Re: [lwip-users] Missing ACKs in Websocket echo server

[Mike He]

I've also attached a successful echo session with the server at 
echo.websocket.org for reference.

Thanks,
Mike


On 6/19/2014 9:22 AM, Mike He wrote:
> Hello,
>
> I am trying to write up a simple Websocket echo server on an embedded 
> device with lwip. Looking at the Wireshark traces, it appears that I 
> am missing ACKs from the server, but the Websocket handshake and 
> packets themselves seem to be well-formed.
>
> I think this is leading to failed behavior. The first issue is that 
> connection is inconsistent. Sometimes an error is returned, sometimes 
> the client seems to connect successfully. Then the second issue is 
> that after the client sends a simple test frame, the server responds 
> with an echo, but this echo is not picked up by the client.
>
> I've attached the wireshark trace, showing first a failed connection, 
> then a "successful" one, then a message and echo.
>
> If these problems are indeed due to missing ACK's, what am I doing 
> wrong in the tcp_recv callback? I do call tcp_recved(pcb, p->tot_len); 
> Is there something else I need to be doing?
>
> Thanks,
> Mike

Echo from echo.websocket.org.pcapng
Description: Binary data