Network Programming with Perl

Handling HUP and Other Signals

It is often necessary to reconfigure a server that is already running. Many UNIX daemons follow a convention in which the HUP signal is treated as a command to reinitialize or reset the server. For example, a server that depends on a configuration file might respond to the HUP signal by reparsing the file and reconfiguring itself. HUP was chosen because it is not normally received by a process that has detached itself from the controlling terminal.

As a last iteration of the psychotherapist server, we will rewrite it to respond to the HUP signal by terminating all its current connections, closing the listen socket, and then relaunching itself. We will also modify the TERM handler so that the server terminates all ...