Hi simon:
When I receive tcp packet from client, I found that tcp payload is 970 and 490
by calling following code
for (q = p; q != NULL; q = q->next)
{
UINT len;
printf(" tcp payload len : %d \n", q->len);
f_write(fsd->fil, q->payload, q->len, &len);
tot_len += len;
if (len != q->len)
break;
}
And TCP_MSS is (1500 �C 40). So tcp received packet maximum data is 1460 (970
+ 490),
I wonder to know that there is a way to extend the value ? change TCP_MSS to
2048 ?
Vincent Cui
Software Engineer Leader
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200233
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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