Hi,
I was not near my working PC so I could not show any real code.
As far as I understand if you set 0 timeout as soon as you exit the call back
that it was set in it and return to the LwIP context your function will be
called !
When you work with RAW API, everything is running under one task (if you have
an OS)
Or in the same context. I am not sure how it works when you do not have an OS
because
I did not work without it.
Any way the TCP stack is doing some housekeeping: responding to ACK, sending
ACK, SYN etc…
Whenever you get a packet and the TCP stack call’s your recv callback the TCP
stack is not running
until you exit from the callback. Once you exit from the callback the TCP stack
returns to do its own
housekeeping… If you set a timer it starts to run after you exit the callback.
What can you do with the sys_timeout function… Lets assume that you get 300
bytes of data
and you need to process it… In recv callback you get the data, transfer it to a
buffer and raise a flag to let
main handle the new data. Once main finished processing the data it can set
another flag.
At the TCP stack you can set a timer at say 50ms… every 50ms it will call your
timer callback function:
Define a function like this:
static void TcpDealyedSendHandler(void *arg)
{
// does something
IF data ready then process it and if needed, send it using tcp_write…
ELSE start the timer again
sys_timeout( 50, TcpDealyedSendHandler, NULL);
}
.
.
In your recv or any other callback set the timeout
sys_timeout( 50, TcpDealyedSendHandler, NULL);
The above is just pseudo code to illustrate what I mean
BR,
Noam.
From: lwip-users [mailto:lwip-users-bounces+noam=silrd....@nongnu.org] On
Behalf Of Norbert Kleber
Sent: Sunday, September 25, 2016 2:15 PM
To: lwip-users@nongnu.org
Subject: Re: [lwip-users] prioritizing of active connections
Hi,
regarding the dirty trick I must admit I fear that it might cause a glitch
thats right. I put it in eitherway as a proof of concept and running
performance tests for evaluation of what might be possible. Since its a thesis
i thought of investigating the delay and the impact on the performance. For
actual use it shouldn't be in the code!
Since I am messing with the TCP timer I suppose that it can cause
earlier/unwanted retransmissions and connection timeouts. For my application
both doesn't pose to much of a threat at this point.
Regarding the suggest function if i understand it right i just set it up within
a callback function and if the
sys_check_timeouts();
function is called and the localtime compared to the time when i set it up
exceeds the intervall the function will be called. On that matter is it
possible to assign 0 as intervall value so it will be called with the next
sys_check_timeouts() ?
Also I want to say thank you for all your help.
sincerly,
Norbert
Am 24.09.2016 um 14:58 schrieb Noam Weissman:
Hi,
Doing some "dirty" trick will not help but cause other problems. IwIP can
back-fire and
you will get unpredictable results. Problems that can be difficult to find.
sys_timeout is an LwIP function that runs inside the context of LwIP. Time
interval is in milliseconds.
That means that if you set it to 100ms it will call your function (only once)
when time elapses.
So instead of using the poll call back that is triggered at best every 0.5
seconds ... you can set your
own timeout function that will handle some house keeping at a faster rate. Do
remember that if you
need it to periodically do something you need to set it again and again...
until you finish the process.
BR,
Noam.
________________________________
From: lwip-users
<lwip-users-bounces+noam=silrd....@nongnu.org><mailto:lwip-users-bounces+noam=silrd....@nongnu.org>
on behalf of Norbert Kleber
<norbert.kle...@student.fh-kiel.de><mailto:norbert.kle...@student.fh-kiel.de>
Sent: Saturday, September 24, 2016 11:20 AM
To: lwip-users@nongnu.org<mailto:lwip-users@nongnu.org>
Subject: Re: [lwip-users] prioritizing of active connections
Hi Noam,
thank you for your suggestion. I guess I will start with an OS for the next
project. For this one it's allready to late I am afraid (thesis due date next
month). I didn't fully understand the explanation in the wiki regarding the
sys_timeout(TMR_INTERVAL, function , NULL); function. Which timer triggers this
function and how can i calculate the exact timing of the sys_timeout?
For now i found an quick and dirty approach which i can't recommand to anyone.
I just call 2x tcp_tmr() directly after my computing work is done. This
improves my performance. Where i needed 36 seconds for one run I now only need
16 seconds.
sincerly,
Norbert
Am 23.09.2016 um 18:30 schrieb Noam Weissman:
Hi Norbert,
First of all I would suggest changing your design and use an OS. I am running
FreeRTOS
on STM micro's for 6 years now and I do not see myself doing it any other way.
The STM32F4 is a strong micro with sufficient power to do much more then you do
now.
If you run an OS there will be a small overhead but your system design will be
much simpler
to menage.
If you use Socket API you can send data outside of the LwIP context. If you use
RAW API
you cannot send data from outside of the LwIP context and must take that into
consideration:
First option protect the code that is called from outside of the LwIP context.
Either by using a
critical section (OS).... or using the poll call back.... or triggering LwIP
own system_timer call-back:
sys_timeout(TMR_INTERVAL, function , NULL);
The above is an LwIP internal timer handling. You pass the function you want
(see prototype)
with or without parameters and it will be triggered when time expires.
BR,
Noam.
________________________________
From: lwip-users
<lwip-users-bounces+noam=silrd....@nongnu.org><mailto:lwip-users-bounces+noam=silrd....@nongnu.org>
on behalf of Norbert Kleber
<norbert.kle...@student.fh-kiel.de><mailto:norbert.kle...@student.fh-kiel.de>
Sent: Friday, September 23, 2016 6:58 PM
To: lwip-users@nongnu.org<mailto:lwip-users@nongnu.org>
Subject: [lwip-users] prioritizing of active connections
Hi evereyone,
I got some questions again.
I am using the lwIP on a STM32F4 mikrocontroller without OS. A client
will connect to the stack at two ports for transmission. First port will
be used for controlsignals and second for datatransmission. The whole
System works sequentially.
Firstly 1 package will be received on the ctrl connection afterwards we
receive many packages on the dataconnection. Now I was wondering that
the stack acknowlegded all data packages before he acknowledges the ctrl
package. Due to the operation of the µC I can tell that he received the
package right away and ofcause i use the acknowledgement function in the
receive function. But somehow it is severly delayed approx. 200ms but
the later received data packages all get acknowledged right away.
Does the stack some prioritizing between open connections? Or is it due
to the Ctrl Package being quite short?
Also I am doing some computational work outside of the callback
functions and want to transmit some of the results asap over the ctrl
connection. Is there a way to do that without waiting for the polling
function? Or is there a way to trigger the polling function somehow for
a instant call? Also it seemed like i can't use tcp_write if i am
outside of a callback function (i was storing the pointer to the pcb in
a global variable).
sincerly,
Norbert
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