Re: [lwip-users] Query amount of free buffers

[address@hidden]

Marco Jakobs wrote:
> OK ... good to know. :-) But i see no advantage to rewrite it from the
> netconn API to the socket API, as everything works fine
No, just wantet to make this clear for anyone having to decide between 
the 2 APIs.
> So the calculation of TCP_SND_QUEULEN will result in 8. Does this mean
> that TCP may use 8 out of 16 (MEMP_NUM_PBUF) buffers?
>    
Not really. TCP_SND_QUEUELEN == 8 says that at maximum, 8 pbufs will be 
queued for sending per TCP pcb. However, (up to CVS HEAD) every call to 
netconn_write creates 1 pbuf (PBUF_RAM when telling the stack to copy 
the data) or 2 pbufs (one PBUF_RAM and one PBUF_REF, when not telling 
the stack to copy the data) at minimum. Only the PBUF_REF pbufs come 
from the pool specified by MEMP_NUM_PBUF. The PBUF_RAM pbufs are 
allocated on the heap, the size of which is defined by MEM_SIZE.

Simon