }
  
      /***
       * Returns the {@link Set} of currently available port numbers
       * ({@link Integer}).  This method is identical to
       * <code>getAvailablePorts(MIN_PORT_NUMBER, MAX_PORT_NUMBER)</code>.
       *
       * WARNING: this can take a very long time.
       */
      public static Set getAvailablePorts()
      {
          return getAvailablePorts(MIN_PORT_NUMBER, MAX_PORT_NUMBER);
      }
  
      /***
       * Gets the next available port starting at the lowest port number.
       *
       * @throws NoSuchElementException if there are no ports available
       */
      public static int getNextAvailable()
      {
          return getNextAvailable(MIN_PORT_NUMBER);
      }
  
      /***
       * Gets the next available port starting at a port.
       *
       * @param fromPort the port to scan for availability
       * @throws NoSuchElementException if there are no ports available
       */
      public static int getNextAvailable(int fromPort)
      {
          if ((fromPort < MIN_PORT_NUMBER) || (fromPort > MAX_PORT_NUMBER))
          {
              throw new IllegalArgumentException("Invalid start port: "
                                                 + fromPort);
          }
  
          for (int i = fromPort; i <= MAX_PORT_NUMBER; i++)
          {
              ServerSocket ss = null;
              DatagramSocket ds = null;
              try
              {
                  ss = new ServerSocket(i);
                  ds = new DatagramSocket(i);
                  return i;
             }
             catch (IOException e)
             {
             }
             finally
             {
                 if (ds != null)
                 {
                     ds.close();
                 }
 
                 if (ss != null)
                 {
                     try
                     {
                         ss.close();
                     }
                     catch (IOException e)
                     {
                         /* should not be thrown */
                     }
                 }
             }
         }
 
         throw new NoSuchElementException("Could not find an available port "
                                          + "above " + fromPort);
     }
 
     /***
      * Checks to see if a specific port is available.
      *
      * @param port the port to check for availability
      */
     public static boolean available( int port )
     {
         if ( ( port < MIN_PORT_NUMBER) || ( port > MAX_PORT_NUMBER ) )
         {
             throw new IllegalArgumentException( "Invalid start port: " + port );
         }
 
         ServerSocket s = null;
         try
         {
             s = new ServerSocket( port );
             return true;
         }
         catch ( IOException e )
         {
             return false;
         }
         finally
         {
             if ( s != null )
             {
                 try
                 {
                     s.close();
                 }
                 catch (IOException e)
                 {
                     /* should not be thrown */
                 }
             }
         }
     }
 
     /***
      * Returns the {@link Set} of currently avaliable port numbers ({@link Integer})
      * between the specified port range.
      *
      * @throws IllegalArgumentException if port range is not between
      * {@link #MIN_PORT_NUMBER} and {@link #MAX_PORT_NUMBER} or
      * <code>fromPort</code> if greater than <code>toPort</code>.
      */
     public static Set getAvailablePorts(int fromPort, int toPort)
     {
         if (
             (fromPort < MIN_PORT_NUMBER) || (toPort > MAX_PORT_NUMBER)
                 || (fromPort > toPort))
         {
             throw new IllegalArgumentException("Invalid port range: "
                                                + fromPort + " ~ " + toPort);
         }
 
         Set result = new TreeSet();
 
         for (int i = fromPort; i <= toPort; i++)
         {
             ServerSocket s = null;
 
             try
             {
                 s = new ServerSocket(i);
                 result.add(new Integer(i));
             }
             catch (IOException e)
             {
             }
             finally
             {
                 if (s != null)
                 {
                     try
                     {
                         s.close();
                     }
                     catch (IOException e)
                     {
                         /* should not be thrown */
                     }
                 }
             }
         }
 
         return result;
     }
 }