# FreePortFinder.java

    /*
     * Copyright (c) 2012, Paul Merlin.
     *
     * 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.qi4j.test.util;

    import java.io.IOException;
    import java.net.InetAddress;
    import java.net.ServerSocket;

    public class FreePortFinder
    {

        public static int findFreePortOnLoopback()
                throws IOException
        {
            return findFreePortOnIface( InetAddress.getLocalHost() );
        }

        public static int findFreePortOnLoopback( int prefered )
                throws IOException
        {
            return findFreePortOnIface( InetAddress.getLocalHost(), prefered );
        }

        public static int findFreePortOnIface( InetAddress address )
                throws IOException
        {
            return findFreePortOnIface( address, -1 );
        }

        public static int findFreePortOnIface( InetAddress address, int prefered )
                throws IOException
        {
            ServerSocket server;
            if ( prefered > 0 ) {
                server = new ServerSocket( prefered, 1, address );
            } else {
                server = new ServerSocket( 0, 1, address );
            }
            int port = server.getLocalPort();
            server.close();
            return port;
        }

    }