Re: [lwip-users] POST message Length Limitation

[address@hidden]

Am 08.10.2019 um 16:17 schrieb Siva Munnaluri:
> Reposting as my internet got disconnected, not sure the previous Post is
> posted or not.

The first one made it, no need to double-send...

> Hi LWIP Team,
>
> We are using
> http://git.savannah.nongnu.org/cgit/lwip.git/tree/contrib/examples/httpd/post_example
> for posting JSON data from a web page. If the JSON characters are more than
> 3000, entire data is not available on web server side.
>
> In lwipopts.h we found a vairable TCP_MSS which we set to (3000- 40). If we
> increase it to 4000 we are getting lwip_sanity_check

In the first message you wrote 400, not 4000. That confused me, but now
I see what you're getting at.

However, as Ajay wrote, your confusing things here. You should *never*
need to set TCP_MSS higher than 1460.

Instead, I guess you might have missed the fact that the post rx
callback gets called multiple times (as the segments arrive)?

Regards,
Simon

> #if TCP_SNDLOWAT >= (0xFFFF - (4 * TCP_MSS))
> #error "lwip_sanity_check: WARNING: TCP_SNDLOWAT must at least be 4*MSS
> below u16_t overflow!"
> #endif
>
> Is there a way to accept POST messages with more than 3000 characters. Our
> requirement is to post 15000 characters of JSON data.
>
> Regards,
> Siva