Re: [lwip-users] Browser finishes every HTTP GET request with a ACK RST, why ?

[groups]

Interesting interesting.

A while back I had put together my own web server on top of Espressif’s AT 
command set for ESP8266. The whole thing was working as a UI for a sealed 
embedded system with no display or keyboard.

The web pages that I would feed were crafted to re-request periodically, like 
every 10-15 seconds. (I can’t remember the details)

The page would refresh nicely for about a minute or 90 seconds to many 
minutes(again details), but eventually the page would write and then 
immediately blink to a server reset the connection screen.

After much frobbing and tweaking, I fired up Wireshark and I could see that all 
normal transactions would finish with an ACK, but the same request a little 
while later would finish with an [RST, ACK] being sent from the ESP8266 module.

Eventually my customer complained that this wasn’t good enough and needed to be 
fixed. I spent a whole lot of time and effort sending messages back and forth 
with Espressif, grabbing their latest code, building it all from source, 
testing, and adjusting to their undocumented API, but I definitely ran into the 
saving face culture when trying to report an issue. Eventually I had a system 
that would be stable if I reduced the re-request delay to about 9 seconds, 
because at 10 seconds the connection would get closed and never reopen again 
without a reboot (anyway, their code has issues and I traded one set of bugs 
with no path forward for another with some pretty terrible hacks as a work 
around).

So, Espressif’s stack is based on FreeRTOS, LwIP, and a whole bunch of magic. 
I’ve seen this same issue in their stack. I can’t say that it’s an LwIP 
problem, but it wouldn’t surprise me as well.

Hope this helps,

Andrei

> On 2021-September-15, at 07:37, Info <info@winformatik.ch> wrote:
> 
> Hi
> 
> I'm using lwIP (2.1.3-RC1) with the httpd web server from the apps directory 
> in my embedded application. After loading a web content from the web server a 
> periodic communication starts from the web browser that opened the website. 
> This all works, but after a view minutes the periodic communication gets 
> broken (the web server/lwIP stack itself does not crash). After a reload of 
> the web site the periodic communication is established again for a view 
> minutes.
> 
> In the attached Wireshark capture file I can see many frames (from the web 
> browser) with the set ACK RST flags. For me it not clear why the web browser 
> sends this frames and if it is the reason for the broken periodic 
> communication ? Any help and maybe some explanation would be very welcome.
> 
> I also activated the debugging output and the internal lwIP asserts, but this 
> did not help me to track down the problem. The web server does not support 
> encryption.
> 
> The lwIP uses FreeRTOS with the sys_arch files found in the contrib package.
> 
> IPs used in the Wireshark capture : The web server uses 192.168.3.131 and the 
> client (web browser) 192.168.10.103 .
> 
> Thank you very much for any help
> Roland
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