Newsgroups: comp.unix.shell, comp.sys.sun.misc, comp.sys.sun.admin, comp.protocols.tcp-ip
Followup-To: comp.sys.sun.admin
From: hoey@AIC.NRL.Navy.Mil (Dan Hoey)
Date: 4 Jun 92 22:11:43 GMT
Subject: Unix shell TCP tools and /usr/etc/mconnect bug

I occasionally write simple TCP clients as a shell script.  The only
tool I really need for the job is a filter that will connect the
standard input and output to the streams of a TCP connection.  Once
upon a time I used telnet as the filter, but that had a problem: When
the connection dropped, you would lose the end of the
output--sometimes all the way back to the beginning.

So I was happy to see mconnect(8) in the Sun distribution (did Sun
write it, or is from BSD?) because it does exactly the right thing for
me--almost.  It has three problems, and two of them are minor.  The
third, however, is a fairly severe bug, and I would like suggestions
for solving it.

Problem 1: Mconnect does not translate NETASCII back to ASCII, so you
get carriage returns (^M) in the output.  I pipe the output through
  tr -d '\015'
and that solves the problem.  It would be faster, though, if mconnect
did the translation.  Also, I'm a little concerned that mconnect may
not be inserting carriage returns on input, though I haven't run into
problems with that yet.

Problem 2: Mconnect prints
  connecting to host nic.ddn.mil (192.112.36.5), port 101
  connection open
at the beginning of the output.  But most tcp services put out some
sort of initial greeting that I have to ignore anyway, so ignoring two
more lines is no problem.  Still, this stuff should be on stderr.

Problem 3: Mconnect SOMETIMES inserts
  connecting to host nic.ddn.mil (192.112.36.5), port 101
  connection open
at some random place in the output.  It is apparently timing
dependent, and I have no source to find out where it's coming from,
and I really don't want to have to delete those lines when they could
be valid output.

For instance, the command

  echo ALL-MIL | /usr/etc/mconnect -p 101 nic.ddn.mil | grep -n connect

gives me output like

  1:connecting to host nic.ddn.mil (192.112.36.5), port 101
  2:connection open
  1436:connecting to host nic.ddn.mil (192.112.36.5), port 101
  1437:connection open

where the second set of line numbers occur somewhere between 1000 and
5000.  Has anyone fixed the problem 3 bug?

Is there a publicly available version of mconnect or equivalent?  So
far I've found "tcpcon" in Simtel20's PD6:<UNIX-C.NETWORKS> directory,
but that doesn't have the code to wait for the output to drain.

Please mail me your suggestions, and I'll report any solutions that
come in.

Dan Hoey
Hoey@AIC.NRL.Navy.Mil