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

From: Bill Auerbach
Subject: Re: [lwip-users] How to check send state?
Date: Tue, 16 Sep 2014 09:43:49 -0400



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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