#region License
/*
 * WebSocketServer.cs
 *
 * A C# implementation of the WebSocket protocol server.
 *
 * The MIT License
 *
 * Copyright (c) 2012-2015 sta.blockhead
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
#endregion

#region Contributors
/*
 * Contributors:
 * - Juan Manuel Lallana <juan.manuel.lallana@gmail.com>
 * - Jonas Hovgaard <j@jhovgaard.dk>
 * - Liryna <liryna.stark@gmail.com>
 * - Rohan Singh <rohan-singh@hotmail.com>
 */
#endregion

using System;
using System.Collections.Generic;
using System.Net.Sockets;
using System.Security.Cryptography.X509Certificates;
using System.Security.Principal;
using System.Text;
using System.Threading;
using WebSocketSharp.Net;
using WebSocketSharp.Net.WebSockets;

namespace WebSocketSharp.Server
{
  /// <summary>
  /// Provides a WebSocket protocol server.
  /// </summary>
  /// <remarks>
  /// The WebSocketServer class can provide multiple WebSocket services.
  /// </remarks>
  public class WebSocketServer
  {
    #region Private Fields

    private System.Net.IPAddress               _address;
    private AuthenticationSchemes              _authSchemes;
    private static readonly string             _defaultRealm;
    private bool                               _dnsStyle;
    private string                             _hostname;
    private TcpListener                        _listener;
    private Logger                             _logger;
    private int                                _port;
    private string                             _realm;
    private Thread                             _receiveThread;
    private bool                               _reuseAddress;
    private bool                               _secure;
    private WebSocketServiceManager            _services;
    private ServerSslConfiguration             _sslConfig;
    private volatile ServerState               _state;
    private object                             _sync;
    private Func<IIdentity, NetworkCredential> _userCredFinder;

    #endregion

    #region Static Constructor

    static WebSocketServer ()
    {
      _defaultRealm = "SECRET AREA";
    }

    #endregion

    #region Public Constructors

    /// <summary>
    /// Initializes a new instance of the <see cref="WebSocketServer"/> class.
    /// </summary>
    /// <remarks>
    /// An instance initialized by this constructor listens for the incoming connection requests on
    /// port 80.
    /// </remarks>
    public WebSocketServer ()
    {
      init (null, System.Net.IPAddress.Any, 80, false);
    }

    /// <summary>
    /// Initializes a new instance of the <see cref="WebSocketServer"/> class with
    /// the specified <paramref name="port"/>.
    /// </summary>
    /// <remarks>
    ///   <para>
    ///   An instance initialized by this constructor listens for the incoming connection requests
    ///   on <paramref name="port"/>.
    ///   </para>
    ///   <para>
    ///   If <paramref name="port"/> is 443, that instance provides a secure connection.
    ///   </para>
    /// </remarks>
    /// <param name="port">
    /// An <see cref="int"/> that represents the port number on which to listen.
    /// </param>
    /// <exception cref="ArgumentOutOfRangeException">
    /// <paramref name="port"/> isn't between 1 and 65535 inclusive.
    /// </exception>
    public WebSocketServer (int port)
      : this (port, port == 443)
    {
    }

    /// <summary>
    /// Initializes a new instance of the <see cref="WebSocketServer"/> class with
    /// the specified WebSocket URL.
    /// </summary>
    /// <remarks>
    ///   <para>
    ///   An instance initialized by this constructor listens for the incoming connection requests
    ///   on the host name and port in <paramref name="url"/>.
    ///   </para>
    ///   <para>
    ///   If <paramref name="url"/> doesn't include a port, either port 80 or 443 is used on
    ///   which to listen. It's determined by the scheme (ws or wss) in <paramref name="url"/>.
    ///   (Port 80 if the scheme is ws.)
    ///   </para>
    /// </remarks>
    /// <param name="url">
    /// A <see cref="string"/> that represents the WebSocket URL of the server.
    /// </param>
    /// <exception cref="ArgumentNullException">
    /// <paramref name="url"/> is <see langword="null"/>.
    /// </exception>
    /// <exception cref="ArgumentException">
    ///   <para>
    ///   <paramref name="url"/> is empty.
    ///   </para>
    ///   <para>
    ///   -or-
    ///   </para>
    ///   <para>
    ///   <paramref name="url"/> is invalid.
    ///   </para>
    /// </exception>
    public WebSocketServer (string url)
    {
      if (url == null)
        throw new ArgumentNullException ("url");

      if (url.Length == 0)
        throw new ArgumentException ("An empty string.", "url");

