write replacements

[Jyrki Kuoppala]

In article <kre.673344580 at mundamutti.cs.mu.OZ.AU>, kre at cs (Robert Elz) writes:
[ describes a zephyr-like / write-like system on which you can control
  the appearance of the arriving message ]

I did something like that when getting familiar with SunRPC.  It's a
bit buggy, but the idea is basically the one you're after, I think.
Also, it appears that SunRPC is not very good for this so the program
should be rewritten to work on top of a tcp protocol (funny, when it
was just an exercise in SunRPC to start with ;-).

Here's the README file; the package is in nic.funet.fi,
pub/unix/tcpip/rmsg.tar.Z.  If anyone is willing to adopt it and make
it better, feel free.

This directory contains a messaging system which can be used to send
write-like messages to logged-on users.  The system can cross machine
boundaries, so if another machine has the rmsgd program running, you can
send messages to users on it.

The system also allows bitnet virtual machine-like 'virtual users'
to whom any user can send messages and they can answer the messages.
The rmsgd server makes this possible by allowing a command 'exec' in a users
.msgconf file, and whenever the user receives a message this command is
executed and the message is piped to it.

It is also possible to log incoming and outgoing messages and resend previous
sent message.  You can specify a file to which the last (or every) incoming
message will be stored.

Using the programs:
-------------------

Rmsgd:

Rmsgd is the server program for the system.  It should be started by root,
but for now it works even if started by ordinary users, even though
some capabilities are disabled for security reasons (that is, exec and 
logging of incoming messages, since that would be done by the user-id
who started rmsgd and not the receiver).

At any time, there should be only one rmsgd running.  It doesn't do any harm
to have several rmsgds other than the newly-started servers unmap the
previous and thus the previous servers are unusable.

The server should be named 'rmsgd' to have it start as a daemon.


Rmsg:

Rmsg is the client end of the system.  Rmsg is used by ordinary users
to send messages.  For example, rmsg foo at bar hello there !  ^D would
send a message 'hello there !' to user foo at machine bar.  By
default, rmsg stores the last outgoing message in the user's home
directory in the file .msgout.  Then msg -r user at machine can be used
to resend the message.  Message is normally read from standard input
until EOF.

Configuration:
--------------

The messages system has many options which the user can set by making
a file '.msgconf' in her home directory and placing various command in it.
Read the manual page for rmsg for more information.


//Jyrki