[lwip-users] TCP full-duplex communication problem

[pekez]

Hi guys,

me again, with new question. :)

On my client side (PC) right now I have two threads, one thread only 
sending, whreas other one is always receiving. Both threads work with 
same socket. On the server side (ZYNQ) I have the same thing, one thread 
receiving, while other is sending.

Now, when I test only one direction independently, let's say only 
sending from PC to ZYNQ, or vice verca sending from ZYNQ to PC, 
everything works fine. However, I need everything to work 
simultaneously, and when I let all threads start working, next thing 
happens: both threads on PC finish working as expected, while on the 
ZYNQ, one thread finish working as expected, most often the one that is 
sending, while the other one never receives all the data it is supposed 
to receive, as though the socket is closed or something (it's not, I 
checked carefully). Nothing is happening at all, I am looking in 
Wireshark, and there is just no communication at all after the first 
thread on the ZYNQ finish working.

I also tried to make two separate connections so that one direction 
(PC--->ZYNQ) is working over one socket, and other one (PC<---ZYNQ) over 
some other socket. This works much better, never have similiar problems 
on ZYNQ side, but really rarely even in this case, communication stops 
working, but this time the problem seems to be PC side, again when one 
thread finish before the other, I am getting some kind of strange 
messages in Wireshark, such as "tcp acked unseen segment".

I have made referent server application for PC, and when communication 
is PC to PC, everything is OK, so I assume that it's some kind of 
problem with lwIP, which can be solved maybe by changing some options in 
lwipopts.h (I hope it's only that :) ). I guess is hard to help with 
only this much of information, but maybe someone has already faced 
similar problems.

I am working with Socket API, lwIP v1.4.1 with FreeRTOS v8.2.3.

Best regards,
and thanks in advance.


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