[stunnel-users] How to tell if commuications are encrypted?

Hello, I have Stunnel installed on Windows Server 2008 R2, running as a service. I have it installed as a client on a Windows POS 2009 device. This setup is working, in that the client is operating correctly and using Stunnel. But how can I tell if communications between the Stunnel client and the Stunnel server are being encrypted, rather than Stunnel just doing port forwarding? I did read the client needs to have access to the server's certificate, but at the moment it does not. Alex