[lwip-users] http server problems/bug

[lampo]

*Problem*
 
 web server                       <------ GET  HTTP/1.1-----   web Client
 web server (FIN_WAIT_1)  -------- FIN,PSH----------->   web Client
 web server (FIN_WAIT_2)  <-------- ACK-------------      web Client 
 (*sometimes ACK not received by web server !!  we find it does not enter
FIN_WAIT_2 state, but the low_level_input actually received the ‘ACK’* )
 web server                     <-------- FIN--------------      web Client
 web server                      -------- ACK------------->      web Client
 (......some time like half minutes later, *re-transmission* occurs)
 web server                        --------FIN,PSH------->       web client
 web server                       <------RST-------------         web client
 (*it seems the whole pcb(tcp_pcb) is reset* ! Because all other connections
fail ,including tcp client which is an independent thread )
Then after a long time(sometimes even minutes later), all connection
recovered.

*Testing Conditions*
Lwip 1.4.1 ,   web server is based on example of ‘httpserver_raw’, that
means the web server is inside the tcpip_thread  rather than an independent
thread.

web server(MCU,STM32) IP :  192.168.0.10
web client(PC,IE browser) IP:  192.168.0.14 

Some PC occurs much more frequently while others seldom occurs.


*Our doubts*
1. Why the upper level didn’t receive ‘ACK’ while low_level_input did?
2. In http server application, how to avoid reseting the whole tcp pcb(if my
analysis is right) when ACK is really missing from the low level hardware(it
happens under poor environment, right?)

Any advice is really appreciated !



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