Re: [lwip-users] Output fails when output size exceeds 14KB while using sockets

[DipSwitch]

On 01/17/2012 08:34 PM, Kieran Mansley wrote:
> It's not obvious what the problem is.  Which version of lwIP?
Thanks for your time! I forgot some essential info yeah, sorry about that.
I'm using LwIP v1.4.0 with a Tripple Speed Ethernet MAC driver modified 
for multi-tasking. The system is a Nios II core running on a Cyclone IV 
with 128MB of RAM so I wouldn't suspect any resource problems unless it 
would be somewhere in the MAC output buffer.

> Does the write() call return an error in the case when it doesn't work?
The problem is that the call to write never returns. 14KB works fine but 
as soon as I'm trying to send > 14KB or more it locks up and never 
returns (waited for like 5 minutes but than I got tired of waiting).


> Do you receive anything at the receiver?  Does anything make it on to the wire 
> (e.g. get a packet capture to see).
This code is part of an web server which sends the header line by line. 
The client system receives the HTTP headers, the clients TCP stack sends 
an acknowledge and then there is complete silence. Not one byte of the 
page content is send.

> I expect you are running out of a resource, but looking in your lwipopts 
> doesn't show anything that would cause a problem at 15KB.  The only odd thing I 
> noticed there is that your setting for LWIP_NUM_NETBUF depends on the number of 
> connections (it is the same as the definition of LWIP_NUM_NETCONN) which 
> doesn't really make sense, but the value it will be assigned from that 
> definition is around 54, so should be OK for sending 15 MSS of
Thanks for taking a look at the configuration file, good to know there 
is no true error there. I'll take a look at the LWIP_NUM_NETBUF tomorrow 
thanks!