PHP use RS232 serial communication to send file

<?php
// --------------------------------------------------------------------------
// File name   : RS232_Server.php
//
//Procedure Description: 
//RS232_Client the procedures and the demonstration of a complete system in PHP to display 
//the RS232 serial communications applications. 
//Process to achieve a foundation of integrity, however the RS232 communication protocol 
//(HQB232), communication protocol format is as follows: 
//Agreement: 
//C-> S 01 //request for communication 
//S-> C 02 //response communications 
//C-> S LEN DATA //LEN said data (DATA) that the actual data length of DATA 
//C-> S 03 //end communication 
//Note: S, said that under the PC C-bit machine 
//HQB232 said HonestQiao the basis of presentation (Base) RS232 communication protocol, 
//including the agreement 
//Request and response, data frame structure. 
//Demonstration of the process for request and response communications, document
//delivery (data frame), the end of communication 
//Data frame structure of the current data for the current length of the HEX data 
//string (2 complement)
// --------------------------------------------------------------------------
set_time_limit(0);
exec('mode COM1: baud=9600 data=8 stop=1 parity=n xon=on');

$fd = dio_open('COM1:', O_RDWR);
if(!$fd)
{
        die("Error when open COM1");
}

$ff = dio_stat($fd);print_r($ff);
echo "HQB232 SERVER is listenning on COM1\n";
/// read
$len = 2;
$t=0;while (($t++)<1000)
{
        $data = dio_read($fd, $len);
        if ($data) {
                if($data==chr(0).chr(1)){
                        echo "S_RECV:01\n";
                        echo "S_SEND:02\n";
                        dio_write($fd,chr(0).chr(2));
                        break;
                }
        }
}

$handle = fopen("E:\\RS232\\TEST\\S_WAPMMonitor.exe", 'w');
/// read
$len = 2;
$t=0;while ($handle && ($t++)<1000)
{
        $len = 2;
        $data = dio_read($fd, $len);
        if($data==chr(0).chr(3)){
                echo "S_RECV:03\n";
                break;
        }
        elseif ($data) {
                $len = hexdec($data);
                if($len>0)
                {
                $data = dio_read($fd, $len);
                if($data){
                        fwrite($handle, str2hex($data));
                        echo "S_RECV:($len) ".microtime()."\n";
                }
                }
        }
}
fclose($handle);
dio_close($fd);

function str2hex($string)
{
        $str = '';
        for($i=0; $i<strlen($string); $i+=2){
                $str .= chr(hexdec(substr($string,$i,2)));
        }
        return $str;
}
?>

<?php
// --------------------------------------------------------------------------
// File name   : RS232_Client.php
// Procedure Description: 
// RS232_Server the procedures and the demonstration of a complete system in PHP 
// to display the RS232 serial communications applications. 
// Process to achieve a foundation of integrity, however the RS232 communication 
// protocol (HQB232), communication protocol format is as follows: 
// Agreement: 
// C-> S 01 // request for communication 
// S-> C 02 // response communications 
// C-> S LEN DATA // LEN said data (DATA) that the actual data length of DATA 
// C-> S 03 // end communication
// --------------------------------------------------------------------------
set_time_limit(0);
exec('mode COM2: baud=9600 data=8 stop=1 parity=n xon=on');

$fd = dio_open('COM2:', O_RDWR);
if(!$fd)
{
        die("Error when open COM2");
}

$ff = dio_stat($fd);print_r($ff);
echo "HQB232 CLIENT is start on COM2\n";
dio_write($fd,chr(0).chr(1));echo "C_SEND:01\n";
$len = 2;
$t=0;while(($t++)<1000)
{
        $data = dio_read($fd, $len);
        if($data==chr(0).chr(2)){
                echo "C_RECV:02\n";
                break;
        }
}
/*
$len = 2;
$t=0;while(($t++)<10)
{
        $sdata = sprintf("%03d",$t) . "=" . microtime() . " (" . randomkeys(rand(0,35)) . ")";
        $slen = strlen($sdata);
        $stxlen = sprintf("%02d",$slen);
        dio_write($fd,"$stxlen");
        dio_write($fd,"$sdata");echo "C_SEND:($stxlen)$sdata\n";
        //sleep(1);
}
*/

$handle = fopen ("E:\\RS232\\TEST\\WAPMMonitor.exe", "rb");
$data = "";
while ($handle && !feof($handle)) {
  $sdata = fread($handle, 127);
  $sdata = hex2str($sdata);
  $slen = strlen($sdata);
  $stxlen = sprintf("%02X",$slen);
  dio_write($fd,"$stxlen");
  dio_write($fd,"$sdata");echo "C_SEND:($slen) ".microtime()."\n";
  usleep(300);
}
fclose($handle);

dio_write($fd,chr(0).chr(3));echo "C_SEND:03\n";
dio_close($fd);

function randomkeys($length)
  {
   $pattern = "1234567890abcdefghijklmnopqrstuvwxyz";
   for($i=0;$i<$length;$i++)
   {
     $key .= $pattern{rand(0,35)};
   }
   return $key;
}

function hex2str($hexstring)
{
        $str = '';
        for($i=0; $i<strlen($hexstring); $i++){
                $str .= sprintf("%02X",ord(substr($hexstring,$i,1)));
        }
        return $str;
}
?>