Telnet over SSH2 from Windows

[Hessu]

Hello,

I would like to connect from Windows XP to SSH2 server and from there establish a telnet connection to device. I would like to send a command to this device, wait expected prompt from the telnet session over SSH connection and read the result. So far best results have been with Net::SSH2. The problem is the telnet connection.

The problem is that after I issue 'telnet <IP Address>' command, I cannot read the data without breaking the command sending/reading. If I read the result once after telnet has been established, I get after that only the command that was sent. For example after sending the telnet command, I read the result to look for username prompt and send the username. After this I get only the username that was sent as a result, not the actual output. Seems like output and input are mixed after first read.

I can issue the commands over telnet session quite nicely if I do not read the results at all. But unfortunately, I need to parse the output and decide following actions based on collected data. This might be possible with several sequential sessions, but I am looking send command, wait expected data and read response type of solution on Windows machine. I am trying to compile this as executable with ActiveState tools and for this reason I don't think that Cygwin is an option.

Is there a way to do this on Windows machine? Is this somehow related to terminal settings that I should modify before establishing the telnet session? Newbie question, but I was not able to find the module where implementation of $channel->read() really is?

Thank You

#!/usr/bin/perl

# Tested with ActiveState perl version 5.8.8 on Windows XP SP3.

use strict;
use warnings;

use Net::SSH2;    # Using version 0.28.
use Data::Dumper;

#Net::SSH2->debug(1);

use constant NEWLINE => qq{\n};

my $g_ssh_server  = '<10.10.10.10>';        # SSH server addresss
my $g_username    = '<username>';
my $g_password    = '<password>';
my $g_prompt      = '<ssh server prompt>';
my $g_telnet_cmd  = 'telnet <10.10.10.10>'; # Command to telnet
my $g_ssh         = undef;
my $g_channel     = undef;

# Connection opened with shell.
SSH2Open(\$g_ssh, \$g_channel);

# Separate commands are executed and read nicely.
SSH2Send($g_ssh, $g_channel, "\n", $g_prompt);
SSH2Send($g_ssh, $g_channel, 'ls -al', $g_prompt);
SSH2Send($g_ssh, $g_channel, 'uname -a', $g_prompt);
SSH2Send($g_ssh, $g_channel, 'ls -l', $g_prompt);

# Starting telnet causes problems if command output is read
SSH2Send($g_ssh, $g_channel, $g_telnet_cmd, '<expect username prom>');
SSH2Send($g_ssh, $g_channel, 'username',    '<expect password prom>');
SSH2Send($g_ssh, $g_channel, 'passowrd',    '<expect terminal prom>');
SSH2Send($g_ssh, $g_channel, 'ls -al',      '<expect terminal prom>');

# Read to test commands without reading after each command.
SSH2Read($g_ssh, $g_channel);

sub SSH2Open{
  my $ssh2    = shift; # OUT
  my $channel = shift; # OUT

  ${$ssh2} = Net::SSH2->new();
  ${$ssh2}->connect($g_ssh_server) or die $!;
  ${$ssh2}->auth_password($g_username, $g_password) or die 'Auth. Fail
+ed';
  ${$channel} = ${$ssh2}->channel();
  ${$channel}->pty('vt80'); # To get the prompt also.
  ${$channel}->shell();

  return;
}

sub SSH2Send{
  my $ssh      = shift; # IN
  my $channel  = shift; # IN - Created channel
  my $command  = shift; # IN - Command to be sent
  my $waitfor  = shift; # IN - String to be waited for.

  my $found    = 0;
  my $string   = q{};
  my @result   = ();

  print "===============================\n";
  print "send command ($command)\n";
  $channel->write(($command . NEWLINE));

  if(0)
  {
    # Read response with method 1. This works randomly depending on
    # latency I quess. This may not read all of the data or last
    # command reads the data for every command.
    $string = q{};
    while( <$channel> ) {
      $string = $string . $_;
    }
  }

  if(0)
  {
    # Read response with method 2. same as method 1.
    $string = q{};
    my @result = readline($channel);
    $string = $string . join("\n", @result);
  }

  # Read response with method 3. Try polling until requested prompt
  # found. Based on http://search.cpan.org/~remi/Net-SSH2-Simple/.
  if(1)
  {
    my( $n, $buffer );
    my @poll = ({handle => $channel, events => ['in', 'ext', 'err']});
    $string = q{};
    $channel->blocking(0);
    while(not $channel->eof and not $found) {
      $ssh->poll( 2000, [ @poll ] ); # 2 seconds
      print "poll" . Dumper \@poll;
      foreach my $poll ( @poll ) {
        foreach my $event ( qw( in ext ) ) {
          next unless $poll->{revents}{$event};
          if($n = $channel->read( $buffer, 10_240, $event eq 'ext' )){
            $string = $string . $buffer;
            #print "read string ($n) - $string\n";
          }

          # Check if the requested data was read.
          $found = __test_waitfor($waitfor, $string);
        }
      }
    }
  }

  print "response: $string\n";
  print "===============================\n";

  return;
}

sub SSH2Read{
  my $ssh      = shift; # IN
  my $channel  = shift; # IN

  my $string   = q{};

  if(0)
  {
    $string = q{};
    while( <$channel> ) {
      $string = $string . $_;
    }
    print "string $string\n";
  }

  return;
}

sub __test_waitfor{
  my $waitfor  = shift; # IN
  my $string   = shift; # IN

  my $last_line = q{};
  my $found     = 0;

  # If user defined waitfor, it is checked from last line of the
  # string. Otherwise the string is just tested for couple of
  # characters.
  if( $waitfor ) {
    ($last_line) = $string =~ m/\n?(.*)\z/x;
    if( $last_line ) {
      print "last line ($last_line) wait ($waitfor)\n";
      if( $last_line =~ m/$waitfor/ ) {
        $found = 1;
      }
    }
  }
  elsif( 5 < length $string ) {
    $found = 1;
  }

  return $found;
}