diff --git a/websocket-sharp/Ext.cs b/websocket-sharp/Ext.cs
index 146e0e0f..484eb117 100644
--- a/websocket-sharp/Ext.cs
+++ b/websocket-sharp/Ext.cs
@@ -817,6 +817,11 @@ namespace WebSocketSharp
       }
     }
 
+    internal static List<TSource> ToList<TSource> (this IEnumerable<TSource> source)
+    {
+      return new List<TSource> (source);
+    }
+
     internal static ushort ToUInt16 (this byte [] src, ByteOrder srcOrder)
     {
       return BitConverter.ToUInt16 (src.ToHostOrder (srcOrder), 0);
diff --git a/websocket-sharp/Server/WebSocketServiceManager.cs b/websocket-sharp/Server/WebSocketServiceManager.cs
index dd35de22..072cccd6 100644
--- a/websocket-sharp/Server/WebSocketServiceManager.cs
+++ b/websocket-sharp/Server/WebSocketServiceManager.cs
@@ -87,24 +87,26 @@ namespace WebSocketSharp.Server
     }
 
     /// <summary>
-    /// Gets the collection of the WebSocket service hosts.
+    /// Gets the collection of every information in the Websocket services provided by the server.
     /// </summary>
     /// <value>
-    /// An IEnumerable&lt;WebSocketServiceHost&gt; that contains the collection of the WebSocket
-    /// service hosts.
+    /// An IEnumerable&lt;WebSocketServiceHost&gt; that contains the collection of every
+    /// information in the Websocket services.
     /// </value>
     public IEnumerable<WebSocketServiceHost> Hosts {
       get {
-        return copyHosts ().Values;
+        lock (_sync) {
+          return _hosts.Values.ToList ();
+        }
       }
     }
 
     /// <summary>
-    /// Gets a WebSocket service host with the specified <paramref name="path"/>.
+    /// Gets the information in a WebSocket service with the specified <paramref name="path"/>.
     /// </summary>
     /// <value>
-    /// A <see cref="WebSocketServiceHost"/> instance that represents the WebSocket service host if
-    /// it's successfully found; otherwise, <see langword="null"/>.
+    /// A <see cref="WebSocketServiceHost"/> instance that provides the access to the WebSocket
+    /// service if it's successfully found; otherwise, <see langword="null"/>.
     /// </value>
     /// <param name="path">
     /// A <see cref="string"/> that represents the absolute path to the WebSocket service to find.
@@ -152,7 +154,9 @@ namespace WebSocketSharp.Server
     /// </value>
     public IEnumerable<string> Paths {
       get {
-        return copyHosts ().Keys;
+        lock (_sync) {
+          return _hosts.Keys.ToList ();
+        }
       }
     }
 
@@ -253,13 +257,6 @@ namespace WebSocketSharp.Server
       return result;
     }
 
-    private Dictionary<string, WebSocketServiceHost> copyHosts ()
-    {
-      lock (_sync) {
-        return new Dictionary<string, WebSocketServiceHost> (_hosts);
-      }
-    }
-
     #endregion
 
     #region Internal Methods
@@ -328,7 +325,6 @@ namespace WebSocketSharp.Server
           host.Sessions.Stop (args, frameAsBytes);
 
         _hosts.Clear ();
-
         _state = ServerState.STOP;
       }
     }
@@ -555,7 +551,8 @@ namespace WebSocketSharp.Server
     }
 
     /// <summary>
-    /// Tries to get a WebSocket service host with the specified <paramref name="path"/>.
+    /// Tries to get the information in a WebSocket service with the specified
+    /// <paramref name="path"/>.
     /// </summary>
     /// <returns>
     /// <c>true</c> if the WebSocket service is successfully found; otherwise, <c>false</c>.
@@ -564,9 +561,9 @@ namespace WebSocketSharp.Server
     /// A <see cref="string"/> that represents the absolute path to the WebSocket service to find.
     /// </param>
     /// <param name="host">
-    /// When this method returns, a <see cref="WebSocketServiceHost"/> instance that represents the
-    /// WebSocket service host if it's successfully found; otherwise, <see langword="null"/>. This
-    /// parameter is passed uninitialized.
+    /// When this method returns, a <see cref="WebSocketServiceHost"/> instance that
+    /// provides the access to the WebSocket service if it's successfully found;
+    /// otherwise, <see langword="null"/>. This parameter is passed uninitialized.
     /// </param>
     public bool TryGetServiceHost (string path, out WebSocketServiceHost host)
     {
diff --git a/websocket-sharp/Server/WebSocketSessionManager.cs b/websocket-sharp/Server/WebSocketSessionManager.cs
index 066d3a60..d0f7811d 100644
--- a/websocket-sharp/Server/WebSocketSessionManager.cs
+++ b/websocket-sharp/Server/WebSocketSessionManager.cs
@@ -42,7 +42,7 @@ namespace WebSocketSharp.Server
   {
     #region Private Static Fields
 
