Can a user \"prod\" a remote host?

[Will Martin -- AMXAL-RI]

Is there any way that an ordinary user can "prod" or signal a remote host
across the ARPA/MILNET to cause that remote host to check for and start
the sending process for mail that may be queued up for delivery to the
user's host?

An example: my host has had problems for some days, such as the network
connection being down, or the machine being down -- something that has
prevented it from receiving mail from the network. It comes back up,
and some incoming mail is delivered. I, as a user on that machine, look
at the mail and can tell that there is still some missing (such as some
mailing-list digests, where issues are numbered and I can see that I have
not received certain numbers). Is there something I can do using the
"telnet" or "ftp" capability to reach across the network to the host
that sends out these messages and tell it that it should now search its
out-bound queues for any mail to my host and start the regular mail delivery
process?

This could be especially valuable if I knew, for example, that my host
will be up for a short time and will then go down again, and that the remote
machine normally delivers mail to us at night when I know that my computer
will be down again. So if I could trigger an unscheduled, right-now mail
delivery, the traffic would get through -- if I do nothing, and let the
scheduled processes run things, there would be another unsucessful
delivery attempt and perhaps the mailer would time out and reject the mail
back to the sender.

I recall that there were some methods for a person to simulate an
automatic net-mail-type host-to-host connection; that led me to wonder
if such a method could be used to trigger a remote machine to start up
such a process.

Regards, Will Martin

[John Gilmore]

When I was managing mail in the Sun internal network, I ended up adding
an option to sendmail which would process all queued mail which contained
a user-specified string: sendmail -Rstring. This could be used when
a host came up after being down, to clear out the queue. I also added
-Mqueueid to try to deliver a single message from the queue.

This change should be in the 4.3BSD sendmail. It can't be done from
the remote site, though, unless you can login from there. It would
probably not be hard to add a command to the SMTP server that would
do this. The security problem could be resolved by having the
server reply with "Yes, OK", break the connection, then go off and
run its queue, calling OUT to deliver the mail as usual.
--
John Gilmore {sun,ptsfa,lll-crg,ihnp4}!hoptoad!gnu jgil...@lll-crg.arpa
May the Source be with you!