MqttClient hangs on ConnectAsync

[fdundjer]

Describe the bug

IMqttClient instance hangs on ConnectAsync when trying to connect to a MQTT server while internet connection is off.

Which project is your bug related to?

• Client

Basic Information

MQTTnet version: 3.0.11 Xamarin.Forms version: 4.7.0.1179 Platform: Android Device: Samsung SM-G937F, Android 10 - API 29

To Reproduce

Steps to reproduce the behavior:

1. Make sure that internet connection is off on a mobile device
2. Start application
3. Try to connect to a mqtt server
4. Application will hang on ConnectAsync method

Expected behavior

• Client should cancel the operation and throw exception after cancellation is requested

Code example

var serverIpAddress = "176.222.222.222";
var serverPort = 1883;
try
{
    if (!Uri.TryCreate($"http://{serverIpAddress}:{serverPort}", UriKind.Absolute, out var uri) ||
        !IPAddress.TryParse(uri.Host, out _))
    {
        return;
    }

    var clientOptions = new MqttClientOptionsBuilder()
        .WithClientId(Guid.NewGuid().ToString())
        .WithCredentials(string.Empty, string.Empty)
        .WithTcpServer(uri.Host, uri.Port)
        .Build();

    var client = _mqttFactory.CreateMqttClient();

    // Timeout is one second
    using (var cancellationToken = new CancellationTokenSource(TimeSpan.FromSeconds(1)))
    {
        // Client hangs on a line below
        await client.ConnectAsync(clientOptions, cancellationToken.Token).ConfigureAwait(false);
    }
}
catch (Exception e)
{
    // ignored
}

ps. Let me know if you need example application/code :)

[chkr1011]

Do you have more details or a full solution which has this issue? I also use MQTTnet in a Xamarin application and I cannot reproduce the issue.

What exactly do you mean with "internet connection is off"? Is Wifi AND Cellular just deactivated? Or is no WiFi in range etc?

[fdundjer]

Hi, here is the sample: https://github.com/fdundjer/MqttPlayground Deactivate Wifi and Cellular, so no connection at all. Type IP: 176.222.222.222 and port 1883 in input fields.

[xmaux72]

it's a huge bug... any news?

[redradist]

I have the same issue, but when Server is down then ManagedMqttClient is hang up ... When it will be fixed ? Is there any news ?

@chkr1011 Seems like it use too many threads ...

"Thread Pool Worker"
"Thread Pool Worker"09-29 01:00:17.671 I/system_server( 1285): libdebuggerd_client: started dumping process 11552
09-29 01:00:17.671 D/AppEyeBinderBlock( 1285): read binder transaction begin
09-29 01:00:17.671 I/system_server( 1285): libdebuggerd_client: started dumping process 11552
09-29 01:00:17.672 I//system/bin/tombstoned(  763): registered intercept for pid 11552 and type kDebuggerdJavaBacktrace
09-29 01:00:17.675 E/mono    (11552): Full thread dump:

