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Re: [lwip-users] How to check send state?

From: Karl Karpfen
Subject: Re: [lwip-users] How to check send state?
Date: Wed, 17 Sep 2014 07:54:43 +0200

OK, so let me ask this in an different way:

Currently I do have data to be sent available in main loop only. How can I enqueue these data into the lwIP-ISR-context correctly so that it can be transmitted without problems?

Currently I'm doing it as described at http://lwip.wikia.com/wiki/Raw/TCPin section "Sending TCP data" which seems to be wrong for my case...

2014-09-16 17:20 GMT+02:00 Bill Auerbach <address@hidden>:

Yeah, I should have kept reading.  Sorry


From: lwip-users-bounces+bauerbach=address@hidden [mailto:lwip-users-bounces+bauerbach=address@hidden] On Behalf Of Simon Goldschmidt
Sent: Tuesday, September 16, 2014 9:51 AM
To: Mailing list for lwIP users
Subject: Re: [lwip-users] How to check send state?


Bill, I appreciate you trying to teach programming basics, but I think this won't get Karl Karpfen further: sending from main-loop and receiving in interrupt just won't work with lwIP.




Gesendet: Dienstag, 16. September 2014 um 15:43 Uhr
Von: "Bill Auerbach" <address@hidden>
An: "'Mailing list for lwIP users'" <address@hidden>
Betreff: Re: [lwip-users] How to check send state?



Did you declare sentLength as volatile?  You might also need to protect it if it’s not loaded/stored in a single processor instruction (not likely to be the case with a 32-bit architecture).




From: address@hidden [mailto:address@hidden] On Behalf Of Karl Karpfen
Sent: Monday, September 15, 2014 3:00 PM
To: address@hidden
Subject: [lwip-users] How to check send state?



within my lwIP application (TCP with permanent connection) I'm sending some data out of main-loop (no interrupt context) and start submission by calling


Sending of data is done via tcp_write(). Within the send function itself amount of data already sent is stored in a variable sentLength. Now to find out if it is possible to send next bunch of data I check this variable. When its size is equal to the length of the previous data buffer, sending was completed and I start submission of next buffer.


My problem here: sentLength is manipulated out of interrupt context while checking it for completion is done out of main loop. It seems this sometimes causes troubles, at receiver side I can see incomplete frames.

So my question: what is the correct way to find out if currentPcb has finished sending (or better has pushed all data to tcp_write()) and is ready to accept next bunch of data?


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