diff --git a/websocket-sharp/Server/HttpServer.cs b/websocket-sharp/Server/HttpServer.cs
index a3d8f651..dce9a5e7 100644
--- a/websocket-sharp/Server/HttpServer.cs
+++ b/websocket-sharp/Server/HttpServer.cs
@@ -387,7 +387,7 @@ namespace WebSocketSharp.Server
       var wsContext = context.AcceptWebSocket ();
       var path = wsContext.Path.UrlDecode ();
 
-      IServiceHost host;
+      IWebSocketServiceHost host;
       if (!_serviceHosts.TryGetServiceHost (path, out host))
       {
         context.Response.StatusCode = (int) HttpStatusCode.NotImplemented;
diff --git a/websocket-sharp/Server/IServiceHost.cs b/websocket-sharp/Server/IWebSocketServiceHost.cs
similarity index 87%
rename from websocket-sharp/Server/IServiceHost.cs
rename to websocket-sharp/Server/IWebSocketServiceHost.cs
index 5fec48b9..d7c1c00a 100644
--- a/websocket-sharp/Server/IServiceHost.cs
+++ b/websocket-sharp/Server/IWebSocketServiceHost.cs
@@ -1,6 +1,6 @@
 #region License
 /*
- * IServiceHost.cs
+ * IWebSocketServiceHost.cs
  *
  * The MIT License
  *
@@ -35,9 +35,7 @@ namespace WebSocketSharp.Server
   /// <summary>
   /// Exposes the methods and properties for the WebSocket service host.
   /// </summary>
-  /// <remarks>
-  /// </remarks>
-  public interface IServiceHost
+  public interface IWebSocketServiceHost
   {
     /// <summary>
     /// Gets the connection count to the WebSocket service host.
@@ -82,11 +80,12 @@ namespace WebSocketSharp.Server
     void Broadcast (string data);
 
     /// <summary>
-    /// Sends Pings with the specified <see cref="string"/> to all clients of the WebSocket service host.
+    /// Sends Pings with the specified <paramref name="message"/> to all clients of
+    /// the WebSocket service host.
     /// </summary>
     /// <returns>
-    /// A Dictionary&lt;string, bool&gt; that contains the collection of session IDs and values
-    /// indicating whether the WebSocket service host received the Pongs from each clients in a time.
+    /// A Dictionary&lt;string, bool&gt; that contains the collection of pairs of session ID and value
+    /// indicating whether the WebSocket service host received the Pong from each client in a time.
     /// </returns>
     /// <param name="message">
     /// A <see cref="string"/> that contains a message to send.
@@ -94,50 +93,48 @@ namespace WebSocketSharp.Server
     Dictionary<string, bool> Broadping (string message);
 
     /// <summary>
-    /// Sends a Ping with the specified <see cref="string"/> to the client associated with
+    /// Sends a Ping with the specified <paramref name="message"/> to the client associated with
     /// the specified ID.
     /// </summary>
     /// <returns>
     /// <c>true</c> if the WebSocket service host receives a Pong from the client in a time;
     /// otherwise, <c>false</c>.
     /// </returns>
-    /// <param name="id">
-    /// A <see cref="string"/> that contains an ID that represents the destination for the Ping.
-    /// </param>
     /// <param name="message">
     /// A <see cref="string"/> that contains a message to send.
     /// </param>
-    bool PingTo (string id, string message);
+    /// <param name="id">
+    /// A <see cref="string"/> that contains an ID that represents the destination for the Ping.
+    /// </param>
+    bool PingTo (string message, string id);
 
     /// <summary>
     /// Sends a binary data to the client associated with the specified ID.
     /// </summary>
     /// <returns>
-    /// <c>true</c> if the client associated with <paramref name="id"/> is successfully found;
-    /// otherwise, <c>false</c>.
+    /// <c>true</c> if <paramref name="data"/> is successfully sent; otherwise, <c>false</c>.
     /// </returns>
-    /// <param name="id">
-    /// A <see cref="string"/> that contains an ID that represents the destination for the data.
-    /// </param>
     /// <param name="data">
     /// An array of <see cref="byte"/> that contains a binary data to send.
     /// </param>
-    bool SendTo (string id, byte [] data);
+    /// <param name="id">
+    /// A <see cref="string"/> that contains an ID that represents the destination for the data.
+    /// </param>
+    bool SendTo (byte [] data, string id);
 
     /// <summary>
     /// Sends a text data to the client associated with the specified ID.
     /// </summary>
     /// <returns>
-    /// <c>true</c> if the client associated with <paramref name="id"/> is successfully found;
-    /// otherwise, <c>false</c>.
+    /// <c>true</c> if <paramref name="data"/> is successfully sent; otherwise, <c>false</c>.
     /// </returns>
-    /// <param name="id">
-    /// A <see cref="string"/> that contains an ID that represents the destination for the data.
-    /// </param>
     /// <param name="data">
     /// A <see cref="string"/> that contains a text data to send.
     /// </param>
-    bool SendTo (string id, string data);
+    /// <param name="id">
+    /// A <see cref="string"/> that contains an ID that represents the destination for the data.
+    /// </param>
+    bool SendTo (string data, string id);
 
