Administering a Unix Server

What inetd Does
Setting up inetd
Defining the server


The installation routine for Cobol-RPC Cobol performs all necessary Unix configuration automatically. This section describes that configuration information so that you can change it manually should the need arise.

Before Cobol-RPC can execute remote program calls, a process must be created that will listen for requests. This process, inetd, is a standard part of the Unix operating system. It provides this functionality for features like ftp and finger. It will also provide it for Cobol-RPC. We just need to add a line to its configuration file.

What inetd Does

inetd listens for connections on a number of ports. Each port is related to a service such as ftp or Cobol-RPC. When inetd senses a connection, it determines which service it is associated with and starts the process related to that service. The inetd.conf file lists the services inetd should listen for and tells it what process to start for each service.

Setting up inetd

inetd is configured by editing the contents of inetd.conf. This file is generally located in the /etc directory. The installation of Cobol-RPC adds a line to this file. It looks like this:

cobolrpc stream tcp nowait root /bin/sh /bin/sh /cobolrpc/rpcstart

Here's a description of each component:

The first item, cobolrpc, is the name of the service inetd is supposed to listen for. This service must be described in /etc/services. We will get to that later. You should not need to change this.

The next three items, stream tcp nowait, described the type of network communication needed. Do not change these options.

The next item, root, indicates the user that the server process will be initiated for. You may want to have your remote program calls executed under a different user name. Just be certain that the user name used here has adequate permissions to find and execute remote programs.

The next entry, /bin/sh, is the name of the program inetd should initiate for the service. /bin/sh is specified because a shell script is used to start Cobol-RPC. This entry is repeated and should not be changed.

The last item, /cobolrpc/rpcstart, is a shell script that starts the Cobol runtime system. The rpcstart script can be edited to set additional environment variables required by the Cobol application.

Note that the Cobol runtime system must be started in a "quiet" mode that does not display information on the screen. A banner display by the runtime would corrupt network communications.

Defining the server

Remember the service name that was included as the first element in the inetd.conf entry, cobolrpc. When Cobol-RPC was installed, the following line was added to the /etc/services file to define that service:

cobolrpc 5000/tcp

This defines cobolrpc as a service using tcp protocol on portPort 5000. Do not change the service name or protocol. You can, however, select a different port number. Just be certain that the port number you select is not used by any other service on the server and matches the port number used by the Cobol-RPC clients.

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