#!/usr/bin/perl -l

use strict;
use warnings;
use Net::Telnet::Options;

my $nto = Net::Telnet::Options->new();

my($ssocket) = 'This is a test';

open my $socket, "<", \$ssocket 
  or die "Can't open socket scalar: $!";
my $data = chr(255);
my $returned = $nto->answerTelnetOpts($socket, $data);
print "SSocket : ", join(' ', map({ ord $_; } split(//, $ssocket)));
close $socket;
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I replied to your previous node before I noticed this one.

The problem is neither in Linux or Telnet.pm. It is working as specced. According to the Telnet RFCs, if you want to sent \xff as data you need to sent it twice to escape the escape. For example, to send the sequence: (\xff \xde), send (\xff \xff \xde).

Hi thundergnat,

Thanks for the responses. From the client's side I can send 2 FFs to escape the escape that's not a problem, the problem comes in when I readback data from the controller, I can't control the output from the WATLOW and it won't print 2 FFs! Basically I need to get the data as it is but since Telnet.pm or Fedora interprets the IAC as a command its not going to work :(

Hi Khen1950fx

I'm not entirely sure how the options work. For my script I'm currently using Net::Telnet() module. As I am quite new to Perl, how do I go about including the extra options module to my script? Thanks!

If you cannot change the sending side, I think that using Net::Telnet is the wrong tool. Have you considered using simple plain sockets, via connect? All more specific layers will likely have problems with the data potentially containing delimiters.

Also see Modbus. Especially Modbus::Client seems to be a potential solution, if you open the socket first and then pass it in to the Modbus::Client constructor.

Actually the problem is not with the Watlow but with the Digi CM-32. The Watlow is communicating to the Digi CM-32 in Modbus RTU which has no issues with \xff characters.

See if there is some option you can set in the Digi CM-32 to allow "raw" data mode or some such. If not, you may need to implement your ethernet communication with raw TCP sockets using IO::Socket::INET, which is what Net::Telnet uses under the hood.