     /// <summary>
     /// Starts the WebSocket service host.
diff --git a/websocket-sharp/Server/WebSocketServer.cs b/websocket-sharp/Server/WebSocketServer.cs
index 1677b7f7..f0e9d91f 100644
--- a/websocket-sharp/Server/WebSocketServer.cs
+++ b/websocket-sharp/Server/WebSocketServer.cs
@@ -226,7 +226,7 @@ namespace WebSocketSharp.Server
       var path = context.Path.UrlDecode ();
 
       websocket.Log = Log;
-      IServiceHost host;
+      IWebSocketServiceHost host;
       if (!_serviceHosts.TryGetServiceHost (path, out host))
       {
         websocket.Close (HttpStatusCode.NotImplemented);
diff --git a/websocket-sharp/Server/WebSocketService.cs b/websocket-sharp/Server/WebSocketService.cs
index 730ecf27..cd48680f 100644
--- a/websocket-sharp/Server/WebSocketService.cs
+++ b/websocket-sharp/Server/WebSocketService.cs
@@ -349,8 +349,8 @@ namespace WebSocketSharp.Server
     /// in the <see cref="WebSocketService.Sessions"/>.
     /// </summary>
     /// <returns>
-    /// A Dictionary&lt;string, bool&gt; that contains the collection of IDs and values indicating
-    /// whether the each <see cref="WebSocketService"/> instances received a Pong in a time.
+    /// A Dictionary&lt;string, bool&gt; that contains the collection of pairs of session ID and value
+    /// indicating whether the each <see cref="WebSocketService"/> instance received a Pong in a time.
     /// </returns>
     public virtual Dictionary<string, bool> Broadping ()
     {
@@ -360,12 +360,12 @@ namespace WebSocketSharp.Server
     }
 
     /// <summary>
-    /// Sends Pings with the specified <see cref="string"/> to the clients of every <see cref="WebSocketService"/>
+    /// Sends Pings with the specified <paramref name="message"/> to the clients of every <see cref="WebSocketService"/>
     /// instances in the <see cref="WebSocketService.Sessions"/>.
     /// </summary>
     /// <returns>
-    /// A Dictionary&lt;string, bool&gt; that contains the collection of IDs and values
-    /// indicating whether the each <see cref="WebSocketService"/> instances received a Pong in a time.
+    /// A Dictionary&lt;string, bool&gt; that contains the collection of pairs of session ID and value
+    /// indicating whether the each <see cref="WebSocketService"/> instance received a Pong in a time.
     /// </returns>
     /// <param name="message">
     /// A <see cref="string"/> that contains a message to send.
@@ -406,7 +406,7 @@ namespace WebSocketSharp.Server
     }
 
     /// <summary>
-    /// Sends a Ping with the specified <see cref="string"/> to the client of
+    /// Sends a Ping with the specified <paramref name="message"/> to the client of
     /// the current <see cref="WebSocketService"/> instance.
     /// </summary>
     /// <returns>
@@ -428,54 +428,46 @@ namespace WebSocketSharp.Server
     /// with the specified ID.
     /// </summary>
     /// <returns>
-    /// <c>true</c> if the <see cref="WebSocketService"/> instance receives a Pong in a time;
-    /// otherwise, <c>false</c>.
+    /// <c>true</c> if the <see cref="WebSocketService"/> instance with <paramref name="id"/> receives
+    /// a Pong in a time; otherwise, <c>false</c>.
     /// </returns>
     /// <param name="id">
     /// A <see cref="string"/> that contains an ID that represents the destination for the Ping.
     /// </param>
     public virtual bool PingTo (string id)
     {
-      return PingTo (id, String.Empty);
+      return PingTo (String.Empty, id);
     }
 
     /// <summary>
-    /// Sends a Ping with the specified <see cref="string"/> to the client of the <see cref="WebSocketService"/>
-    /// instance with the specified ID.
+    /// Sends a Ping with the specified <paramref name="message"/> to the client of
+    /// the <see cref="WebSocketService"/> instance with the specified ID.
     /// </summary>
     /// <returns>
-    /// <c>true</c> if the <see cref="WebSocketService"/> instance receives a Pong in a time;
-    /// otherwise, <c>false</c>.
+    /// <c>true</c> if the <see cref="WebSocketService"/> instance with <paramref name="id"/> receives
+    /// a Pong in a time; otherwise, <c>false</c>.
     /// </returns>
-    /// <param name="id">
-    /// A <see cref="string"/> that contains an ID that represents the destination for the Ping.
-    /// </param>
     /// <param name="message">
     /// A <see cref="string"/> that contains a message to send.
     /// </param>
-    public virtual bool PingTo (string id, string message)
+    /// <param name="id">
+    /// A <see cref="string"/> that contains an ID that represents the destination for the Ping.
+    /// </param>
+    public virtual bool PingTo (string message, string id)
     {
       if (!IsBound)
         return false;
 
