why can't upload file into ftp target directory with curl?

[luofeiyu]

The file `d:/upload.sql` in my local pc can be uploaded into `my_ftp_ip/public_html/upload_ftp_put. sql` with code1.

<?php
    set_time_limit(0);
    $host = 'xxxx';
    $usr = 'yyyy';
    $pwd = 'zzzz';
    $src = 'd:/upload.sql';
    $ftp_path = '/public_html/';
    $des = 'upload_ftp_put.sql';
    $conn_id = ftp_connect($host, 21) or die ("Cannot connect to host");
    ftp_login($conn_id, $usr, $pwd) or die("Cannot login");
    $upload = ftp_put($conn_id, $ftp_path.$des, $src, FTP_ASCII); 
    print($upload);
?>

Now i rewite it with curl into code2.

code2:

<?php
  set_time_limit(0);
  $ch = curl_init();
  $host = 'xxxx';
  $usr = 'yyyy';
  $pwd = 'zzzz';
  $src = 'd:/upload.sql';
  $ftp_path = '/public_html';
  $dest = 'upload_curl.sql';
  $fp = fopen($src, 'r');
  curl_setopt($ch, CURLOPT_URL, 'ftp://user:pwd@host/'.$ftp_path .'/'. $dest);
  curl_setopt($ch, CURLOPT_UPLOAD, 1);
  curl_setopt($ch, CURLOPT_INFILE, $fp);
  curl_setopt($ch, CURLOPT_INFILESIZE, filesize($src));
  curl_exec ($ch);
  $error_no = curl_errno($ch);
  print($error_no);
  curl_close ($ch);
?>

The erroor info output is 6 .Why can't upload my local file into the ftp with curl?How to fix it?