http://www.perlmonks.org?node_id=979541

vdubjunkie has asked for the wisdom of the Perl Monks concerning the following question:

It's hard to explain the elation I felt when I found a working ssh module recently. I've hit a low spot though, when I attempted to take my functioning routine and wrap it up inside a list of hosts. 
#!/usr/bin/perl

use strict;
use Net::SSH2;
my $hf = 'list.txt';
my $user = 'user';
my $pass = 'pass';
my $ssh = Net::SSH2->new();
$ssh->debug(1);
open (L,"<$hf") || die "$!";
while(<L>) {
  chomp $_;
  print "Connecting now..\n";
  $ssh->connect("$_") || warn "$!";
  $ssh->auth_password("$user","$pass");
  my $chan = $ssh->channel();
  $chan->exec('dir');
  $chan->close();
}
close L;

[download]
This was a test script I used to simplify troubleshooting, and I still got the following result: 
# ./test.pl
Connecting now..
libssh2_channel_open_ex(ss->session, pv_channel_type, len_channel_type
+, window_size, packet_size, ((void *)0) , 0 ) -> 0x841ed400
Net::SSH2::Channel::DESTROY
Connecting now..
Resource temporarily unavailable at ./test.pl line 14, <L> line 2.
libssh2_channel_open_ex(ss->session, pv_channel_type, len_channel_type
+, window_size, packet_size, ((void *)0) , 0 ) -> 0x0
Can't call method "exec" on an undefined value at ./test.pl line 21, <
+L> line 2.
Net::SSH2::DESTROY object 0x8663b6c0

[download]
It's the "Resource is temporarily unavailable" that I'm seeing when I don't have the debug running. I even threw in a sleep to see if that might help. The first host connects perfectly, and I can run commands, etc. That second host (which by the way IS online) fails reliably. Any suggestions?!

Replies are listed 'Best First'.
Re: Net::SSH2 woes
by syphilis (Archbishop) on Jul 02, 2012 at 23:37 UTC
    I think the problem is that you're using the same Net::SSH2 object ($ssh) to connect to different hosts, though it's not exactly clear to me that this *ought* to be a problem at all.
    Try the below rendition (untested). It creates a new Net::SSH2 object for each host. 
    use strict;
use Net::SSH2;
my $hf = 'list.txt';
my $user = 'user';
my $pass = 'pass';
open (L,"<$hf") || die "$!";
while(<L>) {
  chomp $_;
  my $ssh = Net::SSH2->new();
  $ssh->debug(1);
  print "Connecting now..\n";
  $ssh->connect("$_") || warn "$!";
  $ssh->auth_password("$user","$pass");
  my $chan = $ssh->channel();
  $chan->exec('dir');
  $chan->close();
  undef $ssh;
}
close L;

    [download]
    Perhaps the undef $ssh; is unecessary.

    Cheers,
    Rob
[reply]
[d/l]
[select]

      The SSH session is created in Net::SSH2->new(), not $ssh2->connect(). Each SSH session can be used for only one connection, therefore, to connect to a new host, a new SSH session is required. So, you are correct: Net::SSH2->new() must be called for each host, inside the loop.

[reply]
[d/l]
[select]
      You had it. I'm actually a bit embarrassed I didn't think of it myself, but I am a bit rusty. I can swear I pulled this format from an example I found some place. Don't people test their examples?! Thanks guys. perlmonks has always been the only place I need for PERL help!
[reply]
Re: Net::SSH2 woes
by salva (Canon) on Jul 03, 2012 at 05:31 UTC
    The first thing you should do is to ensure you have the latest version of Net::SSH2 compiled against the latest version of libssh2.

    Try also Net::OpenSSH.

[reply]

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