-      if (message == null)
-        message = String.Empty;
-
-      var msg = id.IsNullOrEmpty ()
-              ? "'id' must not be null or empty."
-              : Encoding.UTF8.GetBytes (message).Length > 125
-                ? "The payload length of a Ping frame must be 125 bytes or less."
-                : String.Empty;
-
-      if (msg.Length > 0)
+      if (id.IsNullOrEmpty ())
       {
+        var msg = "'id' must not be null or empty.";
         Log.Error (msg);
         Error (msg);
 
         return false;
       }
 
-      return _sessions.PingTo (id, message);
+      return _sessions.PingTo (message, id);
     }
 
     /// <summary>
@@ -507,26 +499,26 @@ namespace WebSocketSharp.Server
     /// with the specified ID.
     /// </summary>
     /// <returns>
-    /// <c>true</c> if the client is successfully found; otherwise, <c>false</c>.
+    /// <c>true</c> if <paramref name="data"/> is successfully sent; otherwise, <c>false</c>.
     /// </returns>
-    /// <param name="id">
-    /// A <see cref="string"/> that contains an ID that represents the destination for the data.
-    /// </param>
     /// <param name="data">
     /// An array of <see cref="byte"/> that contains a binary data to send.
     /// </param>
-    public virtual bool SendTo (string id, byte [] data)
+    /// <param name="id">
+    /// A <see cref="string"/> that contains an ID that represents the destination for the data.
+    /// </param>
+    public virtual bool SendTo (byte [] data, string id)
     {
       if (!IsBound)
         return false;
 
-      var msg = id.IsNullOrEmpty ()
-              ? "'id' must not be null or empty."
-              : data == null
-                ? "'data' must not be null."
-                : String.Empty;
+      var msg = data == null
+              ? "'data' must not be null."
+              : id.IsNullOrEmpty ()
+                ? "'id' must not be null or empty."
+                : null;
 
-      if (msg.Length > 0)
+      if (msg != null)
       {
         Log.Error (msg);
         Error (msg);
@@ -534,7 +526,7 @@ namespace WebSocketSharp.Server
         return false;
       }
 
-      return _sessions.SendTo (id, data);
+      return _sessions.SendTo (data, id);
     }
 
     /// <summary>
@@ -542,26 +534,26 @@ namespace WebSocketSharp.Server
     /// with the specified ID.
     /// </summary>
     /// <returns>
-    /// <c>true</c> if the client is successfully found; otherwise, <c>false</c>.
+    /// <c>true</c> if <paramref name="data"/> is successfully sent; otherwise, <c>false</c>.
     /// </returns>
-    /// <param name="id">
-    /// A <see cref="string"/> that contains an ID that represents the destination for the data.
-    /// </param>
     /// <param name="data">
     /// A <see cref="string"/> that contains a text data to send.
     /// </param>
-    public virtual bool SendTo (string id, string data)
+    /// <param name="id">
+    /// A <see cref="string"/> that contains an ID that represents the destination for the data.
+    /// </param>
+    public virtual bool SendTo (string data, string id)
     {
       if (!IsBound)
         return false;
 
-      var msg = id.IsNullOrEmpty ()
-              ? "'id' must not be null or empty."
-              : data == null
-                ? "'data' must not be null."
-                : String.Empty;
+      var msg = data == null
+              ? "'data' must not be null."
+              : id.IsNullOrEmpty ()
+                ? "'id' must not be null or empty."
+                : null;
 
-      if (msg.Length > 0)
+      if (msg != null)
       {
         Log.Error (msg);
         Error (msg);
@@ -569,11 +561,11 @@ namespace WebSocketSharp.Server
         return false;
       }
 
-      return _sessions.SendTo (id, data);
+      return _sessions.SendTo (data, id);
     }
 
     /// <summary>
-    /// Starts a <see cref="WebSocketService"/> instance.
+    /// Starts the current <see cref="WebSocketService"/> instance.
     /// </summary>
     public void Start ()
     {
diff --git a/websocket-sharp/Server/WebSocketServiceHost.cs b/websocket-sharp/Server/WebSocketServiceHost.cs
index 3409255e..8c293fe1 100644
--- a/websocket-sharp/Server/WebSocketServiceHost.cs
+++ b/websocket-sharp/Server/WebSocketServiceHost.cs
@@ -47,7 +47,7 @@ namespace WebSocketSharp.Server
   /// The type of the WebSocket service that the server provides.
   /// The T must inherit the <see cref="WebSocketService"/> class.
   /// </typeparam>
-  public class WebSocketServiceHost<T> : WebSocketServerBase, IServiceHost
+  public class WebSocketServiceHost<T> : WebSocketServerBase, IWebSocketServiceHost
     where T : WebSocketService, new ()
   {
     #region Private Fields
@@ -267,20 +267,20 @@ namespace WebSocketSharp.Server
     /// </param>
     protected override void AcceptWebSocket (TcpListenerWebSocketContext context)
     {
-      var ws = context.WebSocket;
+      var websocket = context.WebSocket;
       var path = context.Path.UrlDecode ();
 
