socket_recvfrom在PHP中不返回任何数据

Question

为了与生物识别设备（ZKTeco K20）进行交互，我正在使用a library from github。现在，问题是我陷入了下面给出的connect（）函数中：

 public function connect($ip = null, $port = 4370)
        {
            if($ip != null)
            {
                $this->ip = $ip;
            }
            if($port != null)
            {
                $this->port = $port;
            }
            if($this->ip == null || $this->port == null)
            {
                return false;
            }
            $command = CMD_CONNECT;
            $command_string = '';
            $chksum = 0;
            $session_id = 0;
            $reply_id = -1 + USHRT_MAX;
            $buf = $this->createHeader($command, $chksum, $session_id, $reply_id, $command_string);
            socket_sendto($this->socket, $buf, strlen($buf), 0, $this->ip, $this->port);
            try
            {
                //Attention !!! here is the socket recve function that providing nothring in $this->received_data

                socket_recvfrom($this->socket, $this->received_data, 1024, 0, $this->ip, $this->port);

                if(strlen($this->received_data)>0)//here getting zero legth data
                {
                    $u = unpack('H2h1/H2h2/H2h3/H2h4/H2h5/H2h6', substr($this->received_data, 0, 8));
                    $this->session_id = hexdec($u['h6'].$u['h5']);
                    return $this->checkValid($this->received_data);
                } 
                else
                {
                    return FALSE;
                }
            }
            catch(ErrorException $e)
            {
                return FALSE;
            }
            catch(exception $e)
            {
                return FALSE;
            }
        }

socket_recvfrom 功能完全不提供任何数据。 $ this-> received_data的长度为零。我检查了我的IP地址和端口是否正确，这在另一个应用程序（设备供应商提供的内置应用程序）中连接正常。实际上，它没有提供任何错误，所以我无法找到问题。我怎么知道？

我也有try another library用于生物识别机器的交互。它也有同样的问题，我没有从 socket_recvfrom 接收数据。