php socket 관련 함수중에서 socket 상태를 체크하는 함수가 없어서...
get_socket_status() 의 파라메타는 stream 이기 때문에 socket 을 파라메터로 사용할 수
없음


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## chkeck socket is ESTABLISHED ?
## return value
##   -1 : $sock is empty or is not resource
##    0 : $sock event happend(is not ESTABLISHED)
##    1 : $sock is ESTABLISHED
##
function socket_connect_status(&$sock)
{
  if(!$sock || !@is_resource($sock)) return -1;

  ##   0 Success
  ##   1 Operation not permitted
  ##  56 Socket is already connected
  ## 106 Transport endpoint is already connected
  ##
  $ecode = @socket_last_error($sock);
  if($ecode!=106 && $ecode!=56) return 0; // is not connected

  $r = array($sock);
  $s = @socket_select($r,$w=NULL,$e=NULL,0);

  ## $s === 0 nothing interesting happened => ESTABLISHED
  ## $s  >  0 some something interesting happened
  ## $s === FALSE socket_select() error
  ##
  return ($s===0) ? 1 : 0;
}
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