-      ws.Log = Log;
+      websocket.Log = Log;
       if (path != Uri.GetAbsolutePath ().UrlDecode ())
       {
-        ws.Close (HttpStatusCode.NotImplemented);
+        websocket.Close (HttpStatusCode.NotImplemented);
         return;
       }
 
       if (Uri.IsAbsoluteUri)
-        ws.Url = Uri;
+        websocket.Url = Uri;
 
-      ((IServiceHost) this).BindWebSocket (context);
+      ((IWebSocketServiceHost) this).BindWebSocket (context);
     }
 
     #endregion
@@ -322,11 +322,11 @@ namespace WebSocketSharp.Server
     }
 
     /// <summary>
-    /// Sends Pings with the specified <see cref="string"/> to all clients.
+    /// Sends Pings with the specified <paramref name="message"/> to all clients.
     /// </summary>
     /// <returns>
-    /// A Dictionary&lt;string, bool&gt; that contains the collection of session IDs and values
-    /// indicating whether the service host received the Pongs from each clients in a time.
+    /// A Dictionary&lt;string, bool&gt; that contains the collection of pairs of session ID and value
+    /// indicating whether the service host received the Pong from each client in a time.
     /// </returns>
     /// <param name="message">
     /// A <see cref="string"/> that contains a message to send.
@@ -347,58 +347,48 @@ namespace WebSocketSharp.Server
     }
 
     /// <summary>
-    /// Sends a Ping with the specified <see cref="string"/> to the client associated with
+    /// Sends a Ping with the specified <paramref name="message"/> to the client associated with
     /// the specified ID.
     /// </summary>
     /// <returns>
     /// <c>true</c> if the service host receives a Pong from the client in a time; otherwise, <c>false</c>.
     /// </returns>
-    /// <param name="id">
-    /// A <see cref="string"/> that contains an ID that represents the destination for the Ping.
-    /// </param>
     /// <param name="message">
     /// A <see cref="string"/> that contains a message to send.
     /// </param>
-    public bool PingTo (string id, string message)
+    /// <param name="id">
+    /// A <see cref="string"/> that contains an ID that represents the destination for the Ping.
+    /// </param>
+    public bool PingTo (string message, string id)
     {
-      if (message == null)
-        message = String.Empty;
-
-      var msg = id.IsNullOrEmpty ()
-                ? "'id' must not be null or empty."
-                : Encoding.UTF8.GetBytes (message).Length > 125
-                  ? "The payload length of a Ping frame must be 125 bytes or less."
-                  : null;
-
-      if (msg != null)
+      if (id.IsNullOrEmpty ())
       {
-        Log.Error (msg);
+        Log.Error ("'id' must not be null or empty.");
         return false;
       }
 
-      return _sessions.PingTo (id, message);
+      return _sessions.PingTo (message, id);
     }
 
     /// <summary>
     /// Sends a binary data to the client associated with the specified ID.
     /// </summary>
     /// <returns>
-    /// <c>true</c> if the client associated with <paramref name="id"/> is successfully found;
-    /// otherwise, <c>false</c>.
+    /// <c>true</c> if <paramref name="data"/> is successfully sent; otherwise, <c>false</c>.
     /// </returns>
-    /// <param name="id">
-    /// A <see cref="string"/> that contains an ID that represents the destination for the data.
-    /// </param>
     /// <param name="data">
     /// An array of <see cref="byte"/> that contains a binary data to send.
     /// </param>
-    public bool SendTo (string id, byte [] data)
+    /// <param name="id">
+    /// A <see cref="string"/> that contains an ID that represents the destination for the data.
+    /// </param>
+    public bool SendTo (byte [] data, string id)
     {
-      var msg = id.IsNullOrEmpty ()
+      var msg = data == null
+              ? "'data' must not be null."
+              : id.IsNullOrEmpty ()
                 ? "'id' must not be null or empty."
-                : data == null
-                  ? "'data' must not be null."
-                  : null;
+                : null;
 
       if (msg != null)
       {
@@ -406,29 +396,28 @@ namespace WebSocketSharp.Server
         return false;
       }
 
-      return _sessions.SendTo (id, data);
+      return _sessions.SendTo (data, id);
     }
 
     /// <summary>
     /// Sends a text data to the client associated with the specified ID.
     /// </summary>
     /// <returns>
-    /// <c>true</c> if the client associated with <paramref name="id"/> is successfully found;
-    /// otherwise, <c>false</c>.
+    /// <c>true</c> if <paramref name="data"/> is successfully sent; otherwise, <c>false</c>.
     /// </returns>
-    /// <param name="id">
-    /// A <see cref="string"/> that contains an ID that represents the destination for the data.
-    /// </param>
     /// <param name="data">
     /// A <see cref="string"/> that contains a text data to send.
     /// </param>
-    public bool SendTo (string id, string data)
+    /// <param name="id">
+    /// A <see cref="string"/> that contains an ID that represents the destination for the data.
+    /// </param>
+    public bool SendTo (string data, string id)
     {
-      var msg = id.IsNullOrEmpty ()
+      var msg = data == null
+              ? "'data' must not be null."
+              : id.IsNullOrEmpty ()
                 ? "'id' must not be null or empty."
-                : data == null
-                  ? "'data' must not be null."
-                  : null;
+                : null;
 
       if (msg != null)
       {
@@ -436,7 +425,7 @@ namespace WebSocketSharp.Server
         return false;
       }
 
