Re: [lwip-users] TCP send problem

[Paul Webber]

Dominik,

 

I am doing about the same thing as you. Try the tcp_write (tpcb,&buff[flag],sendLen, TCP_WRITE_FLAG_COPY); TCP_WRITE_FLAG_COPY is defined as 0x01. I did not have success sending with 0. I am however using 1.4.1

 

Hope this helps,

 

Paul

 

 

From: lwip-users-bounces+address@hidden [mailto:lwip-users-bounces+address@hidden On Behalf Of Dominik Wybranczyk
Sent: Monday, August 18, 2014 4:46 AM
To: address@hidden
Subject: [lwip-users] TCP send problem

 

Hello, my name is Dominik and this is my first post to lwip mailing list. I am working on stm32f4 IOT project where I want to use RAW lwip. I am basing on standalone tcp echo example made for STM32F4DIS-BB (Embest). I have already designed some drivers, and they are working great (like connection accpet, connection close, receiving handler, parser etc). But I have some problems with sending data. Everything works well when I am sending messages up to 38B, but if I send more than they are corrupted. 

 

Here is how it works:

My device is server, and I connect as clinet with my PC. I am sending some data from PC to my device. Than when I have received some information form PC, I parse it and want to respond with another data.

Firstly I am checking "freespace" in sending container by using tbp_sndbuf() like:

freespace = tcp_sndbuf(tpcb);

Usually there are a lot of space (like 2500B, but I also have handler for the situation when there are more data to send than container can handle...) so after that I am passing message to tcp_write like this:

wr_err = tcp_write(tpcb,&buff[flag], sendLen,0);

Variable wr_err is always 0, so "mem write" is OK. After that to make sure the message will be send now I call:

tcp_output(tpcb);

 

Sadly, the information I am receivng on PC is wrong every time when I am sending more than 38B. Usually its shorter and the message is like: 

corrupted_data + SMALL_PART_THAT_IS_OK + other_corrupted_data.

 

To be honest I am not getting the idea with the tcp_send() callback, but I assume that I dont need it in this simple example.

 

I am using lwip_v1.3.2 as in example. Should I update it?

 

What should I look at? Am I doing something wrong?

Kind Regards

Dominik