Re: [lwip-users] TCP Server RST after ACK

[Mr. Andrei Chichak]

Oh, interesting. A while back I had the same sort of issue with an ESP8266 
running ESP’s AT command interpreter wrapped around LwIP.
I’d repeatably get a SYN/RST event if I didn’t keep the channel busy enough. 
Unfortunately, with a http server, the person sitting at the keyboard 
determines how often packets will flow.
Unless I refreshed the screen automatically, something would timeout, and the 
next message would get a RST rather than an ACK.
I ended up working around it rather than persisting, it didn’t seem like ESP 
was willing to do any investigation lest they loose face(?).
(I guess I’m not adding anything other than “me too”)
A

> On 2022-November-29, at 08:50, Olaf Du <duolaf71@gmail.com> wrote:
> 
> Hello
> 
> I'm trying to port LwIP with FreeRTOS to the WCH32V307. It seems to kind of 
> work. DHCP is working, even though it sometimes takes quite some time to 
> gather an IP Address.
> 
> But TCP is not really working. I'm using httpd server in LwIP. Tracing it 
> down lead to getting a RST from the LwIP Server. The RST is sent due to an 
> incorrect ACK number.
> 
> Putting a printf into tcp_in.c after /* expected ACK number? */ lead to the 
> following:
> 
> Ackno is: 6511, expected ackno is: 6510 
> 
> This results in LwIP sending a RST.
> 
> Any idea why this can happen?
> 
> Thanks
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