HttpRequest.InputStream and HttpResponse.OutputStream, when are they closed?

 I want to read from HttpRequest.InputStream and write to HttpResponse.OutputStream multiple times. It seems I cannot write first, then read something.
I can only first read from  HttpRequest.InputStream, then write to HttpResponse.OutputStream, that works, like a browser/iis interaction. But I need to do more in a custom HTTP client.

After I write to HttpResponse.OutputStream, it seems the HttpRequest.InputStream is closed, I cannot read anything anymore.
Is there a way that I can read/write multiple rounds so the custom HTTP clients can talk to asp.net application like a ordinary client/server application?
 
 
...