HI simon:
I found the tcp_sndbuff always return 0 because of tcp_write fails. I think
memory allocate fail, it works well after I remove #define MEMP_MEM_MALLOC
1 from lwipopt.h
err = tcp_write(pcb, fsd->fifo.buffer + i, (u16_t)(fsd->fifo.size - i),
TCP_WRITE_FLAG_COPY);
if (err != ERR_OK)
{
return;
}
Does it make sense ?
Vincent Cui
Software Engineer Leader
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From: [email protected]
[mailto:[email protected]] On Behalf Of
[email protected]
Sent: 2012年4月13日 2:05
To: Mailing list for lwIP users
Subject: Re: [lwip-users] tcp_sndbuf return 0 when sending file
vincent cui wrote:
All
I develop a FTP server with lwIP 1.3.2 in Cortex M3 platform, when I use
FlashFXP to get file from the server, the tcp_sndbuf always return 0 after work
a while .
I capture it with wireshark, the file is attached file. The server ip:
192.168.1.51. it seems that transfer error and need retransmission.
From the wireshark capture, I cannot see why the segment is retransmitted.
Also, at which point do you get tcp_sndbuf==0, and what's the size of
tcp_sndbuf initially?
I'm afraid that doesn't really help on your problem, though :-(
If I were you, I'd first have a look at lwip_stats to see if there are dropped
segments or memory (allocation) failures and then monitor the value of
tcp_sndbuf() (maybe it keeps getting smaller and never grows again?).
My sendcode in server is below:
[..]
err = tcp_write(pcb, fsd->fifo.buffer + i, (u16_t)(fsd->fifo.size -
i), 1);
Yikes! Using numbers instead of constants is really a thing people should learn
(I'm speaking of TCP_WRITE_FLAG_COPY vs. '1')!
We provide the constants for people to use them so we are free to modify what
they are defined to. By using '1' instead of TCP_WRITE_FLAG_COPY, you have
successfully made your code susceptible to problems with future versions of
lwIP (once we decide to change the value of TCP_WRITE_FLAG_COPY) :-)
Simon
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