SSL overview
The Secure Sockets Layer (SSL) protocol creates a standard SSL connection between the client and the server. The client contacts the server and checks to make sure that the server has a valid certificate. This type of connection ensures that all data exchanged between client and server is encrypted, and is therefore not readable by a third party on the Internet.
Stunnel is a program that enables encrypting arbitrary TCP connections inside SSL and is available on both UNIX and Windows operating systems. With Stunnel you can secure non-SSL aware daemons and protocols by providing the encryption that requires no changes to the daemon code.