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