Re: [Expectperl-discuss] strange behavior with Net::Telnet, Expect, and Cisco 1924 Switches

[Bryan B. <br...@bu...>]

> Hello,
>
> I am experiencing some strange behavior when combining Expect with
> Net::Telnet when telnet'ing to Cisco 1924 switches.
>
> Scenario:
>
>                                         Cisco Gear
>
>                                    1924's     newer than 1924's
>                                 +----------+---------------------+
> Net::Telnet                     |  works   |       works         |
> Expect spawning system telnet   |  works   |       works         |
> Expect using Net::Telnet        | no work  |       works         |
>                                 +----------+---------------------+
>
> The reason I am concerned with using Net::Telnet with Expect is I have
> designed my program to be multithreaded and from what I read Net::Telnet
> is thread safe whereas IO-Tty is not.
>

I have used threading with expect on top of Net::Telnet successfully. 
Spawning a system telnet will, obviously, not work.

> The symptoms of what happens when using Expect and Net::Telnet to telnet
> to a 1924 is this:
>
> telnet negotiation (non printable characters) happens and then it looks
> like no other traffic is sent from the remote side. I am currently
> combing through tcpdump and wireshark analysis of this, but I thought I
> would send an email to the list to see if anyone had any ideas in the
> meantime.
>
> Here is some code that demonstrates what is happening:
> #!/usr/bin/perl
>
> use strict;
> use Expect;
> use Net::Telnet ();
>
> print "\n\n-----------START OF Net::Telnet-----------\n";
>
> my $t = new Net::Telnet("ghAS1.d.umn.edu");
> my @lines = $t->waitfor('/Selection.*/');
> print "@lines\n";
>
> print "\n\n-----------END OF Net::Telnet-----------\n";
> print "\n\n-----------START OF Expect with Net::Telnet-----------\n";
>
> my $e = new Net::Telnet("ghAS1.d.umn.edu");
> my $exp = Expect->exp_init($e);
> $exp->log_stdout(1);
> &expect_selection($exp);
>

Try this bit of code:

-- snip -->
my $e = new Net::Telnet(Prompt => '/Selection.*/');
$e->open("ghAS1.d.umn.edu");

my $exp = Expect->exp_init($e);
$exp->log_stdout(1);
&expect_selection($exp);
<-- end --


The open() method should finish the handshaking for you.  Also, if you
have to log in, it might help to do that within the Net::Telnet object
prior to expecting on top:

$e->login($user, $password);


Hope that helps.


Bryan
http://sourceforge.net/projects/rover