-      return _sessions.SendTo (id, data);
+      return _sessions.SendTo (data, id);
     }
 
     /// <summary>
@@ -494,7 +483,7 @@ namespace WebSocketSharp.Server
     /// <param name="context">
     /// A <see cref="WebSocketContext"/> that contains the WebSocket connection request objects to bind.
     /// </param>
-    void IServiceHost.BindWebSocket (WebSocketContext context)
+    void IWebSocketServiceHost.BindWebSocket (WebSocketContext context)
     {
       T service = new T ();
       service.Bind (context, _sessions);
@@ -507,7 +496,7 @@ namespace WebSocketSharp.Server
     /// <param name="data">
     /// An array of <see cref="byte"/> to broadcast.
     /// </param>
-    void IServiceHost.Broadcast (byte [] data)
+    void IWebSocketServiceHost.Broadcast (byte [] data)
     {
       _sessions.Broadcast (data);
     }
@@ -518,78 +507,76 @@ namespace WebSocketSharp.Server
     /// <param name="data">
     /// A <see cref="string"/> to broadcast.
     /// </param>
-    void IServiceHost.Broadcast (string data)
+    void IWebSocketServiceHost.Broadcast (string data)
     {
       _sessions.Broadcast (data);
     }
 
     /// <summary>
-    /// Sends Pings with the specified <see cref="string"/> to all clients.
+    /// Sends Pings with the specified <paramref name="message"/> to all clients.
     /// </summary>
     /// <returns>
-    /// A Dictionary&lt;string, bool&gt; that contains the collection of session IDs and values
-    /// indicating whether the service host received the Pongs from each clients in a time.
+    /// A Dictionary&lt;string, bool&gt; that contains the collection of pairs of session ID and value
+    /// indicating whether the service host received the Pong from each client in a time.
     /// </returns>
     /// <param name="message">
     /// A <see cref="string"/> that contains a message to send.
     /// </param>
-    Dictionary<string, bool> IServiceHost.Broadping (string message)
+    Dictionary<string, bool> IWebSocketServiceHost.Broadping (string message)
     {
       return _sessions.Broadping (message);
     }
 
     /// <summary>
-    /// Sends a Ping with the specified <see cref="string"/> to the client associated with
+    /// Sends a Ping with the specified <paramref name="message"/> to the client associated with
     /// the specified ID.
     /// </summary>
     /// <returns>
     /// <c>true</c> if the service host receives a Pong from the client in a time; otherwise, <c>false</c>.
     /// </returns>
-    /// <param name="id">
-    /// A <see cref="string"/> that contains an ID that represents the destination for the Ping.
-    /// </param>
     /// <param name="message">
     /// A <see cref="string"/> that contains a message to send.
     /// </param>
-    bool IServiceHost.PingTo (string id, string message)
+    /// <param name="id">
+    /// A <see cref="string"/> that contains an ID that represents the destination for the Ping.
+    /// </param>
+    bool IWebSocketServiceHost.PingTo (string message, string id)
     {
-      return _sessions.PingTo (id, message);
+      return _sessions.PingTo (message, id);
     }
 
     /// <summary>
     /// Sends a binary data to the client associated with the specified ID.
     /// </summary>
     /// <returns>
-    /// <c>true</c> if the client associated with <paramref name="id"/> is successfully found;
-    /// otherwise, <c>false</c>.
+    /// <c>true</c> if <paramref name="data"/> is successfully sent; otherwise, <c>false</c>.
     /// </returns>
-    /// <param name="id">
-    /// A <see cref="string"/> that contains an ID that represents the destination for the data.
-    /// </param>
     /// <param name="data">
     /// An array of <see cref="byte"/> that contains a binary data to send.
     /// </param>
-    bool IServiceHost.SendTo (string id, byte [] data)
+    /// <param name="id">
+    /// A <see cref="string"/> that contains an ID that represents the destination for the data.
+    /// </param>
+    bool IWebSocketServiceHost.SendTo (byte [] data, string id)
     {
-      return _sessions.SendTo (id, data);
+      return _sessions.SendTo (data, id);
     }
 
