Re: [lwip-users] tcp client build up the connection slowly with the server

[address@hidden]

Am 25.06.2019 um 16:19 schrieb koszo.simon:
> I created my own http client based on the example which is in the answer of
> this question:
> https://stackoverflow.com/questions/26192758/how-can-i-send-a-simple-http-request-with-a-lwip-stack


You created your own http client? Why don't you use the one coming with
lwIP? (And yes, I'm too lazy to open that stackoverflow thing...)

> It works well, however I am not satisfied with the speed of the building up
> of the tcp connection. I printed out the value of a millisecond counter when
> the tcp_setup() function was called and when the connectCallback() function
> was called. The difference between the values are usually around 280 ms
> which is much bigger than I expected (less then 50 ms).
>
> What do you think? Is my expactation unrealistic? Or: Is there some problem
> with the network/server/lwip?

Ehrm, that depends on *so* many factors. On a local network with a
decent embedded system (e.g. Cortex-M around 50 MHz or more), a
connection time of ~1ms should be normal, so yes, you seem to have a
problem.

> I have tried to connect to three different servers running on different
> computers in the network, but the statistisc were the same. So I firstly
> suspect lwip...

Why do people always search for problems in other people's work? As I've
written above, lwIP is perfectly capable of much faster connection setup
than you even thought. This is not an lwIP problem but rather a problem
of your setup (or whoever you got your setup from). And by setup I mean
the OS port, CPU port, netif driver, etc.

Regards,
Simon