Re: [lwip-users] TCP listen fucntion always return <=0

[Kieran Mansley]

On Fri, 2009-09-18 at 11:28 +0200, Oscar F wrote:
> Ok, sorry. The values are always the same
> 
> MEMP_NUM_NETCONN        4
> errno = 0

You have two problems.  First, MEMP_NUM_NETCONN limits how many sockets
you can have, so in your example this needs to be at least 8, and more
if you want sockets to send/recv data on as well as just listening.  I
would suggest 16 as a minimum.

> but i saw maybe the problem
> /* MEMP_NUM_TCP_PCB: the number of simultaneously active TCP
> connections. */
> #define MEMP_NUM_TCP_PCB        2
> /* MEMP_NUM_TCP_PCB_LISTEN: the number of listening TCP connections.
> */
> #define MEMP_NUM_TCP_PCB_LISTEN 1
> /* MEMP_NUM_TCP_SEG: the number of simultaneously queued TCP segments.
> */
> #define MEMP_NUM_TCP_SEG        9
> /* MEMP_NUM_SYS_TIMEOUT: the number of simulateously active timeouts.
> */
> #define MEMP_NUM_SYS_TIMEOUT    6
> 
> 
> #define MEMP_NUM_TCP_PCB_LISTEN 1  can be possible? i´ll test

Yes, that will need to be at least as big as the number of listening
sockets, so 8 as a minimum.  MEMP_NUM_TCP_PCB will need to be bigger too
as you need one of these for each data socket (so again 8 would be
sensible minimum) and I would suggest that having just 9 TCP segments
for 8 connections is cutting things pretty small: 16 or 32 would be
better, but you may need more than that depending on how much data you
plan to send and receive.

You should have seen some warnings when running with the settings you
had if you had LWIP_DEBUG on - see lwip_sanity_check() function in
src/core/init.c  It's a good idea to do this when developing to show any
problems you have quickly and easily.

Thanks

Kieran