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An overview of inetd
The Internet daemon, or inetd, is the master server that coordinates the
use of individual network services on your system. It listens for
connection requests from other nodes on the network who want access to a
service such as tftpd or bootpd. The Internet daemon checks if the
requesting node has permission to use the service, starts the appropriate
server if it does and, optionally, records information about the
connection request.
Stream services
The Internet daemon starts servers for both stream services and datagram
services. For stream services, which use the TCP/IP protocol, inetd
listens for connection requests on stream sockets. When it detects such
a request, inetd determines which service the socket corresponds to and
invokes a server for it. The server then handles incoming data,
providing a reliable, full-duplex bytestream service to the requesting
node. Once inetd has invoked the server, it returns to listening for
other connection requests.
Datagram services
For datagram services, which use the UDP/IP protocol, inetd listens for
requests on datagram sockets. You can think of a datagram as a
connection request and the message all in one package. Unlike the TCP/IP
protocol, UDP/IP does not provide any message acknowledgment, flow
control or sequencing. It is the simplest possible service with the
advantage of low communications overhead. When inetd detects an incoming
datagram, it invokes a server for that message. Once a datagram has been
delivered, the socket becomes available for another incoming datagram.
That is, there is no "connection" per se, simply the delivery and receipt
of the datagram. For this reason, datagram service is sometimes referred
to as "connectionless" communication.
Internal services provided by inetd
The Internet daemon provides several internal trivial services which are
described below.
Service Description
echo Returns a character to the socket that sent it
discard Discards all input from socket
chargen Generates characters and sends them to a socket
daytime Returns the current time in a format readable by
people
time Returns current time in a format useful to
machines, i.e., the number of seconds since Jan 1,
1970
The inetd files
There are four files of importance for configuring and using inetd. Once
you have installed or updated to version C.55.00 of MPE/iX, these files
are located in the NET group of the SYS account.
Table 2-1. The Internet daemon files
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| | |
| File | Description |
| | |
--------------------------------------------------------------------------------------------
| | |
| INETD.NET.SYS | The program file for inetd which is linked to the |
| | POSIX file /etc/inetd. |
| | |
--------------------------------------------------------------------------------------------
| | |
| INCNFSMP.NET.SYS | The sample configuration file for inetd. You will |
| | copy the sample file to INETCONF.NET.SYS, create a |
| | symbolic link from the POSIX file /etc/inetd.conf |
| | to INETDCNF.NET.SYS, and edit it as necessary. |
| | |
--------------------------------------------------------------------------------------------
| | |
| INSECSMP.NET.SYS | The sample security file for inetd. You will copy |
| | this file to INETSEC.NET.SYS, create a symbolic |
| | link from the POSIX file /usr/adm/inetd.sec to |
| | INETSEC.NET.SYS, and edit it as necessary. |
| | |
--------------------------------------------------------------------------------------------
| | |
| JINETD.NET.SYS | The job file that you will stream to start inetd |
| | and abort to stop inetd. You won't need to copy, |
| | link, or edit this file. |
| | |
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The remainder of this chapter explains how to copy, link and edit these
files to create a working version of the Internet daemon on your system.