"Timer-Scheduler"  at <unknown> <0xffffffff>
  at (wrapper managed-to-native) System.Threading.WaitHandle.Wait_internal (intptr*,int,bool,int) <0x00007>
  at System.Threading.WaitHandle.WaitOneNative (System.Runtime.InteropServices.SafeHandle,uint,bool,bool) [0x00019] in /Users/builder/jenkins/workspace/archive-mono/2020-02/android/release/mcs/class/corlib/System.Threading/WaitHandle.cs:90
  at System.Threading.WaitHandle.InternalWaitOne (System.Runtime.InteropServices.SafeHandle,long,bool,bool) [0x00014] in /Users/builder/jenkins/workspace/archive-mono/2020-02/android/release/mcs/class/referencesource/mscorlib/system/threading/waithandle.cs:259
  at System.Threading.WaitHandle.WaitOne (long,bool) [0x00000] in /Users/builder/jenkins/workspace/archive-mono/2020-02/android/release/mcs/class/referencesource/mscorlib/system/threading/waithandle.cs:248
  at System.Threading.WaitHandle.WaitOne (int,bool) [0x00019] in /Users/builder/jenkins/workspace/archive-mono/2020-02/android/release/mcs/class/referencesource/mscorlib/system/threading/waithandle.cs:215
  at System.Threading.WaitHandle.WaitOne (int) [0x00000] in /Users/builder/jenkins/workspace/archive-mono/2020-02/android/release/mcs/class/referencesource/mscorlib/system/threading/waithandle.cs:236
  at System.Threading.Timer/Scheduler.SchedulerThread () [0x0003c] in /Users/builder/jenkins/workspace/archive-mono/2020-02/android/release/mcs/class/corlib/System.Threading/Timer.cs:293
  at System.Threading.ThreadHelper.ThreadStart_Context (object) [0x00014] in /Users/builder/jenkins/workspace/archive-mono/2020-02/android/release/mcs/class/referencesource/mscorlib/system/threading/thread.cs:74
  at System.Threading.ExecutionContext.RunInternal (System.Threading.ExecutionContext,System.Threading.ContextCallback,object,bool) [0x00071] in /Users/builder/jenkins/workspace/archive-mono/2020-02/android/release/mcs/class/referencesource/mscorlib/system/threading/executioncontext.cs:968
  at System.Threading.ExecutionContext.Run (System.Threading.ExecutionContext,System.Threading.ContextCallback,object,bool) [0x00000] in /Users/builder/jenkins/workspace/archive-mono/2020-02/android/release/mcs/class/referencesource/mscorlib/system/threading/executioncontext.cs:910
  at System.Threading.ExecutionContext.Run (System.Threading.ExecutionContext,System.Threading.ContextCallback,object) [0x0002b] in /Users/builder/jenkins/workspace/archive-mono/2020-02/android/release/mcs/class/referencesource/mscorlib/system/threading/executioncontext.cs:899
  at System.Threading.ThreadHelper.ThreadStart () [0x00008] in /Users/builder/jenkins/workspace/archive-mono/2020-02/android/release/mcs/class/referencesource/mscorlib/system/threading/thread.cs:111
  at (wrapper runtime-invoke) object.runtime_invoke_void__this__ (object,intptr,intptr,intptr) [0x00067] in <0381c8f952fb47759ee29160e807b17d>:0

"Thread Pool Worker"
"Thread Pool Worker"
"<threadpool thread>"
"Thread Pool I/O Selector"09-29 01:00:17.687 I/TrafficMonitor( 1285): expired arrive. level:-1
09-29 01:00:17.688 I/TrafficMonitor( 1285): update:rxPkts:2,txPkts:0,rxBytes:402,txBytes:0
09-29 01:00:17.689 I/TrafficMonitor( 1285): start expired. level:-1
09-29 01:00:17.689 I/TrafficMonitor( 1285): gettimer:interval=5000
09-29 01:00:17.689 I/TrafficMonitor( 1285): during_ms:5002,period_ms:2000
09-29 01:00:17.689 I/TrafficMonitor( 1285): count:523,rx_sum:2,tx_sum:0,rxBytes:402,during_ms:5002,rx_speed:80.36785285885647,tx_speed:0.0,rto:0.0

