How to use DNS hosts resolver myself when using CFReadStreamOpen
<p>I use NSInputStream to send a http request . Now I need to make the request use my customized dns server . I have read part of the source code of CFNetwork without no answer. </p>

<pre><code>CFHTTPMessageRef myRequest = CFHTTPMessageCreateRequest(kCFAllocatorDefault,
        requestMethod, myUrl, kCFHTTPVersion1_1);
CFHTTPMessageSetBody(myRequest, bodyData);
CFHTTPMessageSetHeaderFieldValue(myRequest, headerField, value);

CFReadStreamRef myReadStream = CFReadStreamCreateForHTTPRequest(kCFAllocatorDefault, myRequest);

CFReadStreamOpen(myReadStream);
</code></pre>
