Ok I've rewriten your script as follows - 
#!/usr/bin/perl

use strict;
use warnings;
use IO::Socket;

my $pid = fork();  die "couldn't fork" unless defined($pid);
if ($pid) {  # SERVER
    my $server = IO::Socket::INET->new(
        Proto     => 'tcp',
        LocalPort => 9999,
        Listen    => 1,
        ReuseAddr => 1,
    );
    die "couldn't setup server" unless $server;
    
    my $client = $server->accept();
    $client->autoflush(1);
    while (<$client>) {
         
       print "DUMP:\n";
       use Data::Dumper;
       print Dumper($_); 
       print "DUMP END\n";       

        if    (/hello/) { print $client "nice to meet you\n" }
        elsif (/quit/)  { print $client "bye\n"; }
        else{ print $client "??\n"; }
    }
    close $client;

} else {     # CLIENT
    sleep 1; # wait for server to get ready
    
    my $sock1 = IO::Socket::INET->new( 
        Proto     => 'tcp',
        PeerAddr  => "localhost",  
        PeerPort  => 9999, 
    );
    die "couldn't connect" unless $sock1;
    
    open my $sock2, '+<&='.$sock1->fileno() or die $!;
    
    printf "sock1         = %s\n",   $sock1;
    printf "fileno(sock1) = %d\n",   $sock1->fileno();
    printf "autoflush     = %s\n\n", $sock1->autoflush() ? "ON":"OFF";
    
    printf "sock2         = %s\n",   $sock2;
    printf "fileno(sock2) = %d\n",   $sock2->fileno();
    printf "autoflush     = %s\n\n", $sock2->autoflush() ? "ON":"OFF";

    my $resp;

    print $sock1 "hello\n";
    $resp = <$sock1>;  print $resp;
    print $sock1 "quit\n";
    $resp = <$sock1>;  print $resp;
    exit;
}

[download]
And when I print out the values for sock1 I get -
sock1         = IO::Socket::INET=GLOB(0xd9327c)
fileno(sock1) = 4
autoflush     = ON

sock2         = GLOB(0xe424b4)
fileno(sock2) = 4
autoflush     = OFF

DUMP:
$VAR1 = 'hello
';
DUMP END
nice to meet you
DUMP:
$VAR1 = 'quit
';
DUMP END
bye

[download]
But if I print for socket2 (by changing the last five lines of the script) I get - 
sock1         = IO::Socket::INET=GLOB(0xd93504)
fileno(sock1) = 4
autoflush     = ON

sock2         = GLOB(0xe42714)
fileno(sock2) = 4
autoflush     = OFF

DUMP:
$VAR1 = 'hello
';
DUMP END
nice to meet you
DUMP:
$VAR1 = 'nice to meet you
';
DUMP END
??
DUMP:
$VAR1 = 'quit
';
DUMP END

[download]
Where is that extra message comming from. Am I not really flushing?
Thanks again!

In reply to Re^2: Problem extracting socket from fileno by Anonymous Monk
in thread Problem extracting socket from fileno 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.