use strict;
use warnings;

use IO::Handle;
use IO::Select;
use IO::Socket;
use Sys::Hostname;

# Listen on port 1234
# Forward requests to host <2nd parameter> (default current host), port <1st parameter>
my $p = shift;
my $s = shift || hostname();
print "Forward to server: $s, port: $p\n";

# Set proxy parameters
my %proxy;
$proxy{server_host} = $s;
$proxy{server_port} = $p;
$proxy{proxy_port}  = 1234;
$proxy{proxy} = IO::Socket::INET->new (
   LocalPort => $proxy{proxy_port},
   Type      => SOCK_STREAM,
   Reuse     => 1,
   Listen    => 10);
binmode $proxy{proxy};

# Now ready to listen and forward the session
print "Ready!\n";
# Wait for a connection from SQL*Plus
doit();
print "Goodbye!\n";
exit;

sub doit {
  my $rc;

  my $client = $proxy{proxy}->accept() || die "Unable to reach client:\n$!";
  binmode $client;

  my $server = IO::Socket::INET->new (
           PeerAddr => $proxy{server_host},
           PeerPort => $proxy{server_port});
  if ( $server ) { binmode $server; }
  else { $rc = $!; }

  $client->blocking(0);
  $server->blocking(0) if $server;

  my $select = new IO::Select;
  $select->add($server);
  $select->add($client);

  autoflush $server if $server;
  autoflush $client;

  while ( my @ready = $select->can_read() ) {
    foreach my $fd (@ready) {
      my $buf="";
      if ( $fd == $client ) {
        sysread ($client, $buf, 1024) || return;
        if ( $server ) { print $server $buf; }
        else { print "Unable to reach server:\n$rc\n"; exit 0; }
      }
      if ( $fd == $server ) {
        sysread ($server, $buf, 1024) || return;
        print $client $buf;
      }
    }
  }
}

client      -> proxy       -> database
XP 32-bit   -> XP 32-bit   -> XP 32-bit      ok
XP 32-bit   -> XP 32-bit   -> Win7 64-bit    KO
XP 32-bit   -> Win7 64-bit -> XP 32-bit      ok
XP 32-bit   -> Win7 64-bit -> Win7 64-bit    ok
Win7 64-bit -> XP 32-bit   -> XP 32-bit      ok
Win7 64-bit -> XP 32-bit   -> Win7 64-bit    KO
Win7 64-bit -> Win7 64-bit -> XP 32-bit      ok
Win7 64-bit -> Win7 64-bit -> Win7 64-bit    ok