      Uri uri;
      string msg;
      if (!tryCreateUri (url, out uri, out msg))
        throw new ArgumentException (msg, "url");

      var host = uri.DnsSafeHost;
      var addr = host.ToIPAddress ();
      if (!addr.IsLocal ())
        throw new ArgumentException ("The host part isn't a local host name: " + url, "url");

      init (host, addr, uri.Port, uri.Scheme == "wss");
    }

    /// <summary>
    /// Initializes a new instance of the <see cref="WebSocketServer"/> class with
    /// the specified <paramref name="port"/> and <paramref name="secure"/>.
    /// </summary>
    /// <remarks>
    /// An instance initialized by this constructor listens for the incoming connection requests on
    /// <paramref name="port"/>.
    /// </remarks>
    /// <param name="port">
    /// An <see cref="int"/> that represents the port number on which to listen.
    /// </param>
    /// <param name="secure">
    /// A <see cref="bool"/> that indicates providing a secure connection or not.
    /// (<c>true</c> indicates providing a secure connection.)
    /// </param>
    /// <exception cref="ArgumentOutOfRangeException">
    /// <paramref name="port"/> isn't between 1 and 65535 inclusive.
    /// </exception>
    public WebSocketServer (int port, bool secure)
    {
      if (!port.IsPortNumber ())
        throw new ArgumentOutOfRangeException (
          "port", "Not between 1 and 65535 inclusive: " + port);

      init (null, System.Net.IPAddress.Any, port, secure);
    }

    /// <summary>
    /// Initializes a new instance of the <see cref="WebSocketServer"/> class with
    /// the specified <paramref name="address"/> and <paramref name="port"/>.
    /// </summary>
    /// <remarks>
    ///   <para>
    ///   An instance initialized by this constructor listens for the incoming connection requests
    ///   on <paramref name="address"/> and <paramref name="port"/>.
    ///   </para>
    ///   <para>
    ///   If <paramref name="port"/> is 443, that instance provides a secure connection.
    ///   </para>
    /// </remarks>
    /// <param name="address">
    /// A <see cref="System.Net.IPAddress"/> that represents the local IP address of the server.
    /// </param>
    /// <param name="port">
    /// An <see cref="int"/> that represents the port number on which to listen.
    /// </param>
    /// <exception cref="ArgumentNullException">
    /// <paramref name="address"/> is <see langword="null"/>.
    /// </exception>
    /// <exception cref="ArgumentException">
    /// <paramref name="address"/> isn't a local IP address.
    /// </exception>
    /// <exception cref="ArgumentOutOfRangeException">
    /// <paramref name="port"/> isn't between 1 and 65535 inclusive.
    /// </exception>
    public WebSocketServer (System.Net.IPAddress address, int port)
      : this (address, port, port == 443)
    {
    }

    /// <summary>
    /// Initializes a new instance of the <see cref="WebSocketServer"/> class with
    /// the specified <paramref name="address"/>, <paramref name="port"/>,
    /// and <paramref name="secure"/>.
    /// </summary>
    /// <remarks>
    /// An instance initialized by this constructor listens for the incoming connection requests on
    /// <paramref name="address"/> and <paramref name="port"/>.
    /// </remarks>
    /// <param name="address">
    /// A <see cref="System.Net.IPAddress"/> that represents the local IP address of the server.
    /// </param>
    /// <param name="port">
    /// An <see cref="int"/> that represents the port number on which to listen.
    /// </param>
    /// <param name="secure">
    /// A <see cref="bool"/> that indicates providing a secure connection or not.
    /// (<c>true</c> indicates providing a secure connection.)
    /// </param>
    /// <exception cref="ArgumentNullException">
    /// <paramref name="address"/> is <see langword="null"/>.
    /// </exception>
    /// <exception cref="ArgumentException">
    /// <paramref name="address"/> isn't a local IP address.
    /// </exception>
    /// <exception cref="ArgumentOutOfRangeException">
    /// <paramref name="port"/> isn't between 1 and 65535 inclusive.
    /// </exception>
    public WebSocketServer (System.Net.IPAddress address, int port, bool secure)
    {
      if (address == null)
        throw new ArgumentNullException ("address");

      if (!address.IsLocal ())
        throw new ArgumentException ("Not a local IP address: " + address, "address");

      if (!port.IsPortNumber ())
        throw new ArgumentOutOfRangeException (
          "port", "Not between 1 and 65535 inclusive: " + port);

      init (null, address, port, secure);
    }

    #endregion

    #region Public Properties

    /// <summary>
    /// Gets the local IP address of the server.
    /// </summary>
    /// <value>
    /// A <see cref="System.Net.IPAddress"/> that represents the local IP address of the server.
    /// </value>
    public System.Net.IPAddress Address {
      get {
        return _address;
      }
    }