"<unnamed thread>"  at <unknown> <0xffffffff>
  at System.Collections.Generic.List`1<Xamarin.Forms.WeakEventManager/Subscription>.EnsureCapacity (int) [0x00036] in /Users/builder/jenkins/workspace/archive-mono/2020-02/android/release/external/corefx/src/Common/src/CoreLib/System/Collections/Generic/List.cs:426
  at System.Collections.Generic.List`1<Xamarin.Forms.WeakEventManager/Subscription>.AddWithResize (Xamarin.Forms.WeakEventManager/Subscription) [0x00007] in /Users/builder/jenkins/workspace/archive-mono/2020-02/android/release/external/corefx/src/Common/src/CoreLib/System/Collections/Generic/List.cs:231
  at System.Collections.Generic.List`1<Xamarin.Forms.WeakEventManager/Subscription>.Add (Xamarin.Forms.WeakEventManager/Subscription) [0x00034] in /Users/builder/jenkins/workspace/archive-mono/2020-02/android/release/external/corefx/src/Common/src/CoreLib/System/Collections/Generic/List.cs:222
  at Xamarin.Forms.WeakEventManager.AddEventHandler (string,object,System.Reflection.MethodInfo) [0x00034] in D:\a\1\s\Xamarin.Forms.Core\WeakEventManager.cs:116
  at Xamarin.Forms.WeakEventManager.AddEventHandler (System.EventHandler,string) [0x00021] in D:\a\1\s\Xamarin.Forms.Core\WeakEventManager.cs:34
  at Xamarin.Forms.ImageSource.add_SourceChanged (System.EventHandler) [0x00000] in D:\a\1\s\Xamarin.Forms.Core\ImageSource.cs:150
  at Xamarin.Forms.ImageElement.OnImageSourceChanged (Xamarin.Forms.BindableObject,object,object) [0x00014] in D:\a\1\s\Xamarin.Forms.Core\ImageElement.cs:25
  at Xamarin.Forms.BindableObject.SetValueActual (Xamarin.Forms.BindableProperty,Xamarin.Forms.BindableObject/BindablePropertyContext,object,bool,Xamarin.Forms.Internals.SetValueFlags,bool) [0x00120] in D:\a\1\s\Xamarin.Forms.Core\BindableObject.cs:463
  at Xamarin.Forms.BindableObject.SetValueCore (Xamarin.Forms.BindableProperty,object,Xamarin.Forms.Internals.SetValueFlags,Xamarin.Forms.BindableObject/SetValuePrivateFlags) [0x00173] in D:\a\1\s\Xamarin.Forms.Core\BindableObject.cs:397
  at Xamarin.Forms.BindingExpression.ApplyCore (object,Xamarin.Forms.BindableObject,Xamarin.Forms.BindableProperty,bool) [0x00214] in D:\a\1\s\Xamarin.Forms.Core\BindingExpression.cs:155
  at Xamarin.Forms.BindingExpression.Apply (object,Xamarin.Forms.BindableObject,Xamarin.Forms.BindableProperty) [0x0006b] in D:\a\1\s\Xamarin.Forms.Core\BindingExpression.cs:72
  at Xamarin.Forms.Binding.Apply (object,Xamarin.Forms.BindableObject,Xamarin.Forms.BindableProperty,bool) [0x0006d] in D:\a\1\s\Xamarin.Forms.Core\Binding.cs:138
  at Xamarin.Forms.BindableObject.ApplyBindings (bool,bool) [0x00041] in D:\a\1\s\Xamarin.Forms.Core\BindableObject.cs:480
  at Xamarin.Forms.BindableObject.SetInheritedBindingContext (Xamarin.Forms.BindableObject,object) [0x0005a] in D:\a\1\s\Xamarin.Forms.Core\BindableObject.cs:209
  at Xamarin.Forms.Element.SetChildInheritedBindingContext (Xamarin.Forms.Element,object) [0x00000] in D:\a\1\s\Xamarin.Forms.Core\Element.cs:475
  at Xamarin.Forms.Element.<OnBindingContextChanged>b__82_0 (Xamarin.Forms.BindableObject,object) [0x00000] in D:\a\1\s\Xamarin.Forms.Core\Element.cs:306
  at Xamarin.Forms.BindableObjectExtensions.PropagateBindingContext<T_REF> (Xamarin.Forms.BindableObject,System.Collections.Generic.IList`1<T_REF>,System.Action`2<Xamarin.Forms.BindableObject, object>) [0x0002c] in D:\a\1\s\Xamarin.Forms.Core\BindableObjectExtensions.cs:28
  at Xamarin.Forms.Element.OnBindingContextChanged () [0x00000] in D:\a\1\s\Xamarin.Forms.Core\Element.cs:304
  at Xamarin.Forms.VisualElement.OnBindingContextChanged () [0x00006] in D:\a\1\s\Xamarin.Forms.Core\VisualElement.cs:769
  at Xamarin.Forms.View.OnBindingContextChanged () [0x0000c] in D:\a\1\s\Xamarin.Forms.Core\View.cs:158
  at Xamarin.Forms.Grid.OnBindingContextChanged () [0x00006] in D:\a\1\s\Xamarin.Forms.Core\Grid.cs:149
  at Xamarin.Forms.BindableObject.BindingContextPropertyChanged (Xamarin.Forms.BindableObject,object,object) [0x0000f] in D:\a\1\s\Xamarin.Forms.Core\BindableObject.cs:500
