#!/usr/bin/perl

use strict;
use warnings;

use Net::Telnet;
my $t = Net::Telnet->new(
                         Timeout => 10,
                         Port => 6666
                        );
$t->open('mydataserver') or die "Can't connect to mydataserver: $!";

open my $fh, '>', '/tmp/file' or die "Can't write to /tmp/file: $!";
$fh->autoflush(1);

while (my $o = $t->getline())
{
    print $fh $o;
    # or $fh->print($o);
}
close $fh;