    /// <summary>
    /// Gets or sets the scheme used to authenticate the clients.
    /// </summary>
    /// <value>
    /// One of the <see cref="WebSocketSharp.Net.AuthenticationSchemes"/> enum values,
    /// indicates the scheme used to authenticate the clients. The default value is
    /// <see cref="WebSocketSharp.Net.AuthenticationSchemes.Anonymous"/>.
    /// </value>
    public AuthenticationSchemes AuthenticationSchemes {
      get {
        return _authSchemes;
      }

      set {
        var msg = _state.CheckIfAvailable (true, false, false);
        if (msg != null) {
          _logger.Error (msg);
          return;
        }

        _authSchemes = value;
      }
    }

    /// <summary>
    /// Gets a value indicating whether the server has started.
    /// </summary>
    /// <value>
    /// <c>true</c> if the server has started; otherwise, <c>false</c>.
    /// </value>
    public bool IsListening {
      get {
        return _state == ServerState.Start;
      }
    }

    /// <summary>
    /// Gets a value indicating whether the server provides a secure connection.
    /// </summary>
    /// <value>
    /// <c>true</c> if the server provides a secure connection; otherwise, <c>false</c>.
    /// </value>
    public bool IsSecure {
      get {
        return _secure;
      }
    }

    /// <summary>
    /// Gets or sets a value indicating whether the server cleans up
    /// the inactive sessions periodically.
    /// </summary>
    /// <value>
    /// <c>true</c> if the server cleans up the inactive sessions every 60 seconds;
    /// otherwise, <c>false</c>. The default value is <c>true</c>.
    /// </value>
    public bool KeepClean {
      get {
        return _services.KeepClean;
      }

      set {
        var msg = _state.CheckIfAvailable (true, false, false);
        if (msg != null) {
          _logger.Error (msg);
          return;
        }

        _services.KeepClean = value;
      }
    }

    /// <summary>
    /// Gets the logging functions.
    /// </summary>
    /// <remarks>
    /// The default logging level is <see cref="LogLevel.Error"/>. If you would like to change it,
    /// you should set the <c>Log.Level</c> property to any of the <see cref="LogLevel"/> enum
    /// values.
    /// </remarks>
    /// <value>
    /// A <see cref="Logger"/> that provides the logging functions.
    /// </value>
    public Logger Log {
      get {
        return _logger;
      }
    }

    /// <summary>
    /// Gets the port on which to listen for incoming connection requests.
    /// </summary>
    /// <value>
    /// An <see cref="int"/> that represents the port number on which to listen.
    /// </value>
    public int Port {
      get {
        return _port;
      }
    }

    /// <summary>
    /// Gets or sets the name of the realm associated with the server.
    /// </summary>
    /// <remarks>
    /// If this property is <see langword="null"/> or empty, <c>"SECRET AREA"</c> will be used as
    /// the name of the realm.
    /// </remarks>
    /// <value>
    /// A <see cref="string"/> that represents the name of the realm. The default value is
    /// <see langword="null"/>.
    /// </value>
    public string Realm {
      get {
        return _realm;
      }

      set {
        var msg = _state.CheckIfAvailable (true, false, false);
        if (msg != null) {
          _logger.Error (msg);
          return;
        }

        _realm = value;
      }
    }

    /// <summary>
    /// Gets or sets a value indicating whether the server is allowed to be bound to
    /// an address that is already in use.
    /// </summary>
    /// <remarks>
    /// If you would like to resolve to wait for socket in <c>TIME_WAIT</c> state,
    /// you should set this property to <c>true</c>.
    /// </remarks>
    /// <value>
    /// <c>true</c> if the server is allowed to be bound to an address that is already in use;
    /// otherwise, <c>false</c>. The default value is <c>false</c>.
    /// </value>
    public bool ReuseAddress {
      get {
        return _reuseAddress;
      }

      set {
        var msg = _state.CheckIfAvailable (true, false, false);
        if (msg != null) {
          _logger.Error (msg);
          return;
        }

