Added MQTT JS examples for MQTTnet.Server.

Build/MQTTnet.nuspec

@@ -12,22 +12,9 @@
     <requireLicenseAcceptance>true</requireLicenseAcceptance>
     <description>MQTTnet is a high performance .NET library for MQTT based communication. It provides a MQTT client and a MQTT server (broker) and supports v3.1.0, v3.1.1 and v5.0.0 of the MQTT protocol.</description>
     <releaseNotes>
-* [Core] Improved logger performance (BREAKING CHANGE!).
-* [Core] Renamed some topic filter relevant classes (BREAKING CHANGE!).
-* [Core] Improved task management for UWP connections (thanks to @xgstation).
-* [Core] Fixed broken logger which decreases overall performance.
-* [Core] Fixed issue in closed socket detection (fixes high CPU load issue).
-* [Client] Added method to trigger PING/PONG manually (connection check etc.).
-* [Client] Added support for certificate validation callback when using Web Sockets (requires netstandard2.1+).
-* [Client] Fixed a memory leak when web socket based connections trying to reconnect with an offline server.
-* [Client] Fixed a memory leak when TCP based connections trying to reconnect with an offline server.
-* [Client] Fixed an issue when connecting to an invalid host (format).
-* [Client] Added support for user properties in CONNECT packet.
-* [Client] Removed _KeepAliveSendInterval_ and improved keep alive handling (BREAKING CHANGE!).
-* [ManagedClient] Added method to trigger PING/PONG manually (connection check etc.).
-* [MQTTnet.AspNetCore] improved compatibility with AspNetCore 3.1.
-* [MQTTnet.AspNetCore] Fixed several packaging issues with the Nuget package.
-* [MQTTnet.Server] Fixed wrong version output.
+* [Client] Fixed issue in keep alive handling.
+* [MQTTnet.Server] Added support for delivering static files (HTML, JavaScript etc.).
+* [MQTTnet.Server] Fixed web socket protocol errors (when using paho JS etc.).
     </releaseNotes>
     <copyright>Copyright Christian Kratky 2016-2020</copyright>
     <tags>MQTT Message Queue Telemetry Transport MQTTClient MQTTServer Server MQTTBroker Broker NETStandard IoT InternetOfThings Messaging Hardware Arduino Sensor Actuator M2M ESP Smart Home Cities Automation Xamarin</tags> 

Source/MQTTnet.Server/MQTTnet.Server.csproj

@@ -29,13 +29,6 @@
     <NoWarn>1701;1702</NoWarn>
   </PropertyGroup>
 
-  <ItemGroup>
-    <Compile Remove="wwwroot\**" />
-    <Content Remove="wwwroot\**" />
-    <EmbeddedResource Remove="wwwroot\**" />
-    <None Remove="wwwroot\**" />
-  </ItemGroup>
-
   <ItemGroup>
     <Content Update="appsettings.json">
       <CopyToOutputDirectory>Always</CopyToOutputDirectory>
@@ -72,11 +65,19 @@
     <None Update="Web\authorization_handler.py">
       <CopyToOutputDirectory>Always</CopyToOutputDirectory>
     </None>
+    <None Update="Web\wwwroot\Hello.txt">
+      <CopyToOutputDirectory>Always</CopyToOutputDirectory>
+    </None>
+    <None Update="Web\wwwroot\mqtt_Test.html">
+      <CopyToOutputDirectory>Always</CopyToOutputDirectory>
+    </None>
+    <None Update="Web\wwwroot\pahoJS_Test.html">
+      <CopyToOutputDirectory>Always</CopyToOutputDirectory>
+    </None>
   </ItemGroup>
 
   <ItemGroup>
     <Folder Include="Properties\PublishProfiles\" />
-    <Folder Include="Web\wwwroot\" />
   </ItemGroup>
 
 </Project>

Source/MQTTnet.Server/Program.cs

@@ -3,6 +3,7 @@ using Microsoft.Extensions.Hosting;
 using MQTTnet.Server.Web;
 using System;
 using System.Diagnostics;
+using System.IO;
 using System.Reflection;
 
 namespace MQTTnet.Server
@@ -21,8 +22,8 @@ namespace MQTTnet.Server
                         webBuilder.ConfigureKestrel(serverOptions =>
                         {
                         })
+                        .UseWebRoot(Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "Web", "wwwroot"))
                         .UseStartup<Startup>();
-
                     }).Build().Run();
 
                 return 0;

Source/MQTTnet.Server/Web/Startup.cs

@@ -6,6 +6,7 @@ using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Net.Http.Headers;
 using Microsoft.OpenApi.Models;
 using Microsoft.Scripting.Utils;
+using MQTTnet.AspNetCore;
 using MQTTnet.Server.Configuration;
 using MQTTnet.Server.Logging;
 using MQTTnet.Server.Mqtt;
@@ -40,6 +41,9 @@ namespace MQTTnet.Server.Web
             DataSharingService dataSharingService,
             MqttSettingsModel mqttSettings)
         {
+            application.UseDefaultFiles();
+            application.UseStaticFiles();
+
             application.UseHsts();
             application.UseRouting();
             application.UseCors(x => x
@@ -49,9 +53,7 @@ namespace MQTTnet.Server.Web
 
             application.UseAuthentication();
             application.UseAuthorization();
-
-            application.UseStaticFiles();
-
+     
             application.UseEndpoints(endpoints =>
             {
                 endpoints.MapControllers();
@@ -81,7 +83,6 @@ namespace MQTTnet.Server.Web
         {
             services.AddCors();
 
