my $wheel = POE::Wheel::ReadWrite->new( ... );
  $heap->{readwrite}->{$wheel->ID} = $wheel;

##</code><code>##

sub agent_error {
  my ($heap, $function, $error, $wheel_id) = @_[HEAP, ARG0, ARG2, ARG3];
  print "SERVER: call to $function() failed: $error.\n";
  print "Disconnecting agent!\n";
  # Close the socket here...
  delete $heap->{readwrite}->{$wheel_id};
}