Is there a method I can call to close all the sql server connections.

I'm trying to give the application a way for the user to disconnect from the server (close child windows and cisco vpn) and login again later (open vpn) without closing the main app.  All is working except for when I try to login for the second time.  I'm getting a SqlException: A transport-level error has occurred when sending the request to the server. (provider: TCP Provider, error:0 - An existing connection was forcibly closed by the remote host).  Could this be caused by the sql connection not being close prior to the vpn shutting down?  Is there a way to close connections?

Thanks!