[lwip-users] httpd: how to implement AJAX

[Giuseppe Modugno]

I'm trying to create a website with AJAX technology: the client polls, 
at regular intervals, the server with GET requests of file /status.json. 
The response is dynamic.

I could use only LWIP_HTTPD_CUSTOM_FILES and create the file at runtime 
in fs_open_custom(). It works, but I can't decode the query string, 
because it isn't passed to fs_open_custom() callback.

So I thought to use LWIP_HTTPD_CGI_SSI instead of 
LWIP_HTTPD_CUSTOM_FILES, but I have some difficulties to understand how 
it works.
First of all, the file /status.json must be present in the filesystem 
(fs_open() must return ERR_OK), otherwise httpd_cgi_handler() isn't 
called at all.
However I can't return any data in httpd_cgi_handler().

Any help?