I forgot the attachment. Sorry.
With kind regards,
Martin Datzmann
Von: Martin Datzmann
Gesendet: Montag, 15. Februar 2016 13:37
An: 'address@hidden'
Betreff: Acknowledge Problem
Dear all,
In my application I want to serve a webpage with 2 pictures
à 3 TCP-Ports necessary.
Sometimes it works well, but sometimes there is a sending Problem (tcp_out.c ?) with the pictures.
You can see the mistake in the screen-shot of the wireshark-recording.
After opening the connection, the webserver (192.168.115.74) usually sends 2 data packages and gets for them one ACK from the client (192.168.115.76) (eg. No. 706-708). Then the next 2 packages are sent.
Unfortunately sometimes one of the two sended packets is not removed from the unacknowledged-list.
In tcp_in.c in the function tcp_receive the while-loop (see below) is passed only once, although 2 packages where sent and acked.
-------------------------------------------------------------
/* Remove segment from the unacknowledged list if the incoming
ACK acknowlegdes them. */
while ((pcb->unacked != NULL &&
TCP_SEQ_LEQ(ntohl(pcb->unacked->tcphdr->seqno) +
TCP_TCPLEN(pcb->unacked), ackno))) {…}
-------------------------------------------------------------
The reason is, that for the second packed the pointer pcb->unacked is NULL.
Do you have an idea, what is the reason for this missing reference?
Mit freundlichen Grüßen
With kind regards,
Martin Datzmann
Softwareentwicklung
M&P motion control and power electronics GmbH
Bismarckstr. 56
01257 Dresden
Tel.: +49 (0)351 32 33 05 26
Fax.: +49 (0)351 32 33 05 19
Internet:
www.powerelectronics.de
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