請問一下如何透過 curl 上載image給對方？

curl_setopt($ch, CURLOPT_POST, 1);
  curl_setopt($ch, CURLOPT_CUSTOMREQUEST, "POST");
  curl_setopt($ch, CURLOPT_POSTFIELDS, $data_string);
  curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
  curl_setopt($ch, CURLOPT_HTTPHEADER, array(
      'Content-Type: multipart/form-data; boundary=boundary;', 
      'Content-Length: ' . strlen($data_string))
  );

因為對方不是 php 接收而是nodejs
如何實現跨server的文件上載？
有大神嗎