     /// <summary>
     /// Sends a text data to the client associated with the specified ID.
     /// </summary>
     /// <returns>
-    /// <c>true</c> if the client associated with <paramref name="id"/> is successfully found;
-    /// otherwise, <c>false</c>.
+    /// <c>true</c> if <paramref name="data"/> is successfully sent; otherwise, <c>false</c>.
     /// </returns>
-    /// <param name="id">
-    /// A <see cref="string"/> that contains an ID that represents the destination for the data.
-    /// </param>
     /// <param name="data">
     /// A <see cref="string"/> that contains a text data to send.
     /// </param>
-    bool IServiceHost.SendTo (string id, string data)
+    /// <param name="id">
+    /// A <see cref="string"/> that contains an ID that represents the destination for the data.
+    /// </param>
+    bool IWebSocketServiceHost.SendTo (string data, string id)
     {
-      return _sessions.SendTo (id, data);
+      return _sessions.SendTo (data, id);
     }
 
     /// <summary>
@@ -602,7 +589,7 @@ namespace WebSocketSharp.Server
     /// <param name="reason">
     /// A <see cref="string"/> that contains the reason for stop.
     /// </param>
-    void IServiceHost.Stop (ushort code, string reason)
+    void IWebSocketServiceHost.Stop (ushort code, string reason)
     {
       base.Stop ();
       _sessions.Stop (code, reason);
diff --git a/websocket-sharp/Server/WebSocketServiceHostManager.cs b/websocket-sharp/Server/WebSocketServiceHostManager.cs
index c768b99c..0bd1fcf0 100644
--- a/websocket-sharp/Server/WebSocketServiceHostManager.cs
+++ b/websocket-sharp/Server/WebSocketServiceHostManager.cs
@@ -39,10 +39,10 @@ namespace WebSocketSharp.Server
   {
     #region Private Fields
 
-    private volatile bool                    _keepClean;
-    private Logger                           _logger;
-    private Dictionary<string, IServiceHost> _serviceHosts;
-    private object                           _sync;
+    private volatile bool                             _keepClean;
+    private Logger                                    _logger;
+    private Dictionary<string, IWebSocketServiceHost> _serviceHosts;
+    private object                                    _sync;
 
     #endregion
 
@@ -57,7 +57,7 @@ namespace WebSocketSharp.Server
     {
       _logger = logger;
       _keepClean = true;
-      _serviceHosts = new Dictionary<string, IServiceHost> ();
+      _serviceHosts = new Dictionary<string, IWebSocketServiceHost> ();
       _sync = new object ();
     }
 
@@ -133,7 +133,7 @@ namespace WebSocketSharp.Server
       }
     }
 
-    internal IEnumerable<IServiceHost> ServiceHosts {
+    internal IEnumerable<IWebSocketServiceHost> ServiceHosts {
       get {
         lock (_sync)
         {
@@ -146,11 +146,11 @@ namespace WebSocketSharp.Server
 
     #region Private Methods
 
-    private Dictionary<string, IServiceHost> copy ()
+    private Dictionary<string, IWebSocketServiceHost> copy ()
     {
       lock (_sync)
       {
-        return new Dictionary<string, IServiceHost> (_serviceHosts);
+        return new Dictionary<string, IWebSocketServiceHost> (_serviceHosts);
       }
     }
 
@@ -158,15 +158,15 @@ namespace WebSocketSharp.Server
 
     #region Internal Methods
 
-    internal void Add (string servicePath, IServiceHost serviceHost)
+    internal void Add (string servicePath, IWebSocketServiceHost serviceHost)
     {
       lock (_sync)
       {
-        IServiceHost host;
+        IWebSocketServiceHost host;
         if (_serviceHosts.TryGetValue (servicePath, out host))
         {
           _logger.Error (
-            "The WebSocket service host with the specified path already exists.\npath: " + servicePath);
+            "The WebSocket service with the specified path already exists.\npath: " + servicePath);
           return;
         }
 
@@ -176,13 +176,13 @@ namespace WebSocketSharp.Server
 
     internal bool Remove (string servicePath)
     {
-      IServiceHost host;
+      IWebSocketServiceHost host;
       lock (_sync)
       {
         if (!_serviceHosts.TryGetValue (servicePath, out host))
         {
           _logger.Error (
-            "The WebSocket service host with the specified path not found.\npath: " + servicePath);
+            "The WebSocket service with the specified path not found.\npath: " + servicePath);
           return false;
         }
 
@@ -215,7 +215,7 @@ namespace WebSocketSharp.Server
       }
     }
 
-    internal bool TryGetServiceHost (string servicePath, out IServiceHost serviceHost)
+    internal bool TryGetServiceHost (string servicePath, out IWebSocketServiceHost serviceHost)
     {
       lock (_sync)
       {
@@ -290,7 +290,7 @@ namespace WebSocketSharp.Server
         return false;
       }
 
-      IServiceHost host;
+      IWebSocketServiceHost host;
       if (!TryGetServiceHost (servicePath, out host))
       {
         _logger.Error ("The WebSocket service with the specified path not found.\npath: " + servicePath);
@@ -328,7 +328,7 @@ namespace WebSocketSharp.Server
         return false;
       }
 
-      IServiceHost host;
+      IWebSocketServiceHost host;
       if (!TryGetServiceHost (servicePath, out host))
       {
         _logger.Error ("The WebSocket service with the specified path not found.\npath: " + servicePath);
@@ -401,7 +401,7 @@ namespace WebSocketSharp.Server
         return null;
       }
 
