Thank you zentara, a good link and a good example concerning socket programming. I'll save it for future reference.
But I must have stated my problem badly. What I really want to do is running our app from the command line. Not through inetd, i.e. not by connecting to port 7000 (in this case).

I can write a small perl script communicating to this application connecting to tcp port 7000 etc etc. But I am trying to do something different now.

I may have misunderstood almost everything, but my approach was to hook inte the app's STDIN/STDOUT assuming those are the handles to hook. Let me illustrate with some code. 

#!/usr/local/bin/perl
use strict;
use warnings;
use IPC::Open2;
use IO::Handle;

$/ = "\r";
my $CR = "\r";
my $NL = "\n";

my @msg = ('INIT', 'STATUS', 'QUIT' );

my ($reader, $writer) = (IO::Handle->new, IO::Handle->new);
my @program_and_arguments = ('/usr/local/script/netdiag');

eval {
        open2($reader, $writer, @program_and_arguments);
};
if ($@) { 
    if ($@ =~ /^open2/) {
        warn "open2 failed: $!\n$@\n";
        return;
    }
    die;
}

select $writer;
$|++;
select STDERR;
$|++;
select STDOUT;
$|++;


print STDERR "Here 1\n";
my $req = shift @msg;
print $writer $req, $CR;
print STDERR "Here 2\n";                   # We come here, than it han
+gs

my $answer = <$reader>;
die "1" unless $answer;

print STDERR "SVR:$answer$NL";
[... keep up the dialog...]

print STDOUT "Done$NL";
__END__

[download]
/L

In reply to Re^2: Networking without a network by Anonymous Monk
in thread Networking without a network by Anonymous Monk

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.