        _reuseAddress = value;
      }
    }

    /// <summary>
    /// Gets or sets the SSL configuration used to authenticate the server and
    /// optionally the client for secure connection.
    /// </summary>
    /// <value>
    /// A <see cref="ServerSslConfiguration"/> that represents the configuration used to
    /// authenticate the server and optionally the client for secure connection.
    /// </value>
    public ServerSslConfiguration SslConfiguration {
      get {
        return _sslConfig ?? (_sslConfig = new ServerSslConfiguration (null));
      }

      set {
        var msg = _state.CheckIfAvailable (true, false, false);
        if (msg != null) {
          _logger.Error (msg);
          return;
        }

        _sslConfig = value;
      }
    }

    /// <summary>
    /// Gets or sets the delegate called to find the credentials for an identity used to
    /// authenticate a client.
    /// </summary>
    /// <value>
    /// A <c>Func&lt;<see cref="IIdentity"/>, <see cref="NetworkCredential"/>&gt;</c> delegate
    /// that references the method(s) used to find the credentials. The default value is
    /// <see langword="null"/>.
    /// </value>
    public Func<IIdentity, NetworkCredential> UserCredentialsFinder {
      get {
        return _userCredFinder;
      }

      set {
        var msg = _state.CheckIfAvailable (true, false, false);
        if (msg != null) {
          _logger.Error (msg);
          return;
        }

        _userCredFinder = value;
      }
    }

    /// <summary>
    /// Gets or sets the wait time for the response to the WebSocket Ping or Close.
    /// </summary>
    /// <value>
    /// A <see cref="TimeSpan"/> that represents the wait time. The default value is
    /// the same as 1 second.
    /// </value>
    public TimeSpan WaitTime {
      get {
        return _services.WaitTime;
      }

      set {
        var msg = _state.CheckIfAvailable (true, false, false) ?? value.CheckIfValidWaitTime ();
        if (msg != null) {
          _logger.Error (msg);
          return;
        }

        _services.WaitTime = value;
      }
    }

    /// <summary>
    /// Gets the access to the WebSocket services provided by the server.
    /// </summary>
    /// <value>
    /// A <see cref="WebSocketServiceManager"/> that manages the WebSocket services.
    /// </value>
    public WebSocketServiceManager WebSocketServices {
      get {
        return _services;
      }
    }

    #endregion

    #region Private Methods

    private void abort ()
    {
      lock (_sync) {
        if (!IsListening)
          return;

        _state = ServerState.ShuttingDown;
      }

      _listener.Stop ();
      _services.Stop (new CloseEventArgs (CloseStatusCode.ServerError), true, false);

      _state = ServerState.Stop;
    }

    private bool checkIfAvailable (
      bool ready, bool start, bool shutting, bool stop, out string message
    )
    {
      message = null;

      if (!ready && _state == ServerState.Ready) {
        message = "This operation is not available in: ready";
        return false;
      }

      if (!start && _state == ServerState.Start) {
        message = "This operation is not available in: start";
        return false;
      }

      if (!shutting && _state == ServerState.ShuttingDown) {
        message = "This operation is not available in: shutting down";
        return false;
      }

      if (!stop && _state == ServerState.Stop) {
        message = "This operation is not available in: stop";
        return false;
      }

      return true;
    }

    private string checkIfCertificateExists ()
    {
      return _secure && (_sslConfig == null || _sslConfig.ServerCertificate == null)
             ? "The secure connection requires a server certificate."
             : null;
    }

    private string getRealm ()
    {
      var realm = _realm;
      return realm != null && realm.Length > 0 ? realm : _defaultRealm;
    }

    private void init (string hostname, System.Net.IPAddress address, int port, bool secure)
    {
      _hostname = hostname ?? address.ToString ();
      _address = address;
      _port = port;
      _secure = secure;

      _authSchemes = AuthenticationSchemes.Anonymous;
      _dnsStyle = Uri.CheckHostName (hostname) == UriHostNameType.Dns;
      _listener = new TcpListener (address, port);
      _logger = new Logger ();
      _services = new WebSocketServiceManager (_logger);
      _sync = new object ();
    }

    private void processRequest (TcpListenerWebSocketContext context)
    {
      var uri = context.RequestUri;
      if (uri == null || uri.Port != _port) {
        context.Close (HttpStatusCode.BadRequest);
        return;
      }

      if (_dnsStyle) {
        var hostname = uri.DnsSafeHost;
        if (Uri.CheckHostName (hostname) == UriHostNameType.Dns && hostname != _hostname) {
          context.Close (HttpStatusCode.NotFound);
          return;
        }
      }

