[lwip-users] enqueing problem

Hi all,

I have a problem that I have seen lots or users straggling with, but without any real solution.

I am trying to send data in a loop. I have triad closing NAGLE as follows:

// this should shut down the NAGLE algorithm

pcb->flags |= TF_NODELAY | TF_ACK_NOW;

I am calling tcp_output() on every tcp_write() but this does not help as well. I got ERR_MEM

after the 20^th something call to tcp_write()

I managed to find in one of the answers here that I should use a smaller window, meaning

change the settings in lwipopts.h… So I did, and it was a bit better.

/* TCP Maximum segment size. */

//#define TCP_MSS 1460

#define TCP_MSS 512

/* TCP sender buffer space (bytes). */

//#define TCP_SND_BUF (3*TCP_MSS)

#define TCP_SND_BUF (8*TCP_MSS)

Well the above helped and I was able to send more small packets but after 32 instead of 20 it again

It stopped sending and I got ERR_MEM.

The most important thing is when I check wireshark I see that the stack is sending all my data in one

Frame ???

Now can someone explain what is going on ?

For every call to tcp_write the enqueue mechanism is advancing snd_queulen by one !

I see two problems here. If the stack eventually sends all these in one TCP packet why is snd_queulen incremented at all ??

Secondly if I use pcb->flags |= TF_NODELAY why is the stack adding all the data into one packet ??

Your input is more than welcomed.

BR,

Noam.