Where's my STDOUT?

[Fatted Shmatted]

I'm writing a bidirectional client ( simplified version below),
messages to a server and replies from a server, however the client
doesn't need to wait for replies before sending further messages.
I can't get the child process to write to STDOUT (see code below).

STDOUT is:
[Connected to 127.0.0.1:2999]
TX'ed
done

If I change the while loop in the child loop to be:

while(1) instead of while(<$handle>)

I do get output on STDOUT but this stops me from receiving a SIG{CHLD}
(naturally child loop never exits).

STDOUT is:
[Connected to 127.0.0.1:2999]
TX'ed
RX'ed g
RX'ed o
RX'ed o
RX'ed d
RX'ed b
RX'ed y
RX'ed e
RX'ed

I've also tried a select on STDOUT in the child loop :

if(sysread($handle,$rxd,1,0))
{
my $old_fh = select(STDOUT);
$| = 1;
print "RX'ed ".$rxd."\n";
select($old_fh);
}

but no change...

Any idea's?

--

#!/usr/bin/perl
use strict;
use warnings;

$| = 1;

use IO::Socket;

my $host = "127.0.0.1";
my $port = "2999";
my $handle = IO::Socket::INET->new(Proto => "tcp", PeerAddr => $host,
PeerPort => $port) or die "can't connect to port $port on $host: $!";

$handle->autoflush(1);
print STDERR "[Connected to $host:$port]\n";

my $child_pid = "";
die "can't fork: $!" unless defined($child_pid = fork());

if ($child_pid)
{
$SIG{CHLD} = sub{ print "done\n"; exit(0) };
print $handle "hello";
print "TX'ed\n";
$handle->shutdown(1);
sleep;
}
else
{
my $rxd = "";
while(<$handle>)
{
if(sysread($handle,$rxd,1,0))
{
print "RX'ed ".$rxd."\n";
}
}
}

***
server for this test could be:

$ netcat -l -p 2999 < out.put > in.put

Where out.put contains the word goodbye

***

 

[xhoster]

while(<$handle>)

This reads a line into $_, which is then ignored.

{
if(sysread($handle,$rxd,1,0))

Since you already read the data with <>, there is probably nothing to
sysread at that point.

You could use something like:

while(sysread($handle,$rxd,1,0)) {
print "RX'ed ".$rxd."\n";
}

But that doesn't distinguish between eof and errors on the handle.

Xho

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