-      IServiceHost host;
+      IWebSocketServiceHost host;
       if (!TryGetServiceHost (servicePath, out host))
       {
         _logger.Error ("The WebSocket service with the specified path not found.\npath: " + servicePath);
@@ -429,7 +429,7 @@ namespace WebSocketSharp.Server
         return -1;
       }
 
-      IServiceHost host;
+      IWebSocketServiceHost host;
       if (!TryGetServiceHost (servicePath, out host))
       {
         _logger.Error ("The WebSocket service with the specified path not found.\npath: " + servicePath);
@@ -458,16 +458,11 @@ namespace WebSocketSharp.Server
     /// </param>
     public bool PingTo (string message, string id, string servicePath)
     {
-      if (message == null)
-        message = String.Empty;
-
-      var msg = Encoding.UTF8.GetBytes (message).Length > 125
-              ? "The payload length of a Ping frame must be 125 bytes or less."
-              : id.IsNullOrEmpty ()
-                ? "'id' must not be null or empty."
-                : servicePath.IsNullOrEmpty ()
-                  ? "'servicePath' must not be null or empty."
-                  : null;
+      var msg = id.IsNullOrEmpty ()
+              ? "'id' must not be null or empty."
+              : servicePath.IsNullOrEmpty ()
+                ? "'servicePath' must not be null or empty."
+                : null;
 
       if (msg != null)
       {
@@ -475,14 +470,14 @@ namespace WebSocketSharp.Server
         return false;
       }
 
-      IServiceHost host;
+      IWebSocketServiceHost host;
       if (!TryGetServiceHost (servicePath, out host))
       {
         _logger.Error ("The WebSocket service with the specified path not found.\npath: " + servicePath);
         return false;
       }
 
-      return host.PingTo (id, message);
+      return host.PingTo (message, id);
     }
 
     /// <summary>
@@ -517,14 +512,14 @@ namespace WebSocketSharp.Server
         return false;
       }
 
-      IServiceHost host;
+      IWebSocketServiceHost host;
       if (!TryGetServiceHost (servicePath, out host))
       {
         _logger.Error ("The WebSocket service with the specified path not found.\npath: " + servicePath);
         return false;
       }
 
-      return host.SendTo (id, data);
+      return host.SendTo (data, id);
     }
 
     /// <summary>
@@ -559,14 +554,14 @@ namespace WebSocketSharp.Server
         return false;
       }
 
-      IServiceHost host;
+      IWebSocketServiceHost host;
       if (!TryGetServiceHost (servicePath, out host))
       {
         _logger.Error ("The WebSocket service with the specified path not found.\npath: " + servicePath);
         return false;
       }
 
-      return host.SendTo (id, data);
+      return host.SendTo (data, id);
     }
 
     #endregion
diff --git a/websocket-sharp/Server/WebSocketServiceManager.cs b/websocket-sharp/Server/WebSocketServiceManager.cs
index 5e00e287..a49078a5 100644
--- a/websocket-sharp/Server/WebSocketServiceManager.cs
+++ b/websocket-sharp/Server/WebSocketServiceManager.cs
@@ -361,12 +361,12 @@ namespace WebSocketSharp.Server
     }
 
     /// <summary>
-    /// Sends Pings with the specified <see cref="string"/> to the clients of every
+    /// Sends Pings with the specified <paramref name="message"/> to the clients of every
     /// <see cref="WebSocketService"/> instances managed by the <see cref="WebSocketServiceManager"/>.
     /// </summary>
     /// <returns>
-    /// A Dictionary&lt;string, bool&gt; that contains the collection of IDs and values indicating
-    /// whether each <see cref="WebSocketService"/> instances received a Pong in a time.
+    /// A Dictionary&lt;string, bool&gt; that contains the collection of pairs of session ID and value
+    /// indicating whether the each <see cref="WebSocketService"/> instance received a Pong in a time.
     /// </returns>
     /// <param name="message">
     /// A <see cref="string"/> that contains a message to send.
@@ -381,28 +381,30 @@ namespace WebSocketSharp.Server
     }
 
     /// <summary>
-    /// Sends a Ping with the specified <see cref="string"/> to the client of the <see cref="WebSocketService"/>
-    /// instance with the specified ID.
+    /// Sends a Ping with the specified <paramref name="message"/> to the client of
+    /// the <see cref="WebSocketService"/> instance with the specified ID.
     /// </summary>
     /// <returns>
-    /// <c>true</c> if the <see cref="WebSocketService"/> instance receives a Pong in a time;
-    /// otherwise, <c>false</c>.
+    /// <c>true</c> if the <see cref="WebSocketService"/> instance with <paramref name="id"/> receives
+    /// a Pong in a time; otherwise, <c>false</c>.
     /// </returns>
-    /// <param name="id">
-    /// A <see cref="string"/> that contains an ID that represents the destination for the Ping.
-    /// </param>
     /// <param name="message">
     /// A <see cref="string"/> that contains a message to send.
     /// </param>
-    internal bool PingTo (string id, string message)
+    /// <param name="id">
+    /// A <see cref="string"/> that contains an ID that represents the destination for the Ping.
+    /// </param>
+    internal bool PingTo (string message, string id)
     {
       WebSocketService service;
-      if (TryGetServiceInstance (id, out service))
-        return service.Ping (message);
+      if (!TryGetServiceInstance (id, out service))
+      {
+        _logger.Error (
+          "The WebSocket service instance with the specified ID not found.\nID: " + id);
+        return false;
+      }
 