      WebSocketServiceHost host;
      if (!_services.InternalTryGetServiceHost (uri.AbsolutePath, out host)) {
        context.Close (HttpStatusCode.NotImplemented);
        return;
      }

      host.StartSession (context);
    }

    private void receiveRequest ()
    {
      while (true) {
        try {
          var cl = _listener.AcceptTcpClient ();
          ThreadPool.QueueUserWorkItem (
            state => {
              try {
                var ctx = cl.GetWebSocketContext (null, _secure, _sslConfig, _logger);
                if (!ctx.Authenticate (_authSchemes, getRealm (), _userCredFinder))
                  return;

                processRequest (ctx);
              }
              catch (Exception ex) {
                _logger.Fatal (ex.ToString ());
                cl.Close ();
              }
            }
          );
        }
        catch (SocketException ex) {
          _logger.Warn ("Receiving has been stopped.\n  reason: " + ex.Message);
          break;
        }
        catch (Exception ex) {
          _logger.Fatal (ex.ToString ());
          break;
        }
      }

      if (IsListening)
        abort ();
    }

    private void startReceiving ()
    {
      if (_reuseAddress)
        _listener.Server.SetSocketOption (
          SocketOptionLevel.Socket, SocketOptionName.ReuseAddress, true);

      _listener.Start ();
      _receiveThread = new Thread (new ThreadStart (receiveRequest));
      _receiveThread.IsBackground = true;
      _receiveThread.Start ();
    }

    private void stopReceiving (int millisecondsTimeout)
    {
      _listener.Stop ();
      _receiveThread.Join (millisecondsTimeout);
    }

    private static bool tryCreateUri (string uriString, out Uri result, out string message)
    {
      if (!uriString.TryCreateWebSocketUri (out result, out message))
        return false;

      if (result.PathAndQuery != "/") {
        result = null;
        message = "Includes the path or query component: " + uriString;

        return false;
      }

      return true;
    }

    #endregion

    #region Public Methods

    /// <summary>
    /// Adds a WebSocket service with the specified behavior, <paramref name="path"/>,
    /// and <paramref name="initializer"/>.
    /// </summary>
    /// <remarks>
    ///   <para>
    ///   This method converts <paramref name="path"/> to URL-decoded string,
    ///   and removes <c>'/'</c> from tail end of <paramref name="path"/>.
    ///   </para>
    ///   <para>
    ///   <paramref name="initializer"/> returns an initialized specified typed
    ///   <see cref="WebSocketBehavior"/> instance.
    ///   </para>
    /// </remarks>
    /// <param name="path">
    /// A <see cref="string"/> that represents the absolute path to the service to add.
    /// </param>
    /// <param name="initializer">
    /// A <c>Func&lt;T&gt;</c> delegate that references the method used to initialize
    /// a new specified typed <see cref="WebSocketBehavior"/> instance (a new
    /// <see cref="IWebSocketSession"/> instance).
    /// </param>
    /// <typeparam name="TBehavior">
    /// The type of the behavior of the service to add. The TBehavior must inherit
    /// the <see cref="WebSocketBehavior"/> class.
    /// </typeparam>
    public void AddWebSocketService<TBehavior> (string path, Func<TBehavior> initializer)
      where TBehavior : WebSocketBehavior
    {
      var msg = path.CheckIfValidServicePath () ??
                (initializer == null ? "'initializer' is null." : null);

      if (msg != null) {
        _logger.Error (msg);
        return;
      }

      _services.Add<TBehavior> (path, initializer);
    }

    /// <summary>
    /// Adds a WebSocket service with the specified behavior and <paramref name="path"/>.
    /// </summary>
    /// <remarks>
    /// This method converts <paramref name="path"/> to URL-decoded string,
    /// and removes <c>'/'</c> from tail end of <paramref name="path"/>.
    /// </remarks>
    /// <param name="path">
    /// A <see cref="string"/> that represents the absolute path to the service to add.
    /// </param>
    /// <typeparam name="TBehaviorWithNew">
    /// The type of the behavior of the service to add. The TBehaviorWithNew must inherit
    /// the <see cref="WebSocketBehavior"/> class, and must have a public parameterless
    /// constructor.
    /// </typeparam>
    public void AddWebSocketService<TBehaviorWithNew> (string path)
      where TBehaviorWithNew : WebSocketBehavior, new ()
    {
      AddWebSocketService<TBehaviorWithNew> (path, () => new TBehaviorWithNew ());
    }

