A Tunnel can be configured to Disconnect in a number of ways:

Disabled: never disconnected

Timeout: disconnect after idle timeout occurs

Stop Character: disconnect when the Stop Character is read on the Serial Line

Modem Control Not Asserted: disconnect when Modem Control pin is not asserted on the Serial Line

The Timeout specifies the idle time on a connection that must pass before a Tunnel is disconnected.

The Flush Serial Data boolean specifies to flush the Serial Line when the Tunnel is disconnected.