dotnet/src/WebDriver/Internal/PortUtilities.cs

// <copyright file="PortUtilities.cs" company="WebDriver Committers">
// Copyright 2007-2012 WebDriver committers
// Copyright 2007-2012 Google Inc.
// Portions copyright 2012 Software Freedom Conservancy
//
// 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.
// </copyright>

using System;
using System.Collections.Generic;
using System.Net;
using System.Net.Sockets;
using System.Text;

namespace OpenQA.Selenium.Internal
{
    /// <summary>
    /// Encapsulates methods for working with ports.
    /// </summary>
    internal static class PortUtilities
    {
        /// <summary>
        /// Finds a random, free port to be listened on.
        /// </summary>
        /// <returns>A random, free port to be listened on.</returns>
        public static int FindFreePort()
        {
            // Locate a free port on the local machine by binding a socket to
            // an IPEndPoint using IPAddress.Any and port 0. The socket will
            // select a free port.
            int listeningPort = 0;
            Socket portSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
            try
            {
                IPEndPoint socketEndPoint = new IPEndPoint(IPAddress.Any, 0);
                portSocket.Bind(socketEndPoint);
                socketEndPoint = (IPEndPoint)portSocket.LocalEndPoint;
                listeningPort = socketEndPoint.Port;
            }
            finally
            {
                portSocket.Close();
            }

            return listeningPort;
        }
    }
}