-      _logger.Error (
-        "The WebSocket service instance with the specified ID not found.\nID: " + id);
-      return false;
+      return service.Ping (message);
     }
 
     internal bool Remove (string id)
@@ -418,27 +420,26 @@ namespace WebSocketSharp.Server
     /// with the specified ID.
     /// </summary>
     /// <returns>
-    /// <c>true</c> if the <see cref="WebSocketService"/> instance with <paramref name="id"/>
-    /// is successfully found; otherwise, <c>false</c>.
+    /// <c>true</c> if <paramref name="data"/> is successfully sent; otherwise, <c>false</c>.
     /// </returns>
-    /// <param name="id">
-    /// A <see cref="string"/> that contains an ID that represents the destination for the data.
-    /// </param>
     /// <param name="data">
     /// An array of <see cref="byte"/> that contains a binary data to send.
     /// </param>
-    internal bool SendTo (string id, byte [] data)
+    /// <param name="id">
+    /// A <see cref="string"/> that contains an ID that represents the destination for the data.
+    /// </param>
+    internal bool SendTo (byte [] data, string id)
     {
       WebSocketService service;
-      if (TryGetServiceInstance (id, out service))
+      if (!TryGetServiceInstance (id, out service))
       {
-        service.Send (data);
-        return true;
+        _logger.Error (
+          "The WebSocket service instance with the specified ID not found.\nID: " + id);
+        return false;
       }
 
-      _logger.Error (
-        "The WebSocket service instance with the specified ID not found.\nID: " + id);
-      return false;
+      service.Send (data);
+      return true;
     }
 
     /// <summary>
@@ -446,27 +447,26 @@ namespace WebSocketSharp.Server
     /// with the specified ID.
     /// </summary>
     /// <returns>
-    /// <c>true</c> if the <see cref="WebSocketService"/> instance with <paramref name="id"/>
-    /// is successfully found; otherwise, <c>false</c>.
+    /// <c>true</c> if <paramref name="data"/> is successfully sent; otherwise, <c>false</c>.
     /// </returns>
-    /// <param name="id">
-    /// A <see cref="string"/> that contains an ID that represents the destination for the data.
-    /// </param>
     /// <param name="data">
     /// A <see cref="string"/> that contains a text data to send.
     /// </param>
-    internal bool SendTo (string id, string data)
+    /// <param name="id">
+    /// A <see cref="string"/> that contains an ID that represents the destination for the data.
+    /// </param>
+    internal bool SendTo (string data, string id)
     {
       WebSocketService service;
-      if (TryGetServiceInstance (id, out service))
+      if (!TryGetServiceInstance (id, out service))
       {
-        service.Send (data);
-        return true;
+        _logger.Error (
+          "The WebSocket service instance with the specified ID not found.\nID: " + id);
+        return false;
       }
 
-      _logger.Error (
-        "The WebSocket service instance with the specified ID not found.\nID: " + id);
-      return false;
+      service.Send (data);
+      return true;
     }
 
     internal void Stop ()
@@ -499,10 +499,7 @@ namespace WebSocketSharp.Server
           lock (_sync)
           {
             if (_stopped)
-            {
-              _sweeping = false;
-              return;
-            }
+              break;
 
             WebSocketService service;
             if (_services.TryGetValue (id, out service))
diff --git a/websocket-sharp/websocket-sharp.csproj b/websocket-sharp/websocket-sharp.csproj
index cc1147e0..7d778d9a 100644
--- a/websocket-sharp/websocket-sharp.csproj
+++ b/websocket-sharp/websocket-sharp.csproj
@@ -100,7 +100,6 @@
     <Compile Include="Net\HttpStatusCode.cs" />
     <Compile Include="Server\WebSocketServerBase.cs" />
     <Compile Include="Net\Security\SslStream.cs" />
-    <Compile Include="Server\IServiceHost.cs" />
     <Compile Include="Server\WebSocketServiceHost.cs" />
     <Compile Include="CloseStatusCode.cs" />
     <Compile Include="Fin.cs" />
@@ -128,6 +127,7 @@
     <Compile Include="HandshakeRequest.cs" />
     <Compile Include="HandshakeResponse.cs" />
     <Compile Include="Server\WebSocketServiceHostManager.cs" />
+    <Compile Include="Server\IWebSocketServiceHost.cs" />
   </ItemGroup>
   <Import Project="$(MSBuildBinPath)\Microsoft.CSharp.targets" />
   <ItemGroup>