  at Xamarin.Forms.BindableObject.SetValueActual (Xamarin.Forms.BindableProperty,Xamarin.Forms.BindableObject/BindablePropertyContext,object,bool,Xamarin.Forms.Internals.SetValueFlags,bool) [0x00120] in D:\a\1\s\Xamarin.Forms.Core\BindableObject.cs:463
  at Xamarin.Forms.BindableObject.SetValueCore (Xamarin.Forms.BindableProperty,object,Xamarin.Forms.Internals.SetValueFlags,Xamarin.Forms.BindableObject/SetValuePrivateFlags) [0x00173] in D:\a\1\s\Xamarin.Forms.Core\BindableObject.cs:397
  at Xamarin.Forms.BindableObject.SetValue (Xamarin.Forms.BindableProperty,object,bool,bool) [0x00042] in D:\a\1\s\Xamarin.Forms.Core\BindableObject.cs:334
  at Xamarin.Forms.BindableObject.SetValue (Xamarin.Forms.BindableProperty,object) [0x00000] in D:\a\1\s\Xamarin.Forms.Core\BindableObject.cs:311
  at Xamarin.Forms.BindableObject.set_BindingContext (object) [0x00000] in D:\a\1\s\Xamarin.Forms.Core\BindableObject.cs:41
  at Xamarin.Forms.Platform.Android.ShellFlyoutRecyclerAdapter/ElementViewHolder.set_Element (Xamarin.Forms.Element) [0x0004d] in D:\a\1\s\Xamarin.Forms.Platform.Android\Renderers\ShellFlyoutRecyclerAdapter.cs:272
  at Xamarin.Forms.Platform.Android.ShellFlyoutRecyclerAdapter.OnBindViewHolder (Android.Support.V7.Widget.RecyclerView/ViewHolder,int) [0x0002a] in D:\a\1\s\Xamarin.Forms.Platform.Android\Renderers\ShellFlyoutRecyclerAdapter.cs:77
  at Android.Support.V7.Widget.RecyclerView/Adapter.n_OnBindViewHolder_Landroid_support_v7_widget_RecyclerView_ViewHolder_I (intptr,intptr,intptr,int) [0x00012] in <844c913cb32f4510879031be59eb1dce>:0
  at (wrapper dynamic-method) Android.Runtime.DynamicMethodNameCounter.63 (intptr,intptr,intptr,int) [0x0001d] in <0623d8432cef4751a77985c521d75c2f>:0
  at (wrapper native-to-managed) Android.Runtime.DynamicMethodNameCounter.63 (intptr,intptr,intptr,int) [0x00035] in <0623d8432cef4751a77985c521d75c2f>:0
  at <unknown> <0xffffffff>
  at (wrapper managed-to-native) Java.Interop.NativeMethods.java_interop_jnienv_call_nonvirtual_void_method_a (intptr,intptr&,intptr,intptr,intptr,intptr) <0x00007>
  at Java.Interop.JniEnvironment/InstanceMethods.CallNonvirtualVoidMethod (Java.Interop.JniObjectReference,Java.Interop.JniObjectReference,Java.Interop.JniMethodInfo,Java.Interop.JniArgumentValue*) [0x00079] in <3ffd030629264cf9a5adda85ea742eb9>:0
  at Java.Interop.JniPeerMembers/JniInstanceMethods.InvokeNonvirtualVoidMethod (string,Java.Interop.IJavaPeerable,Java.Interop.JniArgumentValue*) [0x00021] in <3ffd030629264cf9a5adda85ea742eb9>:0
  at Android.Views.ViewGroup.Layout (int,int,int,int) [0x00069] in <0623d8432cef4751a77985c521d75c2f>:0
  at Xamarin.Forms.Platform.Android.ShellRenderer.OnElementSizeChanged (object,System.EventArgs) [0x00092] in D:\a\1\s\Xamarin.Forms.Platform.Android\Renderers\ShellRenderer.cs:315
  at Xamarin.Forms.VisualElement.SetSize (double,double) [0x00029] in D:\a\1\s\Xamarin.Forms.Core\VisualElement.cs:1047
  at Xamarin.Forms.VisualElement.set_Bounds (Xamarin.Forms.Rectangle) [0x0005d] in D:\a\1\s\Xamarin.Forms.Core\VisualElement.cs:357
  at Xamarin.Forms.VisualElement.Layout (Xamarin.Forms.Rectangle) [0x00000] in D:\a\1\s\Xamarin.Forms.Core\VisualElement.cs:724
  at Xamarin.Forms.Platform.Android.AppCompat.Platform.LayoutRootPage (Xamarin.Forms.Page,int,int) [0x00000] in D:\a\1\s\Xamarin.Forms.Platform.Android\AppCompat\Platform.cs:405
  at Xamarin.Forms.Platform.Android.AppCompat.Platform.Xamarin.Forms.Platform.Android.IPlatformLayout.OnLayout (bool,int,int,int,int) [0x0000c] in D:\a\1\s\Xamarin.Forms.Platform.Android\AppCompat\Platform.cs:232
  at Xamarin.Forms.Platform.Android.PlatformRenderer.OnLayout (bool,int,int,int,int) [0x0001a] in D:\a\1\s\Xamarin.Forms.Platform.Android\PlatformRenderer.cs:75
  at Android.Views.ViewGroup.n_OnLayout_ZIIII (intptr,intptr,bool,int,int,int,int) [0x00010] in <0623d8432cef4751a77985c521d75c2f>:0
  at (wrapper dynamic-method) Android.Runtime.DynamicMethodNameCounter.38 (intptr,intptr,bool,int,int,int,int) [0x0002f] in <0623d8432cef4751a77985c521d75c2f>:0
  at (wrapper native-to-managed) Android.Runtime.DynamicMethodNameCounter.38 (intptr,intptr,int,int,int,int,int) [0x00045] in <0623d8432cef4751a77985c521d75c2f>:0