-    private static readonly List<IWebSocketSession> _emptySessions;
+    private static readonly Dictionary<string, IWebSocketSession> _emptySessions;
 
     #endregion
 
@@ -63,7 +63,7 @@ namespace WebSocketSharp.Server
 
     static WebSocketSessionManager ()
     {
-      _emptySessions = new List<IWebSocketSession> ();
+      _emptySessions = new Dictionary<string, IWebSocketSession> ();
     }
 
     #endregion
@@ -138,7 +138,12 @@ namespace WebSocketSharp.Server
     /// </value>
     public IEnumerable<string> IDs {
       get {
-        return copySessions ().Keys;
+        if (_state == ServerState.SHUTDOWN)
+          return _emptySessions.Keys;
+
+        lock (_sync) {
+          return _sessions.Keys.ToList ();
+        }
       }
     }
 
@@ -158,11 +163,11 @@ namespace WebSocketSharp.Server
     }
 
     /// <summary>
-    /// Gets a session information with the specified <paramref name="id"/> in the WebSocket
+    /// Gets the information in a session with the specified <paramref name="id"/> in the WebSocket
     /// service.
     /// </summary>
     /// <value>
-    /// A <see cref="IWebSocketSession"/> instance that represents the session information if it's
+    /// A <see cref="IWebSocketSession"/> instance that provides the access to the session if it's
     /// successfully found; otherwise, <see langword="null"/>.
     /// </value>
     /// <param name="id">
@@ -200,18 +205,20 @@ namespace WebSocketSharp.Server
     }
 
     /// <summary>
-    /// Gets the collection of the session informations in the Websocket service.
+    /// Gets the collection of every information in the sessions in the Websocket service.
     /// </summary>
     /// <value>
-    /// An IEnumerable&lt;IWebSocketSession&gt; that contains the collection of the session
-    /// informations.
+    /// An IEnumerable&lt;IWebSocketSession&gt; that contains the collection of every information
+    /// in the sessions.
     /// </value>
     public IEnumerable<IWebSocketSession> Sessions {
       get {
         if (_state == ServerState.SHUTDOWN)
-          return _emptySessions;
+          return _emptySessions.Values;
 
-        return copySessions ().Values;
+        lock (_sync) {
+          return _sessions.Values.ToList ();
+        }
       }
     }
 
@@ -266,13 +273,6 @@ namespace WebSocketSharp.Server
         state => broadcast (opcode, stream, completed));
     }
 
-    private Dictionary<string, IWebSocketSession> copySessions ()
-    {
-      lock (_sync) {
-        return new Dictionary<string, IWebSocketSession> (_sessions);
-      }
-    }
-
     private static string createID ()
     {
       return Guid.NewGuid ().ToString ("N");
@@ -380,7 +380,7 @@ namespace WebSocketSharp.Server
         _state = ServerState.SHUTDOWN;
 
         _sweepTimer.Enabled = false;
-        foreach (var session in copySessions ().Values)
+        foreach (var session in _sessions.Values.ToList ())
           session.Context.WebSocket.Close (args, frame, 1000);
 
         _state = ServerState.STOP;
@@ -609,7 +609,7 @@ namespace WebSocketSharp.Server
     /// A <see cref="string"/> that represents the ID of the session to close.
     /// </param>
     /// <param name="code">
-    /// A <see cref="ushort"/> that indicates the status code for closure.
+    /// A <see cref="ushort"/> that represents the status code indicating the reason for closure.
     /// </param>
     /// <param name="reason">
     /// A <see cref="string"/> that represents the reason for closure.
@@ -629,8 +629,8 @@ namespace WebSocketSharp.Server
     /// A <see cref="string"/> that represents the ID of the session to close.
     /// </param>
     /// <param name="code">
-    /// One of the <see cref="CloseStatusCode"/> enum values, indicates the status code for
-    /// closure.
+    /// One of the <see cref="CloseStatusCode"/> enum values, represents the status code indicating
+    /// the reason for closure.
     /// </param>
     /// <param name="reason">
     /// A <see cref="string"/> that represents the reason for closure.
@@ -826,7 +826,7 @@ namespace WebSocketSharp.Server
     }
 
     /// <summary>
-    /// Tries to get a session information with the specified <paramref name="id"/> in the
+    /// Tries to get the information in a session with the specified <paramref name="id"/> in the
     /// WebSocket service.
     /// </summary>
     /// <returns>
@@ -836,8 +836,8 @@ namespace WebSocketSharp.Server
     /// A <see cref="string"/> that represents the ID of the session to find.
     /// </param>
     /// <param name="session">
-    /// When this method returns, a <see cref="IWebSocketSession"/> instance that represents the
-    /// session information if it's successfully found; otherwise, <see langword="null"/>. This
+    /// When this method returns, a <see cref="IWebSocketSession"/> instance that provides the
+    /// access to the session if it's successfully found; otherwise, <see langword="null"/>. This
     /// parameter is passed uninitialized.
     /// </param>
     public bool TryGetSession (string id, out IWebSocketSession session)