How would you implement a standard event-detection system based on server-client communication on a Linux machine that r

[answerhappygod]

How would you implement a standard event-detection system based
on server-client communication on a Linux machine that runs a
program to alert a remote client? There does not need to be any
code written, just good explanation. Please discuss how, with and
without a web server on the machine. You can assume that the
machine runs standard Linux, FTP, SSH, etc. and is in any language
you prefer, but do not assume existence of any special
environments like Express etc.