private async Task <AmqpSession> CreateSessionAsync(TimeSpan timeout)
        {
            Logging.Enter(this, timeout, nameof(CreateSessionAsync));

            TransportBase transport = null;

            try
            {
                var timeoutHelper = new TimeoutHelper(timeout);
                _refreshTokenTimer.Cancel();

                AmqpSettings amqpSettings = CreateAmqpSettings();
                if (_useWebSocketOnly)
                {
                    // Try only AMQP transport over WebSocket
                    transport = _clientWebSocketTransport = (ClientWebSocketTransport) await CreateClientWebSocketTransportAsync(timeoutHelper.RemainingTime())
                                                            .ConfigureAwait(false);
                }
                else
                {
                    TlsTransportSettings tlsTransportSettings = CreateTlsTransportSettings();
                    var amqpTransportInitiator = new AmqpTransportInitiator(amqpSettings, tlsTransportSettings);
                    try
                    {
                        transport = await amqpTransportInitiator.ConnectTaskAsync(timeoutHelper.RemainingTime()).ConfigureAwait(false);
                    }
                    catch (Exception e) when(!(e is AuthenticationException))
                    {
                        Logging.Error(this, e, nameof(CreateSessionAsync));

                        if (Fx.IsFatal(e))
                        {
                            throw;
                        }

                        // AMQP transport over TCP failed. Retry AMQP transport over WebSocket
                        if (timeoutHelper.RemainingTime() != TimeSpan.Zero)
                        {
                            transport = _clientWebSocketTransport = (ClientWebSocketTransport) await CreateClientWebSocketTransportAsync(timeoutHelper.RemainingTime()).ConfigureAwait(false);
                        }
                        else
                        {
                            throw;
                        }
                    }
                }

                Logging.Info(this, $"Initialized {nameof(TransportBase)}, ws={_useWebSocketOnly}");

                var amqpConnectionSettings = new AmqpConnectionSettings
                {
                    MaxFrameSize = AmqpConstants.DefaultMaxFrameSize,
                    ContainerId  = Guid.NewGuid().ToString("N", CultureInfo.InvariantCulture), // Use a human readable link name to help with debugging
                    HostName     = ConnectionString.AmqpEndpoint.Host,
                };

                var amqpConnection = new AmqpConnection(transport, amqpSettings, amqpConnectionSettings);
                await amqpConnection.OpenAsync(timeoutHelper.RemainingTime()).ConfigureAwait(false);

                Logging.Info(this, $"{nameof(AmqpConnection)} opened.");

                var sessionSettings = new AmqpSessionSettings
                {
                    Properties = new Fields(),
                };

                try
                {
                    AmqpSession amqpSession = amqpConnection.CreateSession(sessionSettings);
                    await amqpSession.OpenAsync(timeoutHelper.RemainingTime()).ConfigureAwait(false);

                    Logging.Info(this, $"{nameof(AmqpSession)} opened.");

                    // This adds itself to amqpConnection.Extensions
                    var cbsLink = new AmqpCbsLink(amqpConnection);
                    await SendCbsTokenAsync(cbsLink, timeoutHelper.RemainingTime()).ConfigureAwait(false);

                    return(amqpSession);
                }
                catch (Exception ex) when(!ex.IsFatal())
                {
                    Logging.Error(this, ex, nameof(CreateSessionAsync));

                    _clientWebSocketTransport?.Dispose();
                    _clientWebSocketTransport = null;

                    if (amqpConnection.TerminalException != null)
                    {
                        throw AmqpClientHelper.ToIotHubClientContract(amqpConnection.TerminalException);
                    }

                    amqpConnection.SafeClose(ex);
                    throw;
                }
            }
            finally
            {
                Logging.Exit(this, timeout, nameof(CreateSessionAsync));
            }
        }
        private async Task <AmqpSession> CreateSessionAsync(TimeSpan timeout)
        {
            var timeoutHelper = new TimeoutHelper(timeout);

            _refreshTokenTimer.Cancel();

            AmqpSettings  amqpSettings = CreateAmqpSettings();
            TransportBase transport;

            if (_useWebSocketOnly)
            {
                // Try only Amqp transport over WebSocket
                transport = await CreateClientWebSocketTransport(timeoutHelper.RemainingTime()).ConfigureAwait(false);
            }
            else
            {
                TlsTransportSettings tlsTransportSettings = CreateTlsTransportSettings();
                var amqpTransportInitiator = new AmqpTransportInitiator(amqpSettings, tlsTransportSettings);
                try
                {
                    transport = await amqpTransportInitiator.ConnectTaskAsync(timeoutHelper.RemainingTime()).ConfigureAwait(false);
                }
#if !NETSTANDARD1_3
                catch (AuthenticationException)
                {
                    throw;
                }
#endif
                catch (Exception e)
                {
                    if (Fx.IsFatal(e))
                    {
                        throw;
                    }

                    // Amqp transport over TCP failed. Retry Amqp transport over WebSocket
                    if (timeoutHelper.RemainingTime() != TimeSpan.Zero)
                    {
                        transport = await CreateClientWebSocketTransport(timeoutHelper.RemainingTime()).ConfigureAwait(false);
                    }
                    else
                    {
                        throw;
                    }
                }
            }

            var amqpConnectionSettings = new AmqpConnectionSettings
            {
                MaxFrameSize = AmqpConstants.DefaultMaxFrameSize,
                ContainerId  = Guid.NewGuid()
#if NETSTANDARD1_3
                               .ToString("N"),
#else
                               .ToString("N", CultureInfo.InvariantCulture), // Use a human readable link name to help with debugging
#endif
                HostName = ConnectionString.AmqpEndpoint.Host,
            };

            var amqpConnection = new AmqpConnection(transport, amqpSettings, amqpConnectionSettings);
            await amqpConnection.OpenAsync(timeoutHelper.RemainingTime()).ConfigureAwait(false);

            var sessionSettings = new AmqpSessionSettings
            {
                Properties = new Fields(),
            };

            try
            {
                AmqpSession amqpSession = amqpConnection.CreateSession(sessionSettings);
                await amqpSession.OpenAsync(timeoutHelper.RemainingTime()).ConfigureAwait(false);

                // This adds itself to amqpConnection.Extensions
                var cbsLink = new AmqpCbsLink(amqpConnection);
                await SendCbsTokenAsync(cbsLink, timeoutHelper.RemainingTime()).ConfigureAwait(false);

                return(amqpSession);
            }
            catch (Exception ex) when(!ex.IsFatal())
            {
                if (amqpConnection.TerminalException != null)
                {
                    throw AmqpClientHelper.ToIotHubClientContract(amqpConnection.TerminalException);
                }

                amqpConnection.SafeClose(ex);
                throw;
            }
        }