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Full Discussion: expect telnet unexpected delays
Special Forums UNIX and Linux Applications Infrastructure Monitoring expect telnet unexpected delays Post 302315601 by kp2a on Tuesday 12th of May 2009 10:35:43 PM
Old 05-12-2009
expect telnet unexpected delays
I must automatically monitor and manage a large number of boxes on our network.

I have been using perl/Net::Telnet and expect/telnet and also perl/ssh and expect/ssh to reach the command line of the remote boxes. Scripts are working but slow.

(Yes, I do use SNMP also but many boxes do not speak SNMP)

I believe that there is some protocol or terminal negotiating that I may be ignoring that blocks when the remote box sends a query and I do not respond.

I tried to read the RFC on Telnet which appeared to have an infinite number of options. My application is very simple: get to the remote command line.

Here is an example of expect/ssh (telnet exactly the same result) that includes unexpected data then the remote blocks for 10 seconds (local or remote default timeout?) then continues with expected response.
Code:
expect: set expect_out(buffer) "admin@10.100.72.223's password:"
send: sending "xxxxx\r" to { exp4 }
(logo deleted)
  MikroTik RouterOS 3.20 (c) 1999-2009       http://www.mikrotik.com/

  ^[[?62;9;c^[[39;3Rexpect: timed out

expect: does " \r\n\r\r\n\r\r\n\r\r\n\r\r\n\r\r\n\r\r\n\r\r\n\r\n\r  MMM      MMM     
(expected data deleted)
   MikroTik RouterOS 3.20 (c) 1999-2009       http://www.mikrotik.com/\r\n\r\r\n\r
\u001b[9999B\r\u001b[9999B\u001bZ  \u001b[6n" (spawn_id exp4) match glob 
pattern " > "? no

You see I was looking for the prompt, " > ", which does appear 10 seconds later!

Part does appear to be a terminal command. I have to guess the remote box is asking me a question and I am failing to answer.

Surprising is that using ssh rather than Telnet gives the same results.
Manual use of ssh or Telnet = no delays.
Script use of ssh or Telnet = 10 second delays for each send/expect cycle!

Can some one give me a clue???
 

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LEARN ABOUT DEBIAN

xrlogin

XRLOGIN(1)						      General Commands Manual							XRLOGIN(1)

NAME

       xrlogin - start an xterm that uses ssh (or optionally rlogin or telnet) to connect to a remote host

SYNOPSIS

       xrlogin [-l username] [-rlogin|-telnet] [xterm options] remote-host

DESCRIPTION

       Xrlogin opens an xterm window and runs ssh, rlogin or telnet to login to a remote host.

       Xrlogin	automatically  passes  the -name argument to xterm with a value of "xterm-hostname" where hostname is the name of the remote host.
       This allows the user to specify resources in their server's resource manager which are specific to xterms from a given host.  For  example,
       this  feature  can  be used to make all xterm windows to a given remote host be the same color or use a specific font or start up in a spe-
       cific place on the screen.  Xrsh(1) passes the same string so they are compatible in this regard.

       Xrlogin specifies that the default title for the new xterm will be "hostname" where hostname is the name of the remote host.  This and  the
       -name argument above can be overridden with xterm-options on the command line.

       One  could  also  use  xrlogin's sister command xrsh(1) to open a window to a remote host.  In the case of xrsh, the xterm would run on the
       remote host and use X as the connection protocol while xrlogin would run the xterm on the local host and use rlogin or telnet as  the  con-
       nection protocol.  See xrsh(1) for a discussion of the merits of each scheme.

OPTIONS

       -l username
	      When not using -telnet, use username as the id to login to the remote host.

       -rlogin
	      Use  the rlogin protocol to open the connection.	In general rlogin is preferred because it can be configured to not prompt the user
	      for a password.  Rlogin also automatically propagates window size change signals (SIGWINCH) to the remote host so that  applications
	      running there will learn of a new window size.

       -telnet
	      Use the -telnet protocol to open the connection. Use of telnet provided mostly for hosts that don't support rlogin.

COMMON PROBLEMS

       Make  sure  that  the  local  host  is  specified in the .rhosts file on the remote host or in the remote hosts /etc/hosts.equiv file.  See
       rlogin(1) for more information.

EXAMPLES

       xrlogin -bg red yoda
	      Start a local red xterm which connects to the remote host yoda using rlogin.

       xrlogin -telnet c70
	      Open a local xterm which connects to the remote host c70 using telnet.

SEE ALSO

       xrsh(1), rlogin(1), telnet(1)

AUTHOR

       James J. Dempsey <jjd@jjd.com> and Stephen Gildea <gildea@intouchsys.com>.

X Version 11							     Release 6								XRLOGIN(1)
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