-
             services.AddControllers();
 
             services.AddMvc()
@@ -197,7 +198,13 @@ namespace MQTTnet.Server.Web
                 {
                     if (context.WebSockets.IsWebSocketRequest)
                     {
-                        using (var webSocket = await context.WebSockets.AcceptWebSocketAsync().ConfigureAwait(false))
+                        string subProtocol = null;
+                        if (context.Request.Headers.TryGetValue("Sec-WebSocket-Protocol", out var requestedSubProtocolValues))
+                        {
+                            subProtocol = MqttSubProtocolSelector.SelectSubProtocol(requestedSubProtocolValues);
+                        }
+
+                        using (var webSocket = await context.WebSockets.AcceptWebSocketAsync(subProtocol).ConfigureAwait(false))
                         {
                             await mqttServerService.RunWebSocketConnectionAsync(webSocket, context).ConfigureAwait(false);
                         }

Source/MQTTnet.Server/Web/wwwroot/Hello.txt

@@ -0,0 +1 @@
+World

Source/MQTTnet.Server/Web/wwwroot/mqtt_Test.html

@@ -0,0 +1,33 @@
+<html>
+
+<head>
+    <title>MQTT JS Example</title>
+
+    <script src="https://cdn.jsdelivr.net/npm/mqtt@4.0.1/dist/mqtt.min.js" type="text/javascript"></script>
+
+    <script type="text/javascript">
+        var client = mqtt.connect('ws://localhost:80/mqtt')
+
+        client.on('connect', function () {
+            client.subscribe('mqtt_subscription', function (err) {
+                console.log("Subscribed");
+            })
+        })
+
+        client.on('message', function (topic, message) {
+            console.log(topic);
+            console.log(message.toString())
+        })
+
+        function buttonClick() {
+            client.publish("MQTT_JS_TOPIC", "payload");
+        }
+    </script>
+
+</head>
+
+<body>
+    <button onclick="buttonClick()">Publish</button>
+</body>
+
+</html>

Source/MQTTnet.Server/Web/wwwroot/pahoJS_Test.html

@@ -0,0 +1,41 @@
+<html>
+
+<head>
+    <title>paho JS Example</title>
+
+    <script src="https://cdnjs.cloudflare.com/ajax/libs/paho-mqtt/1.0.1/mqttws31.js" type="text/javascript"></script>
+
+    <script type="text/javascript">
+        var mqttClient = new Paho.MQTT.Client("localhost", 80, "/mqtt", "pahoJS_client");
+        mqttClient.onConnectionLost = onConnectionLost;
+        mqttClient.onMessageArrived = onMessageArrived;
+        mqttClient.connect({ onSuccess: onConnect });
+
+        function onConnect() {
+            console.log("MQTT client connected");
+            mqttClient.subscribe("pahoJS_subscription");
+        }
+
+        function onConnectionLost(responseObject) {
+            if (responseObject.errorCode !== 0) {
+                console.log("onConnectionLost:" + responseObject.errorMessage);
+            }
+        }
+
+        function onMessageArrived(message) {
+            console.log("onMessageArrived:" + message.payloadString);
+        }
+        function buttonClick() {
+            message = new Paho.MQTT.Message("Hello");
+            message.destinationName = "pahoJS_topic";
+            mqttClient.send(message);
+        }
+    </script>
+
+</head>
+
+<body>
+    <button onclick="buttonClick()">Publish</button>
+</body>
+
+</html>

Source/MQTTnet/Adapter/MqttChannelAdapter.cs

@@ -25,7 +25,7 @@ namespace MQTTnet.Adapter
 
         readonly byte[] _fixedHeaderBuffer = new byte[2];
 
-        SemaphoreSlim _writerSemaphore = new SemaphoreSlim(1, 1);
+        readonly SemaphoreSlim _writerSemaphore = new SemaphoreSlim(1, 1);
 
         long _bytesReceived;
         long _bytesSent;
@@ -111,6 +111,8 @@ namespace MQTTnet.Adapter
 
         public async Task SendPacketAsync(MqttBasePacket packet, TimeSpan timeout, CancellationToken cancellationToken)
         {
+            ThrowIfDisposed();
+
             await _writerSemaphore.WaitAsync(cancellationToken).ConfigureAwait(false);
             try
             {
@@ -211,9 +213,7 @@ namespace MQTTnet.Adapter
             if (disposing)
             {
                 _channel?.Dispose();
-
                 _writerSemaphore?.Dispose();
-                _writerSemaphore = null;
             }
 
             base.Dispose(disposing);

Source/MQTTnet/Client/MqttClient.cs

@@ -446,7 +446,11 @@ namespace MQTTnet.Client
                         await SendAndReceiveAsync<MqttPingRespPacket>(new MqttPingReqPacket(), cancellationToken).ConfigureAwait(false);
                     }
 
-                    await Task.Delay(keepAlivePeriod, cancellationToken).ConfigureAwait(false);
+                    // Wait a fixed time in all cases. Calculation of the remaining time is complicated
+                    // due to some edge cases and was buggy in the past. Now we wait half a second because the
+                    // min keep alive value is one second so that the server will wait 1.5 seconds for a PING
+                    // packet.
+                    await Task.Delay(TimeSpan.FromMilliseconds(100), cancellationToken).ConfigureAwait(false);
                 }
             }
             catch (Exception exception)