ftp_base::Passive

	function Passive($pasv=NULL) {
		if(is_null($pasv)) $this->_passive=!$this->_passive;
		else $this->_passive=$pasv;
		if(!$this->_port_available and !$this->_passive) {
			$this->SendMSG("Only passive connections available!");
			$this->_passive=TRUE;
			return FALSE;
		}
		$this->SendMSG("Passive mode ".($this->_passive?"on":"off"));
		return TRUE;
	}