Security

A critical aspect of any network application these days is security. 
Stem hubs communicate with each other via standard internet sockets. 
This communication can be made secure by tunneling over existing 
open source products such as SSH and Stunnel.  Stem runs the security 
program and has it connect with the remote hub and its stdin/stdout 
is used for the local connection.  The Stem::Proc cell is used to 
manage this external security program and it provides all the I/O 
support needed.  The Stem::Portal cell is used to connect Stem hubs 
together and it has configuration options to select the desired 
security application and options.  A Stem hub can listen for portal 
connections using a Listen socket bound to localhost or an IP 
address.  By using localhost and a secure transport, a Stem hub 
cannot be accessed by any unauthorized programs.