Closed Connection - Reason: An exception has occurred while connecting.

i am using websocket sharp in unity and in the server side i use SignalR, it's ok and everything works well but my problem is sometimes when i start to connect, the websocket sharp cause this error: "Closed Connection - An exception has occurred while connecting" and after that everytime i start application the error displaying again.
the websocket logger is:

8/21/2018 4:43:42 PM|Warn |Logger.set_File:0|The current path to the log file has been changed to websocket.log.
8/21/2018 4:43:42 PM|Debug|WebSocket.sendHttpRequest:0|A request to the server:
GET /signalr/connect?transport=webSockets&connectionToken=J4miXlCpKRgShrRbd8GK1au%2B6k7UYtBHV%2Fg2kRwG6iUh3yofmoKesO0Qm%2FwGnlfU700ieOENOeUEaGJOFYAQAFrS0lASreArieqM7XPOQmzeKIW4Dx2Rqc%2Fo05ZB9ztWcwWYErDRrlp30S0UNkDbxQ%3D%3D&connectionData=%5B%7B%22name%22%3A%22game%22%7D%5D&tid=8&authorization=Bearer%20eyJhbGciOiJodHRwOi8vd3d3LnczLm9yZy8yMDAxLzA0L3htbGRzaWctbW9yZSNobWFjLXNoYTI1NiIsInR5cCI6IkpXVCJ9.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.JYrsm48lwICMOMzY9MNwjgtBMGTPZcGbyrp-VwDBeJs HTTP/1.1
User-Agent: websocket-sharp/1.0
Host: artstorm.ir
Upgrade: websocket
Connection: Upgrade
Sec-WebSocket-Key: c4g6LyAgEC9Z5loohIw5Vg==
Sec-WebSocket-Version: 13
8/21/2018 4:43:42 PM|Debug|WebSocket.sendHttpRequest:0|A response to this request:
HTTP/1.1 101 Switching Protocols
Upgrade: websocket
Server: Microsoft-IIS/10.0
X-Content-Type-Options: nosniff
Sec-WebSocket-Accept: DL56iuslEBzQrI8///p+uZVwm/Y=
Connection: Upgrade
X-Powered-By: ASP.NET
Date: Tue, 21 Aug 2018 12:14:22 GMT
8/21/2018 4:44:12 PM|Fatal|WebSocket.b__176_2:0|WebSocketSharp.WebSocketException: The header of a frame cannot be read from the stream.
at WebSocketSharp.WebSocketFrame.processHeader (System.Byte[] header) [0x00000] in :0
at WebSocketSharp.WebSocketFrame+<>c__DisplayClass73_0.b__0 (System.Byte[] bytes) [0x00000] in :0
at WebSocketSharp.Ext+<>c__DisplayClass50_0.b__0 (IAsyncResult ar) [0x00000] in :0
8/21/2018 4:44:12 PM|Debug|WebSocket.closeHandshake:0|Was clean?: False
sent: False
received: False

Start with the reported WebSocketFrame.processHeader, readHeaderAsync, and startReceiving stack-trace entries, then compare them with the logged HTTP 101 response and subsequent frame-read failure. Reproduce the Unity client connection against the SignalR server and determine the conditions that lead to the closed connection; document the cause and a reliable verification case.