001/**
002 * Logback: the reliable, generic, fast and flexible logging framework.
003 * Copyright (C) 1999-2015, QOS.ch. All rights reserved.
004 *
005 * This program and the accompanying materials are dual-licensed under
006 * either the terms of the Eclipse Public License v1.0 as published by
007 * the Eclipse Foundation
008 *
009 *   or (per the licensee's choosing)
010 *
011 * under the terms of the GNU Lesser General Public License version 2.1
012 * as published by the Free Software Foundation.
013 */
014package ch.qos.logback.core.net.server.test;
015
016import java.io.IOException;
017import java.net.BindException;
018import java.net.ServerSocket;
019
020import javax.net.ServerSocketFactory;
021
022/**
023 * Static utility methods for obtaining a {@link ServerSocket} bound to
024 * a random unused port.
025 *
026 * @author Carl Harris
027 */
028public class ServerSocketUtil {
029
030    /**
031     * Creates a new {@link ServerSocket} bound to a random unused port.
032     * <p>
033     * This method is a convenience overload for 
034     * {@link #createServerSocket(ServerSocketFactory)} using the platform's
035     * default {@link ServerSocketFactory}.
036     * @return socket
037     * @throws IOException
038     */
039    public static ServerSocket createServerSocket() throws IOException {
040        return createServerSocket(ServerSocketFactory.getDefault());
041    }
042
043    /**
044     * Creates a new {@link ServerSocket} bound to a random unused port.
045     * @param socketFactory socket factory that will be used to create the 
046     *    socket
047     * @return socket
048     * @throws IOException
049     */
050    public static ServerSocket createServerSocket(ServerSocketFactory socketFactory) throws IOException {
051        ServerSocket socket = null;
052        int retries = 10;
053        while (retries-- > 0 && socket == null) {
054            int port = (int) ((65536 - 1024) * Math.random()) + 1024;
055            try {
056                socket = socketFactory.createServerSocket(port);
057            } catch (BindException ex) {
058                // try again with different port
059            }
060        }
061        if (socket == null) {
062            throw new BindException("cannot find an unused port to bind");
063        }
064        return socket;
065    }
066
067}