Configuring and Managing MPE/iX Internet Services (August 2002)

Chapter 2
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2 Internet Daemon
The Internet daemon inetd is the master server (sometimes called a “superserver”) for the Internet
Services. When it is running, inetd listens for connection requests for the services listed in its configuration
file and, in response to such requests, starts the appropriate server. You, as system manager, determine which
Internet Services are available to your users by editing the inetd configuration file.
This chapter explains:
• How inetd behaves with stream services and with datagram services.
• How to edit the inetd configuration file so that it listens for connection requests from the specific
Internet Services you want to use on your system.
• How to edit the optional security file for inetd which lets you control access to the Internet Services.
• How to use inetd logging capabilities to monitor and troubleshoot Internet Services.
• How to start and stop inetd.
• How to troubleshoot common problems that can occur with inetd.
• The implementation differences between inetd for MPE/iX and HP-UX.
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,” simply the delivery and
receipt of the datagram. For this reason, datagram service is sometimes referred to as “connectionless”
communication.