"Thread Pool Worker"
"Thread Pool Worker"  at <unknown> <0xffffffff>
  at System.Threading._ThreadPoolWaitCallback.PerformWaitCallback () <0x00007>
  at (wrapper runtime-invoke) <Module>.runtime_invoke_bool (object,intptr,intptr,intptr) [0x0002b] in <0381c8f952fb47759ee29160e807b17d>:0

"Finalizer"
"Thread Pool Worker"
"Debugger agent"
"Thread Pool Worker"
"Thread Pool Worker"  at <unknown> <0xffffffff>
  at System.Threading._ThreadPoolWaitCallback.PerformWaitCallback () <0x00007>
  at (wrapper runtime-invoke) <Module>.runtime_invoke_bool (object,intptr,intptr,intptr) [0x0002b] in <0381c8f952fb47759ee29160e807b17d>:0

"<threadpool thread>"
"Thread Pool Worker"09-29 01:00:17.888 D/AppEyeBinderBlock( 1285): read binder transaction end

[redradist]

@chkr1011 I have figured out that hanging up come in Debug mode for Xamarin application, seems like debugger use some thread that with addition with failed connection to broker hanging up

When I run application without debug mode, just tap on icon, it starts properly ...

Also when I add _managedMqttClient.ConnectingFailedHandler than even in Debug mode application works properly after connection is failed ...

[chkr1011]

@redradist What dies "add" the connection failed handler? Do you have also some code in the handler or only attached?

[redradist]

@chkr1011 Seems like this my issue was due to Rider IDE ... On Visual Studio issue is not reproducible

If you interested there is ticket for it https://youtrack.jetbrains.com/issue/RIDER-52622

[chkr1011]

@fdundjer Sorry for the long delay. Is this issue still relevant? I am not sure how to solve this because this library only makes use of sockets. Probably it is required to check availability of network via Xamarin APIs first?

[ReikoLJ]

@fdundjer Sorry for the long delay. Is this issue still relevant? I am not sure how to solve this because this library only makes use of sockets. Probably it is required to check availability of network via Xamarin APIs first?

Though not a Xamarin specific issue, I'm having an issue with the ConnectAsync method just swallowing the thread if the broker is not available at that time. No exception is returned so I cannot handle this behaviour in code. It's a very straight forward setup using node-red as a temp broker. If that node-red broker isn't running the client just hangs forever which is something I definitely don't want when this is turned into production code with a real broker

var factory = new MqttFactory(); _mqttClient = factory.CreateMqttClient();

var options = new MqttClientOptionsBuilder().WithTcpServer("localhost", 1883).Build(); await _mqttClient.ConnectAsync(options);

[kwende]

@ReikoLJ have a look at https://github.com/chkr1011/MQTTnet/pull/1318

[chkr1011]

I assume this issue is fixed. If the issue still exists in the latest version 4 please reopen the ticket and try connecting with apps like MQTTnetApp to see if the library is the root cause of this issue.