Error message on server side with websocket

Hi all,

I connected arduino to websocket server successfuly but I get this error on server log, what is it ?
Html page connected to same websocket with no error, only from Arduino.

System.Net.WebSockets.WebSocketException (0x800703E3): The I/O operation has been aborted because of either a thread exit or an application request
at System.Web.WebSockets.WebSocketPipe.<>c__DisplayClass7.b__6(Int32 hrError, Int32 cbIO, Boolean fUtf8Encoded, Boolean fFinalFragment, Boolean fClose)
— End of stack trace from previous location where exception was thrown —
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at System.Web.WebSockets.AspNetWebSocket.d__2d`1.MoveNext()
— End of stack trace from previous location where exception was thrown —
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at System.Web.WebSockets.AspNetWebSocket.<>c__DisplayClass1a.<b__18>d__1c.MoveNext()
— End of stack trace from previous location where exception was thrown —
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Microsoft.Web.WebSockets.WebSocketMessageReader.d__0.MoveNext()
— End of stack trace from previous location where exception was thrown —
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Microsoft.Web.WebSockets.WebSocketHandler.d__9.MoveNext()