RE: [lwip-users] raw interface, detecting retries

[Goldschmidt Simon]

Hi,

TCP retransmissions are taken care of internally, there is no need to care 
about this in your application code. Once the (possibly retransmitted) data is 
acked, tcp_sent will be called. As to tcp_poll, I don't remember exactly, but I 
think it is always called, no matter which state the tcp_pcb is in...

Simon

-----Ursprüngliche Nachricht-----
Von: address@hidden [mailto:address@hidden Im Auftrag von address@hidden
Gesendet: Mittwoch, 20. Februar 2008 12:22
An: address@hidden
Betreff: [lwip-users] raw interface, detecting retries

Moin all,

I use the raw interface to xmit some lengthy data over TCP. My applications 
works fine so far.

I have difficulties to implement retries in case of lost datagrams.

tcp_write sends data without copying it. The data is kept until tcp_sent 
callback notes success. Thereafter more data is prepared and xmitted.

What happens if the data gets lost? I expect tcp_sent will not be called as the 
other side did not acked it. After a while the tcp_poll callback will be 
called, which in turn could retransmit the data.

Nevertheless I see tcp_poll callback even when everything works fine.

How can I differentiate whether a retransmit is required or more data should be 
send?

Did I miss something in the docs? Any help apreciated.

Friedrich



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