C# Класс BestHTTP.SecureProtocol.Org.BouncyCastle.Crypto.Tls.TlsNoCloseNotifyException
This exception will be thrown(only) when the connection is closed by the peer without sending a close_notify warning alert.
If this happens, the TLS protocol cannot rule out truncation of the connection data (potentially malicious). It may be possible to check for truncation via some property of a higher level protocol built upon TLS, e.g.the Content-Length header for HTTPS.