Re: [lwip-users] lwip reply delayed after long communication idle time

[Jochen Strohbeck]

Still guessing what leads to (some) delays in a (http) reply.

In the screenshot, http com starts (time 0, frame 78162) with SYN.
Then, I see a TCP Retransmission (time 3.0, frame 78164).
Between SYN and TCP Retransmission is a UDP broadcast
(frame 78163 in the screenshot, frame 1289 in the truncated log, 
not in screenshot due to view filter).

In the debug log, the message "TCP connection request 51360 -> 80." is
recorded,
followed by "try to resolve it; send out ARP request".
Note, both have the same timestamp and are therefore processed in a second.

Questions:

To me, it seems the LWIP  ARP negotiation is started by the TCP
Retransmission, not by SYN as usual (see frame 1021 in the wireshark trace).
Why?

Is it possible that the UDP broadcast can cause such a delay? DHCP is
enabled in LWIP,
therefore UDP is enabled too, although static IP is used.
If so, which component of LWIP does or has to process the UDP message?

P.S. The http request sets the timestamp of the log, just for those who
wonder why the timestamp goes back in time at 11:05:58. 

rtc_update_delayed.PNG
<http://lwip.100.n7.nabble.com/file/t1988/rtc_update_delayed.PNG>  
rtc_update_delayed_part.pcap
<http://lwip.100.n7.nabble.com/file/t1988/rtc_update_delayed_part.pcap>  




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