title: problems with Cross Origin Resource Sharing: both OSX Safari and iOS Safari fail after preflight request
body: <p>Recently I come into a trouble with CORS(Cross Origin Resource Sharing) request on Safari, both OSX and iOS, while the same request works perfectly on Chrome and Firefox. I follow <a href="https://www.w3.org/TR/cors/" rel="noreferrer">the documentation of W3C</a> and handle preflight request on server side, my response is like:</p>
  
  <pre><code>HTTP/1.0 200 OK
  Access-Control-Allow-Origin: http://192.168.1.96:4399
  Access-Control-Allow-Methods: POST
  Access-Control-Allow-Methods: GET
  Access-Control-Allow-Methods: OPTIONS
  Access-Control-Allow-Headers: Origin
  Access-Control-Allow-Headers: Authorization
  Access-Control-Allow-Headers: X-Requested-With
  Access-Control-Allow-Headers: Accept
  Access-Control-Allow-Headers: Access-Control-Request-Method
  Access-Control-Allow-Headers: Access-Control-Request-Headers
  Access-Control-Allow-Headers: DNT
  Access-Control-Allow-Headers: X-CustomHeader
  Access-Control-Allow-Headers: Content-Type
  Access-Control-Max-Age: 0
  Date: Fri, 25 Nov 2016 08:45:25 GMT
  Origin: http://192.168.1.96:4399
  Access-Control-Expose-Headers: Origin
  Content-Encoding: gzip
  Transfer-Encoding: chunked
  </code></pre>
  
  <p>Such response works fine on Chrome, Firefox, and Android Browser: a POST request is sent right after the preflight request. But on Safari, after server response the reflight request, I got such error message from console:</p>
  
  <pre><code>Failed to load resource: The network connection was lost.
  </code></pre>
  
  <p>I inspect the preflight response from server, but find it the same as above... After searching and trying so many times, I still can't make it work :-( <br/>
     Is there anybody that come across the problem before? Could anyone figure out what mistake I've made?<br/>
     Thanks very much in advance!</p>