Hey BrowserUk , I modified my pure IO::Select server to use sysread, and your "eternal a" script dosn't hang it anymore. Here is the server, client, and your hanger-script.

I run the server, then start one conventional client, then your hanger-script, then a second client. All works well. Is this the mythical Holy Grail select script that you have been looking for? :-) It may not be perfected yet, but it works non-blocking here.

Server:

#!/usr/bin/perl
use warnings;
use strict;
use IO::Socket;
use IO::Select;

my @sockets;
my $machine_addr = 'localhost';
my $main_sock = new IO::Socket::INET(LocalAddr=>$machine_addr,
      LocalPort=>1200,
      Proto=>'tcp',
      Listen=>3,
            Reuse=>1,
            );

die "Could not connect: $!" unless $main_sock;
print "Starting Server\n";

my $readable_handles = new IO::Select();
$readable_handles->add($main_sock);

while (1)
{
  
######################################################################
   #this line caused 100% cpu usage ( thanks to BrowserUk for pointing
+ this out)
   #my ($new_readable) = IO::Select->select($readable_handles, undef, 
+undef, 0 );
   #should be
   my ($new_readable) = IO::Select->select($readable_handles, undef, u
+ndef, undef );
####################################################################
  foreach my $sock (@$new_readable)
  {
    if ($sock == $main_sock)
    {
      my $new_sock = $sock->accept();
      $readable_handles->add($new_sock);
    }
    else
    {
   
     my $count = sysread $sock, my $buf, 1024; 
   
      print "$count\n";
   
      if ($buf)
      { 
        print "$buf\n";
        my @sockets = $readable_handles->can_write(1);
    print "@sockets\n";
    #print $sock "You sent $buf\n";
    foreach my $sck(@sockets){print $sck "$buf\n";}
        
      }
      else
      {
        $readable_handles->remove($sock);
        close($sock);
      }
    }
  }

}
print "Terminating Server\n";
close $main_sock;
getc();
[download]

The client:

#!/usr/bin/perl -w
use strict;
use IO::Socket;

my ( $host, $port, $kidpid, $handle, $line );

( $host, $port ) = ('localhost',1200);

my $name = shift || '';
if($name eq ''){print "What's your name?\n"}
chomp ($name = <>);


# create a tcp connection to the specified host and port
$handle = IO::Socket::INET->new(
    Proto    => "tcp",
    PeerAddr => $host,
    PeerPort => $port
  )
  or die "can't connect to port $port on $host: $!";
$handle->autoflush(1);    # so output gets there right away
print STDERR "[Connected to $host:$port]\n";

# split the program into two processes, identical twins
die "can't fork: $!" unless defined( $kidpid = fork() );

# the if{} block runs only in the parent process
if ($kidpid) {

    # copy the socket to standard output
    while ( defined( $line = <$handle> ) ) {
                      print STDOUT $line;
                      }
    kill( "TERM", $kidpid );    # send SIGTERM to child
}

# the else{} block runs only in the child process
else {

    # copy standard input to the socket
    while ( defined( $line = <STDIN> ) ) {
        print $handle "$name->$line";
    }
}
[download]

And your hanger-test script

perl -MIO::Socket -E ' $s=IO::Socket::INET->new("localhost:1200"); $s-
+>send( "a" ); sleep 1e6 '
[download]