Re: [libmicrohttpd] How to give busy message to second file upload client when 1st client file

[Christian Grothoff]

On Saturday 23 August 2008 10:30:15 am Sebastian Gerhardt wrote:
> Hello,
>
> Christian, I am a bit confused over this. Are you proposing that
> such a response should be built in the RequestCompletedCallback
> function? This seems counter-intuitive because the
> RequestTerminationCode is MHD_REQUEST_TERMINATED_COMPLETED_OK
> (Manual: "We finished sending the response."), suggesting that the
> response has already been sent.

No, you queue the response in the normal AccessHandlerCallback, at the place 
marked below (minor variant on the minimal_example.c from the distribution):

  if (0 != strcmp (method, "POST"))
    return MHD_NO;              /* unexpected method */
  if (&aptr != *ptr)
    {
     // If you want to generate an ERROR on POST,
    // this is where you WILL queue the response (in contrast
    // to what the above comment in minimal_example.c may
    // suggest...
     ret = MHD_queue_response(...);
      *ptr = &aptr; 
      return ret;
    }

(again, this is the NULL / called-before check that is usually done first in 
the AccessHandlerCallback).

> Reading the homepage, which says
>
>   "-- if the client queues a response during this first call, a 100
>    CONTINUE response will be suppressed, the request body will not be
>    read and the connection will be closed after sending the response."
>
> I would expect the MHD_AccessHandlerCallback to be the most appropriate
> place to built and queue this response--returning with MHD_YES.

Yes.

> This version works for GET requests, but it does not work for POST
> requests. The connection is just closed by MHD and nothing is sent.

For POST request it is important to do this in the right place; for GET 
requests the 100 CONTINUE does not really apply (since the client does not 
send anything after the header anyway).

> The only way to get a response sent for POST requests that I found so
> far is to create the postprocessor and do at least one post_data
> iteration.

Creating the postprocessor does nothing for the actual HTTP processing -- the 
entire postprocessor code does not interact with the networking code.

I hope this really clarifies the issue...

Christian