|
|
|
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," 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 here.
- 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, for example, the
number of seconds since Jan 1, 1970.
inetd Files
There are four files of importance as shown in
Table 2-1 "The Internet Daemon Files" for
configuring and using inetd. Once you have installed or updated to
version C.60.00 or later, of MPE/iX, these files are located in the
NET group of the SYS account.
Table 2-1 The Internet Daemon Files
| 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 INETDCNF.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
INETDSEC.NET.SYS, create a symbolic link from the POSIX file
/usr/adm/inetd.sec to INETDSEC.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. |
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.
|
