WinRT WebSocket throws unhandled exception on lost connection

[arturl]

The issues affects UWP implementation of ClientWebSocket.

When ReceiveAsync call is pending and the connection is lost, System.Net.WebSockets.WinRTWebSocket.OnMessageReceived throws an exception with HRESULT 0x80072EFE ("The connection with the server was terminated abnormally") here:
https://github.com/dotnet/corefx/blob/master/src/System.Net.WebSockets.Client/src/System/Net/WebSockets/WinRTWebSocket.cs#L282

The exception is thrown on a background thread, which cannot be handled so it brings down the process.

[davidsh]

Added information from @arturl

I’m not familiar with .NET Core versioning. I’m using Microsoft.NETCore.UniversalWindowsPlatform 5.2.2 package. I think these are the relevant assemblies:
 
                System.Net.WebSockets.Client.dll          D:\g\azure-iot-sdk-csharp\device\samples\UWPSample\bin\x86\Debug\AppX\System.Net.WebSockets.Client.dll     No          N/A                Symbols loaded. c:\symbols\System.Net.WebSockets.Client.pdb\4d9fc6dcf0c5490c8a7109492ef110e71\System.Net.WebSockets.Client.pdb                27           4.06.24705.1       11/4/2016 21:38               0FF60000-0FF70000         [10104] UWPSample.exe              [1] CoreCLR_UWP_Domain 
                System.Net.WebSockets.dll       D:\g\azure-iot-sdk-csharp\device\samples\UWPSample\bin\x86\Debug\AppX\System.Net.WebSockets.dll  No          N/A        Symbols loaded. c:\symbols\System.Net.WebSockets.pdb\fc82556df289488cbf50c6cf0c092e601\System.Net.WebSockets.pdb                28           4.06.24705.1       11/4/2016 21:38               0FF70000-0FF7A000        [10104] UWPSample.exe              [1] CoreCLR_UWP_Domain 
 
The exception happens in WinRTWebSocket.OnMessageReceived (not my code) on a thread that I cannot control. I cannot redirect it to my own callback.

[arturl]

More info - exception and partial call stack here:

                                e             {Windows.UI.Xaml.UnhandledExceptionEventArgs}                Windows.UI.Xaml.UnhandledExceptionEventArgs
-                              Exception            {System.Exception: Exception from HRESULT: 0x80072EFE
   at Windows.Networking.Sockets.MessageWebSocketMessageReceivedEventArgs.GetDataReader()
   at System.Net.WebSockets.WinRTWebSocket.OnMessageReceived(MessageWebSocket sender, MessageWebSocketMessageReceivedEventArgs args)}   System.Exception
+                             Data       {System.Collections.ListDictionaryInternal}          System.Collections.IDictionary {System.Collections.ListDictionaryInternal}
                                HResult -2147012866       int
                                HelpLink               null         string
-                              InnerException null         System.Exception
+                             Static members                
                                Message              "Exception from HRESULT: 0x80072EFE" string
                                Source  "Windows"         string
                                StackTrace          "   at Windows.Networking.Sockets.MessageWebSocketMessageReceivedEventArgs.GetDataReader()\r\n   at System.Net.WebSockets.WinRTWebSocket.OnMessageReceived(MessageWebSocket sender, MessageWebSocketMessageReceivedEventArgs args)"   string
-                              Non-Public members                     
                                _COMPlusExceptionCode             -532462766         int
                                s_EDILock            {object} object
+                             Non-Public members                     
                                Handled               false      bool
                                Message              "System.Exception: Exception from HRESULT: 0x80072EFE\r\n   at Windows.Networking.Sockets.MessageWebSocketMessageReceivedEventArgs.GetDataReader()\r\n   at System.Net.WebSockets.WinRTWebSocket.OnMessageReceived(MessageWebSocket sender, MessageWebSocketMessageReceivedEventArgs args)"   string

[Trolldemorted]

I can confirm this is happening, same stacktrace:

   at Windows.Networking.Sockets.MessageWebSocketMessageReceivedEventArgs.GetDataReader()
   at System.Net.WebSockets.WinRTWebSocket.OnMessageReceived(MessageWebSocket sender, MessageWebSocketMessageReceivedEventArgs args)

Is there a workaround for this, or will we have to wait for a new release of System.Net.WebSockets.Client?

[davidsh]

Is there a workaround for this, or will we have to wait for a new release of System.Net.WebSockets.Client?

I don't think there is a workaround. The exception is happening in internal code and is leaking which crashes the process.

[Trolldemorted]

Are dirty hacks like catching every unhandled exception within the app and ignoring it impossible?

And out of curiosity, why is this only happening on UWP?

[davidsh]

Are dirty hacks like catching every unhandled exception within the app and ignoring it impossible?

Unlikely to help. The exception is leaking out of internal code on a threadpool thread. It will crash the process. It might be possible for your app to install a special "unhandled exception" handler. But I'm not really familiar with that.

And out of curiosity, why is this only happening on UWP?

The UWP version of System.Net.WebSockets.Client is different from non-UWP. It uses different source code in the implementation (very different). Currently it uses the WinRT WebSockets APIs as the underlying implementation. This is very different from the non-UWP binaries in the System.Net.WebSockets.Client package.

[Trolldemorted]

Damn.

I suppose it will continue to use WinRT WebSockets until .netstandard2.0 is coming? Can you estimate when a fix for this will be available? Unfortunately System.Net.WebSockets.Client is the only option in .netstandard libraries, leading to every uwp app that uses a netstandard library that uses websockets being killed if a server closes a websocket connection.

[davidsh]

cc: @karelz

I have no estimate at this time. Any short-term fix would have to done via the release/servicing branches (such as release/1.1.0 etc.) and then a new updated System.Net.WebSockets.Client nuget package generated (tested and marked as stable).

We will hopefully post an update on schedule expectations within the next week or so.

[moozzyk]

SignalR is hitting this as well: aspnet/SignalR#412

[karelz]

@moozzyk this is UWP (client) issue, not .NET Core. How is this affecting SignalR? I thought that is server-side scenario. What is the scenario? How common is it?

[moozzyk]

SignalR consists of the server and the client. The server runs on .NET core but the C# client targets netstandard1.3 so that it can run all over the place (desktop, .NET Core, xamarin, UWP etc.). WebSockets is the default transport so the bug can be hit easily when running SignalR client in a UWP app.

[caesar-chen]

Should we triage this issues as "System.Net"? Since it's related to WebSockets.

@davidsh @CIPop

[alekkowalczyk]

Any news on that issue? Some expected timeframe for a new version of the websockets package with a fix?