Re^2: Networking without a network

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]

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Re^3: Networking without a network by zentara (Cardinal) on Feb 23, 2010 at 16:44 UTC
There are a few programs around, that don't behave well with pipes, when they were meant to be run from a terminal. Maybe you have one there? Some commonly tried approaches are usually attempted. First try a sysread instead of <> on $reader, and use IO::Select to detect data in the pipeline. `#pseudocode my $data while ($select->can_read){ if ( (my $length = sysread $reader, $data, 4096) > 0) { # do something with $data } }` [download] You might also want to test out a different IPC module, which may work better than IPC2. See I got IPC::Open3 to work! and Script hangs when called via IPC::Open3 and IPC3 buffer limit problem and Script hangs when called via IPC::Open3 for example. The IPC3 links above have code showing how to combine IO::Select with sysread....... that is your best first shot. The basic idea should work with IPC2 also. The last resort, if select and sysread fail, is to use a pty, like in Re: monitoring memory load. We really need to know what this program does. What does it expect on input, and what output does it deliver? Somehow, your data just sits in the pipeline buffer. You might also try the Expect module. I'm not really a human, but I play one on earth. Old Perl Programmer Haiku	[reply] [d/l]
Re^3: Networking without a network by JavaFan (Canon) on Feb 23, 2010 at 14:27 UTC
Your comment suggests that the program is waiting for `/usr/local/script/netdiag` to write something. Which may mean the "problem" (or rather, the fix) lies in said program - not in your small script. Considering this is a networking program - perhaps netdiag is expecting `$CR$LF` as line endings, not just `$CR` (why $CR there, not $LF?). It hasn't seen a full line yet, so it's not going to write anything.	[reply] [d/l] [select]
Re^3: Networking without a network by zentara (Cardinal) on Feb 23, 2010 at 16:53 UTC
But I must have stated my problem badly. No.... I must have read your problem based only on the first paragraph.... sorry. my bad. But my other answer is good. :-) use sysread + select I'm not really a human, but I play one on earth. Old Perl Programmer Haiku	[reply]