diff --git a/Samples/ClientJs/Program.cs b/Samples/ClientJs/Program.cs
index ce3977a..0f2fa5f 100644
--- a/Samples/ClientJs/Program.cs
+++ b/Samples/ClientJs/Program.cs
@@ -6,13 +6,29 @@
 
 namespace TestClientJs
 {
+    /// <summary>
+    /// Remote API.
+    /// </summary>
     interface IRemoteAPI
     {
+        /// <summary>
+        /// Writes progress.
+        /// </summary>
+        /// <param name="progress">Progress value [0..1].</param>
         void WriteProgress(float progress);
     }
 
+    /// <summary>
+    /// Local API.
+    /// </summary>
     class LocalAPI
     {
+        /// <summary>
+        /// Executes long running addition task.
+        /// </summary>
+        /// <param name="a">First number.</param>
+        /// <param name="b">Second number.</param>
+        /// <returns>Result.</returns>
         public async Task<int> LongRunningTask(int a, int b)
         {
             for (var p = 0; p <= 100; p += 5)
@@ -25,7 +41,7 @@ public async Task<int> LongRunningTask(int a, int b)
         }
     }
 
-    public class Program
+    class Program
     {
         //if access denied execute: "netsh http delete urlacl url=http://+:8001/"
         //open Index.html to run the client
diff --git a/Samples/ClientJs/ServerClientJs.csproj b/Samples/ClientJs/ServerClientJs.csproj
index ad5aaee..82638f2 100644
--- a/Samples/ClientJs/ServerClientJs.csproj
+++ b/Samples/ClientJs/ServerClientJs.csproj
@@ -22,6 +22,7 @@
     <ErrorReport>prompt</ErrorReport>
     <WarningLevel>4</WarningLevel>
     <Prefer32Bit>false</Prefer32Bit>
+    <DocumentationFile>bin\ClientJs.xml</DocumentationFile>
   </PropertyGroup>
   <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Release|AnyCPU' ">
     <DebugType>pdbonly</DebugType>
@@ -31,6 +32,7 @@
     <ErrorReport>prompt</ErrorReport>
     <WarningLevel>4</WarningLevel>
     <Prefer32Bit>false</Prefer32Bit>
+    <DocumentationFile>bin\ClientJs.xml</DocumentationFile>
   </PropertyGroup>
   <PropertyGroup>
     <StartupObject />
diff --git a/Samples/MultiService/MultiService.csproj b/Samples/MultiService/MultiService.csproj
index 6eceac2..b8ab050 100644
--- a/Samples/MultiService/MultiService.csproj
+++ b/Samples/MultiService/MultiService.csproj
@@ -21,6 +21,7 @@
     <DefineConstants>DEBUG;TRACE</DefineConstants>
     <ErrorReport>prompt</ErrorReport>
     <WarningLevel>4</WarningLevel>
+    <DocumentationFile>bin\ClientJsMultiService.xml</DocumentationFile>
   </PropertyGroup>
   <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Release|AnyCPU' ">
     <DebugType>pdbonly</DebugType>
@@ -29,6 +30,7 @@
     <DefineConstants>TRACE</DefineConstants>
     <ErrorReport>prompt</ErrorReport>
     <WarningLevel>4</WarningLevel>
+    <DocumentationFile>bin\ClientJsMultiService.xml</DocumentationFile>
   </PropertyGroup>
   <PropertyGroup>
     <StartupObject />
diff --git a/Samples/MultiService/Program.cs b/Samples/MultiService/Program.cs
index 58dbb13..6d3c5e7 100644
--- a/Samples/MultiService/Program.cs
+++ b/Samples/MultiService/Program.cs
@@ -8,7 +8,7 @@ namespace ClientJsMultiService
     /// <summary>
     /// Numeric service providing operations on numbers.
     /// </summary>
-    public class NumericService
+    class NumericService
     {
         /// <summary>
         /// Adds two numbers.
@@ -25,7 +25,7 @@ public int Add(int a, int b)
     /// <summary>
     /// Text service providing operations on strings.
     /// </summary>
-    public class TextService
+    class TextService
     {
         /// <summary>
         /// Concatenates two strings.
@@ -39,7 +39,7 @@ public string Add(string a, string b)
         }
     }
 
-    public class Program
+    class Program
     {
         //if access denied execute: "netsh http delete urlacl url=http://+:8001/"
         //open Index.html to run the client
diff --git a/Samples/Serialization/Program.cs b/Samples/Serialization/Program.cs
index 3062666..4d3f977 100644
--- a/Samples/Serialization/Program.cs
+++ b/Samples/Serialization/Program.cs
@@ -38,7 +38,7 @@ public override object ReadJson(JsonReader reader, Type objectType, object exist
     /// <summary>
     /// The image processing service API.
     /// </summary>
-    public class ImageProcessingAPI
+    class ImageProcessingAPI
     {
         const int CHANNEL_COUNT = 3;
 
diff --git a/Samples/ServerClientSample/Client/Program.cs b/Samples/ServerClientSample/Client/Program.cs
index beb9815..5f3f575 100644
--- a/Samples/ServerClientSample/Client/Program.cs
+++ b/Samples/ServerClientSample/Client/Program.cs
@@ -6,12 +6,12 @@
 
 namespace TestClient
 {
-    public interface ILocalAPI
+    interface ILocalAPI
     {
         Task<int> LongRunningTask(int a, int b);
     }
 
-    public class RemoteAPI //:IRemoteAPI
+    class RemoteAPI //:IRemoteAPI
     {
         public void WriteProgress(float progress)
         {
diff --git a/Source/WebSocketRPC.JS/ClientAPIBase.js b/Source/WebSocketRPC.JS/ClientAPIBase.js
index fdfe3d7..73e1c41 100644
--- a/Source/WebSocketRPC.JS/ClientAPIBase.js
+++ b/Source/WebSocketRPC.JS/ClientAPIBase.js
@@ -83,6 +83,16 @@ function onMessage(msg, onError)
 */
 this.connect = function (onOpen, onError, onClose)
 {
+    if (!!onOpen === false || typeof onOpen !== 'function')
+        throw 'OnOpen function callback is missing.';
+
+    if (!!onError === false || typeof onError !== 'function')
+        throw 'OnError function callback is missing.';
+
+    if (!!onClose === false || typeof onClose !== 'function')
+        throw 'OnClose function callback is missing.';
+
+
     if (!!window.WebSocket === false)
         onError({ id: -1, title: "SOCKET_NOSUPPORT", summary: "This browser does not support Web sockets." });
 
@@ -146,7 +156,7 @@ this.onOtherMessage = null;
 this.send = (msg) => ws.send(msg);
 
 /*
- * CLoses the underlying websocket connection.
+ * Closes the underlying websocket connection.
  * @param {number} - Status code (see https://developer.mozilla.org/en-US/docs/Web/API/CloseEvent#Status_codes for details).
  * @param {string} - Human readable close reason (the max length is 123 bytes / ASCII characters).
 */