Re: [libmicrohttpd] Socket shutdown() and close() syscalls

[Christian Grothoff]

On 09/21/2012 04:46 PM, Enrico Migliore - FATTI srl wrote:
> Hi,
>
> I'm playing with MHD and I got 2 questions.
>
> Question 1
> ----------
> I noticed that MHD calls shutdown() and then close() after creating 
> each HTTP response. Is that correct?
Yes.
> If yes, I got another question:
> Since HTTP 1.1 allow the browser to issue many requests on the very 
> same socket, I expect MHD to keep the socket alive.
>
> What am I missing?
The browser needs to not send "Connection: close".  Also, as an 
application-developer, the MHD API hides keep alive from you, so you 
don't have to worry about it. Nevertheless, if the type of request 
allows it, MHD will do keep alive.
> Question 2
> ----------
> I can't find in the code and in the documentation the word "Keepalive".
>
> How MHD honors the Keepalive header which is usually present in ht 
> HTTP request issued by the browser?
*In HTTP 1.1*, all connections are considered persistent unless declared 
otherwise.  So MHD sets "Connection: close" IFF the type of request and 
reply make it impossible to use keep-alive and otherwise simply assumes 
that keep-alive will be used. You are free to manually (explicitly) set 
this connection header for your response if you want / believe the 
browser needs it.  You can also set "Connection: close" to force MHD not 
to use keep-alive.

You can find the respective code by looking for "Connection: close" or 
just the string "close" (in double quotes) in the MHD source code.


Happy hacking!

Christian