Calling websocket.close() from client, causes server to crash[Fatal signal 6 (SIGABRT)]

[durgacharanb]

I have posted the issue @ Olivine-Labs/Alchemy-Websockets-Example#2 .
But looks like that is not the right thread. Posting it here.

I have websocket client running in Safari in iPad(iOS v7.1.2) which tries to disconnect itself from server by calling websocket.close(). On server side I get unhandled exception and application crashes.

Unhandled Exception:
06-23 16:01:58.723 E/mono ( 5122): System.ArgumentException: Buffer is empty
06-23 16:01:58.723 E/mono ( 5122): Parameter name: buffers
06-23 16:01:58.723 E/mono ( 5122): at System.Net.Sockets.Socket.Send (IList1 buffers, SocketFlags socketFlags, System.Net.Sockets.SocketError& errorCode) [0x00000] in <filename unknown>:0 06-23 16:01:58.723 E/mono ( 5122): at System.Net.Sockets.Socket.Send (IList1 buffers, SocketFlags socketFlags) [0x00000] in :0
06-23 16:01:58.723 E/mono ( 5122): at System.Net.Sockets.Socket+Worker.SendGeneric () [0x00000] in :0
06-23 16:01:58.748 F/ ( 5122): * Assertion at /Users/builder/data/lanes/monodroid-mlion-monodroid-4.20-series/ba9bbbdd/source/mono/mono/io-layer/wthreads.c:93, condition `ok' not met

---

Further more if I look at the stack trace, error is thrown while simaphore is tried to release in ReceiveEventArgs_Completed event handler under else condition. Sample code below.

if (context.ReceivedByteCount > 0)
{
context.Handler.HandleRequest(context);
context.ReceiveReady.Release();
StartReceive(context);
}
else
{
context.Disconnect();
context.ReceiveReady.Release();
}

