3.14.4 From (Unix) inetd
All modern Unix systems handle a large number of the services they
run through the super-server inetd. This program reads
/etc/inetd.conf and opens server-sockets on all ports
defined in this file. As a request comes in it accepts it and starts the
associated server such that standard I/O refers to the socket. This
approach has several advantages:
- Simplification of servers
Servers don't have to know about sockets and -operations. - Centralised authorisation
Using tcpwrappers simple and effective firewalling of all services is realised. - Automatic start and monitor
The inetd automatically starts the server‘just-in-time' and starts additional servers or restarts a crashed server according to the specifications.
The very small generic script for handling inetd based connections is
in inetd_httpd, defining http_server/1:
- http_server(:Goal, +Options)
- Initialises and runs http_wrapper/5 in a loop until failure or end-of-file. This server does not support the Port option as the port is specified with the inetd configuration. The only supported option is After.
Here is the example from demo_inetd
#!/usr/bin/pl -t main -q -f
:- use_module(demo_body).
:- use_module(inetd_httpd).
main :-
http_server(reply).
With the above file installed in /home/jan/plhttp/demo_inetd,
the following line in /etc/inetd enables the server at port
4001 guarded by tcpwrappers. After modifying inetd, send the
daemon the HUP signal to make it reload its configuration.
For more information, please check inetd.conf(5).
4001 stream tcp nowait nobody /usr/sbin/tcpd /home/jan/plhttp/demo_inetd