stale VNC session persists in server

I have for unknown reasons a VNC session still connected to Vine Server 3.0 (1016). Any time I create a new session under this circumstance I have to make sure I ask for a shared connection. I wonder if there’s a way to implement an “are you alive” message between the Vine Server and its clients so stale VNC sessions could be found and eliminated.

Here is a RealVNC 4.1.2 session to my Mac showing my Vine Server window showing two active sessions on display :1 when there should only be one.