    /// <summary>
    /// Removes the WebSocket service with the specified <paramref name="path"/>.
    /// </summary>
    /// <remarks>
    /// This method converts <paramref name="path"/> to URL-decoded string,
    /// and removes <c>'/'</c> from tail end of <paramref name="path"/>.
    /// </remarks>
    /// <returns>
    /// <c>true</c> if the service is successfully found and removed; otherwise, <c>false</c>.
    /// </returns>
    /// <param name="path">
    /// A <see cref="string"/> that represents the absolute path to the service to find.
    /// </param>
    public bool RemoveWebSocketService (string path)
    {
      var msg = path.CheckIfValidServicePath ();
      if (msg != null) {
        _logger.Error (msg);
        return false;
      }

      return _services.Remove (path);
    }

    /// <summary>
    /// Starts receiving the WebSocket connection requests.
    /// </summary>
    public void Start ()
    {
      lock (_sync) {
        var msg = _state.CheckIfAvailable (true, false, false) ?? checkIfCertificateExists ();
        if (msg != null) {
          _logger.Error (msg);
          return;
        }

        _services.Start ();
        startReceiving ();

        _state = ServerState.Start;
      }
    }

    /// <summary>
    /// Stops receiving the WebSocket handshake requests, and closes
    /// the WebSocket connections.
    /// </summary>
    public void Stop ()
    {
      string msg;
      if (!checkIfAvailable (false, true, false, false, out msg)) {
        _logger.Error (msg);
        return;
      }

      lock (_sync) {
        if (!checkIfAvailable (false, true, false, false, out msg)) {
          _logger.Error (msg);
          return;
        }

        _state = ServerState.ShuttingDown;
      }

      stopReceiving (5000);
      _services.Stop (new CloseEventArgs (), true, true);

      _state = ServerState.Stop;
    }

    /// <summary>
    /// Stops receiving the WebSocket handshake requests, and closes
    /// the WebSocket connections with the specified <paramref name="code"/> and
    /// <paramref name="reason"/>.
    /// </summary>
    /// <param name="code">
    /// A <see cref="ushort"/> that represents the status code indicating
    /// the reason for the close. The status codes are defined in
    /// <see href="http://tools.ietf.org/html/rfc6455#section-7.4">
    /// Section 7.4</see> of RFC 6455.
    /// </param>
    /// <param name="reason">
    /// A <see cref="string"/> that represents the reason for the close.
    /// The size must be 123 bytes or less.
    /// </param>
    public void Stop (ushort code, string reason)
    {
      string msg;
      if (!checkIfAvailable (false, true, false, false, out msg)) {
        _logger.Error (msg);
        return;
      }

      if (!WebSocket.CheckParametersForClose (code, reason, false, out msg)) {
        _logger.Error (msg);
        return;
      }

      lock (_sync) {
        if (!checkIfAvailable (false, true, false, false, out msg)) {
          _logger.Error (msg);
          return;
        }

        _state = ServerState.ShuttingDown;
      }

      stopReceiving (5000);

      if (code == (ushort) CloseStatusCode.NoStatus) {
        _services.Stop (new CloseEventArgs (), true, true);
      }
      else {
        var send = !code.IsReserved ();
        _services.Stop (new CloseEventArgs (code, reason), send, send);
      }

      _state = ServerState.Stop;
    }

    /// <summary>
    /// Stops receiving the WebSocket connection requests with
    /// the specified <see cref="CloseStatusCode"/> and <see cref="string"/>.
    /// </summary>
    /// <param name="code">
    /// One of the <see cref="CloseStatusCode"/> enum values, represents the status code indicating
    /// the reason for the stop.
    /// </param>
    /// <param name="reason">
    /// A <see cref="string"/> that represents the reason for the stop.
    /// </param>
    public void Stop (CloseStatusCode code, string reason)
    {
      string msg;
      if (!checkIfAvailable (false, true, false, false, out msg)) {
        _logger.Error (msg);
        return;
      }

      if (!WebSocket.CheckParametersForClose (code, reason, false, out msg)) {
        _logger.Error (msg);
        return;
      }

      lock (_sync) {
        if (!checkIfAvailable (false, true, false, false, out msg)) {
          _logger.Error (msg);
          return;
        }

        _state = ServerState.ShuttingDown;
      }

      stopReceiving (5000);

      if (code == CloseStatusCode.NoStatus) {
        _services.Stop (new CloseEventArgs (), true, true);
      }
      else {
        var send = !code.IsReserved ();
        _services.Stop (new CloseEventArgs (code, reason), send, send);
      }

      _state = ServerState.Stop;
    }

    #endregion
  }
}