Odd quirk with xargs and telnet Post: 302458127

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Top Forums UNIX for Dummies Questions & Answers Odd quirk with xargs and telnet Post 302458127 by treesloth on Wednesday 29th of September 2010 07:49:01 PM

09-29-2010

Registered User

Odd quirk with xargs and telnet

For a variety of strange reasons, I've set up an arrangement by which a server responds with "Hi there" if I connect on a specified port. This is a typical transaction:

Code:

# telnet example.com 3334
Trying 123.456.789.101...
Connected to example.com.
Escape character is '^]'.
Hi there
Connection closed by foreign host.

Now, I'm trying to use a quick and dirty way to do this concurrently, using xarg's -P (or max-procs, in some cases) option. Once this works, I'll increase the seq value, add -P concurrency, and be happy. The problem, though, is that I can't get the server's response to show up. Here's a trivial case:

Code:

# seq 1 | xargs -I DISCARD telnet example.com 3334
Trying 123.456.789.101...
Connected to example.com.
Escape character is '^]'.
Connection closed by foreign host.

So, the "1" should be discarded, as there is no DISCARD string in the command called by xargs, and the telnet command should be run. But, this trivial case should be the same thing as just running the telnet command alone since it's wrapped up in a negligible xargs. But, for some reason, the server's "Hi there" doesn't appear. Any idea why that is? I've tried redirecting stderr to stdout on the chance that it's some oddity in the way xargs handles errors, but no luck. I've also placed the telnet command into a little one-liner script and called that instead, without changing the output. Any suggestions? I've scratched my head many times. It didn't help... Many thanks in advance.

Last edited by treesloth; 09-29-2010 at 09:18 PM..

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LEARN ABOUT DEBIAN

courierpassd

COURIERPASSD(8) 						  Authentication						   COURIERPASSD(8)

NAME

       courierpassd - change passwords from across the network using the Courier authentication library

SYNOPSIS

       courierpassd [-hV] [-s SERVICE] [--stderr]

       courierpassd -s, --service SERVICE

       courierpassd --stderr

       courierpassd -h, --help

       courierpassd -V, --version

DESCRIPTION

       courierpassd  allows users to change their passwords from remote locations using the Courier authentication library. Usernames can be up to
       64 characters long while passwords can be up to 128 characters long.

       courierpassd uses the poppassd protocol for obtaining authentication tokens from the network. courierpassd is intended to  be  run  from  a
       super-server such as tcpserver or xinetd.

       The  service  specified	by the -s switch will depend on the particular authentication modules installed. Often 'login' will be appropriate
       but other possibilities include 'imap' and 'pop3'. This value defaults to 'login'. See the Courier documentation for a further  explanation
       of this switch.

       The  minimum  uid  that	courierpassd  will  attempt to change a password for can be set at compile time using the configure option --with-
       minuid.	courierpassd will refuse to change the password of a user whose uid is below this value. The default  value  is  100.  This  value
       should never be set to 0 as this would allow root's password to be changed from a remote location.

       A  second  configure  option,  --with-badpassdelay,  can be used to set the delay in seconds that courierpassd sleeps after an unsuccessful
       password change attempt. This feature is designed to make brute force attacks against passwords harder to perform. The default value is 3.

LOGGING

       Logging is done to syslog by default or to stderr if the --stderr switch is used.  courierpassd logs all password change  attempts  whether
       they are successful or not.

       courierpassd  does  certain  checks  on command line arguments so it is important to put --stderr first in the argument list if it is to be
       used in order for these checks to be logged properly.

EXAMPLE CLIENT-SERVER CONVERSATION
       All messages passed between server and client are text based allowing a client session to be easily mimicked  with  telnet.  Using  telnet,
       changing a user's password would look like this:

	    Connected to localhost.localdomain (127.0.0.1).
	    Escape character is '^]'.
	    200 courierpassd 1.1.2 hello, who are you?

	    user <username>

	    200 Your password please.

	    pass <current password>
	    200 Your new password please.

	    newpass <new password>

	    200 Password changed, thank-you.

	    quit

	    200 Bye.

	    Connection closed by foreign host.

BUGS

       If you've found a bug in courierpassd, please report it to freeware@arda.homeunix.net

SEE ALSO

       http://www.courier-mta.org/authlib/

       http://echelon.pl/pubs/poppassd.html

AUTHOR

       courierpassd was written by Andrew St. Jean

       Courier authentication library was written by Sam Varshavchik

       poppassd was written by Pawel Krawczyk based on an ealier version written by John Norstad, Roy Smith and Daniel L. Leavitt

GNU
/Linux							    20 Jan 2005 						   COURIERPASSD(8)