---

Stack Trace

16:01:58.748 E/mono-rt ( 5122): Stacktrace:
06-23 16:01:58.748 E/mono-rt ( 5122):
06-23 16:01:58.748 E/mono-rt ( 5122): at <0xffffffff>
06-23 16:01:58.748 E/mono-rt ( 5122): at (wrapper managed-to-native) System.Threading.NativeEventCalls.SetEvent_internal (intptr) <IL 0x00021, 0xffffffff>
06-23 16:01:58.748 F/libc ( 5122): Fatal signal 6 (SIGABRT) at 0x00001402 (code=-6), thread 5185 (xxxxpackage.namexxx) 06-23 16:01:58.748 E/mono-rt ( 5122): at System.Threading.EventWaitHandle.Set () <IL 0x00018, 0x000fb>
06-23 16:01:58.748 E/mono-rt ( 5122): at (wrapper remoting-invoke-with-check) System.Threading.EventWaitHandle.Set () <IL 0x00038, 0xffffffff>
06-23 16:01:58.748 E/mono-rt ( 5122): at System.Threading.SemaphoreSlim.Release (int) <IL 0x0005f, 0x001d7>
06-23 16:01:58.753 E/mono-rt ( 5122): at System.Threading.SemaphoreSlim.Release () <IL 0x00002, 0x00067>
06-23 16:01:58.753 E/mono-rt ( 5122): at Alchemy.WebSocketServer.ReceiveEventArgs_Completed (object,System.Net.Sockets.SocketAsyncEventArgs) [0x00077] in c:\Alchemy-Websockets-NetCookies\Alchemy-Websockets-NetCookies-master\src\Alchemy.NetCookies.Android\WebSocketServer.cs:331
06-23 16:01:58.753 F/ ( 5122): * Assertion at /Users/builder/data/lanes/monodroid-mlion-monodroid-4.20-series/ba9bbbdd/source/mono/mono/io-layer/wthreads.c:93, conditionok' not met
06-23 16:01:58.753 F/libc ( 5122): Fatal signal 6 (SIGABRT) at 0x00001402 (code=-6), thread 5222 (xxxxpackage.namexxx)
06-23 16:01:58.753 F/ ( 5122): * Assertion at /Users/builder/data/lanes/monodroid-mlion-monodroid-4.20-series/ba9bbbdd/source/mono/mono/io-layer/wthreads.c:93, condition ok' not met
06-23 16:01:58.753 F/ ( 5122): * Assertion at /Users/builder/data/lanes/monodroid-mlion-monodroid-4.20-series/ba9bbbdd/source/mono/mono/io-layer/wthreads.c:93, conditionok' not met
06-23 16:01:58.753 F/libc ( 5122): Fatal signal 6 (SIGABRT) at 0x00001402 (code=-6), thread 5241 (xxxxpackage.namexxx)
06-23 16:01:58.753 F/libc ( 5122): Fatal signal 6 (SIGABRT) at 0x00001402 (code=-6), thread 5221 (xxxxpackage.namexxx)
06-23 16:01:58.753 F/ ( 5122): * Assertion at /Users/builder/data/lanes/monodroid-mlion-monodroid-4.20-series/ba9bbbdd/source/mono/mono/io-layer/wthreads.c:93, condition ok' not met
06-23 16:01:58.753 F/ ( 5122): * Assertion at /Users/builder/data/lanes/monodroid-mlion-monodroid-4.20-series/ba9bbbdd/source/mono/mono/io-layer/wthreads.c:93, conditionok' not met
06-23 16:01:58.753 F/ ( 5122): * Assertion at /Users/builder/data/lanes/monodroid-mlion-monodroid-4.20-series/ba9bbbdd/source/mono/mono/io-layer/wthreads.c:93, condition ok' not met
06-23 16:01:58.753 F/ ( 5122): * Assertion at /Users/builder/data/lanes/monodroid-mlion-monodroid-4.20-series/ba9bbbdd/source/mono/mono/io-layer/wthreads.c:93, conditionok' not met
06-23 16:01:58.753 F/libc ( 5122): Fatal signal 6 (SIGABRT) at 0x00001402 (code=-6), thread 5240 (xxxxpackage.namexxx)
06-23 16:01:58.753 F/ ( 5122): * Assertion at /Users/builder/data/lanes/monodroid-mlion-monodroid-4.20-series/ba9bbbdd/source/mono/mono/io-layer/wthreads.c:93, condition ok' not met
06-23 16:01:58.753 F/libc ( 5122): Fatal signal 6 (SIGABRT) at 0x00001402 (code=-6), thread 5245 (xxxxpackage.namexxx) 06-23 16:01:58.753 F/ ( 5122): * Assertion at /Users/builder/data/lanes/monodroid-mlion-monodroid-4.20-series/ba9bbbdd/source/mono/mono/io-layer/wthreads.c:93, conditionok' not met
06-23 16:01:58.753 F/libc ( 5122): Fatal signal 6 (SIGABRT) at 0x00001402 (code=-6), thread 5248 (xxxxpackage.namexxx)
06-23 16:01:58.753 E/mono-rt ( 5122): at System.Net.Sockets.SocketAsyncEventArgs.OnCompleted (System.Net.Sockets.SocketAsyncEventArgs)
06-23 16:01:58.753 F/libc ( 5122): Fatal signal 6 (SIGABRT) at 0x00001402 (code=-6), thread 5242 (xxxxpackage.namexxx)
06-23 16:01:58.753 F/libc ( 5122): Fatal signal 6 (SIGABRT) at 0x00001402 (code=-6), thread 5246 (xxxxpackage.namexxx)
06-23 16:01:58.753 E/mono-rt ( 5122): at System.Net.Sockets.SocketAsyncEventArgs.ReceiveCallback (System.IAsyncResult)
06-23 16:01:58.753 E/mono-rt ( 5122): at System.Net.Sockets.SocketAsyncEventArgs.DispatcherCB (System.IAsyncResult)
06-23 16:01:58.753 E/mono-rt ( 5122): at (wrapper runtime-invoke) .runtime_invoke_void__this___object (object,intptr,intptr,intptr)
06-23 16:01:58.753 E/mono-rt ( 5122):
06-23 16:01:58.753 E/mono-rt ( 5122): =================================================================
06-23 16:01:58.753 E/mono-rt ( 5122): Got a SIGSEGV while executing native code. This usually indicates
06-23 16:01:58.753 E/mono-rt ( 5122): a fatal error in the mono runtime or one of the native libraries
06-23 16:01:58.753 E/mono-rt ( 5122): used by your application.
06-23 16:01:58.753 E/mono-rt ( 5122): =================================================================

I am not sure if the way I am handling is not right. Is there any workaround or fix, plz let me know.