[lwip-users] Re: [lwip] TCP xfer stops

[Kieran Mansley]

On Tue, 26 Nov 2002, Atanas Korchev wrote:

> I'm using lwip 0.5.3 multithreading. I'm trying to receive a 1.7 MB file
> using BSD sockets library function lwip_recv. Xfer is running fine but
> sometimes stops in the middle, waiting for more data to come but the
> sender application (win32 prog) claims that all data has been sent. I
> sniffed all communication using ethereal and realised that liwp was ACK-
> ing one single segment four to five times!

This should be expected every now and then, it just means that a packet
has been lost, and the receiver is signifying this to the sender by not
acking new data.  Either that, or it is sending a window update.  There
was a bug that could cause the sender to stop sending data during large
transfers, and I expect this is what you are seeing:

http://www.sics.se/mailing-lists/lwip.html/msg01503.html

The fix is included in CVS on savannah, but you could easily add it to
your current checkout if you didn't want to change everything at the
moment.

Kieran

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