System.Net.Security.NegotiateStream.Flush C# (CSharp) Method

        public override void Flush()
        {
#if DEBUG
            using (DebugThreadTracking.SetThreadKind(ThreadKinds.User | ThreadKinds.Sync))
            {
#endif
                InnerStream.Flush();
#if DEBUG
            }
#endif
        }

        /// <summary>
        /// Authenticates the client stream
        /// </summary>
        /// <param name="stream">The stream to autenticate</param>
        /// <param name="userToken">the user token associated with the identity match</param>
        /// <param name="additionalChallenge">Additional data that much match between the client and server
        /// for the connection to succeed.</param>
        /// <returns>true if successful authentication. False otherwise.</returns>
        public bool TryAuthenticateAsServer(Stream stream, out Guid userToken, byte[] additionalChallenge = null)
        {
            userToken = Guid.Empty;
            if (additionalChallenge == null)
                additionalChallenge = new byte[] { };
            if (additionalChallenge.Length > short.MaxValue)
                throw new ArgumentOutOfRangeException("additionalChallenge", "Must be less than 32767 bytes");

            using (var negotiateStream = new NegotiateStream(stream, true))
            {
                try
                {
                    negotiateStream.AuthenticateAsServer(CredentialCache.DefaultNetworkCredentials, ProtectionLevel.EncryptAndSign, TokenImpersonationLevel.Identification);
                }
                catch (Exception ex)
                {
                    Log.Publish(MessageLevel.Info, "Security Login Failed", "Attempting an integrated security login failed", null, ex);
                    return false;
                }

                negotiateStream.Write((short)additionalChallenge.Length);
                if (additionalChallenge.Length > 0)
                {
                    negotiateStream.Write(additionalChallenge);
                }
                negotiateStream.Flush();

                int len = negotiateStream.ReadInt16();
                if (len < 0)
                {
                    Log.Publish(MessageLevel.Info, "Security Login Failed", "Attempting an integrated security login failed", "Challenge Length is invalid: " + len.ToString());
                    return false;
                }

                byte[] remoteChallenge;
                if (len == 0)
                {
                    remoteChallenge = new byte[0];
                }
                else
                {
                    remoteChallenge = negotiateStream.ReadBytes(len);
                }

                if (remoteChallenge.SecureEquals(additionalChallenge))
                {
                    if (Users.TryGetToken(negotiateStream.RemoteIdentity, out userToken))
                    {
                        return true;
                    }
                    Log.Publish(MessageLevel.Info, "Security Login Failed", "Attempting an integrated security login failed", "User did not exist in the database: " + negotiateStream.RemoteIdentity.ToString());
                    return false;
                }

                Log.Publish(MessageLevel.Info, "Security Login Failed", "Attempting an integrated security login failed", "Challenge did not match. Potential man in the middle attack.");
                return false;
            }
        }