How to get large data from web page?

Partners & Sponsors ST
1

Hi, could someone tell me how to get large data from web page?
I’m using Netconn interface + lwip + FreeRTOS on stm32f407vg.

I tried to use a “taskENTER_CRITICAL();” and “taskEXIT_CRITICAL();” for stopping an “osKernelStart” during getting a large data …
But, it did not help!

Browser writes:
The connection was reset
During page download, the connection to the server was reset.
But ping works!

What am I doing wrong?

Below a code for obtaining data

...
if ((strncmp(buf, "POST /STM32F4xx.html", 20) == 0)
						|| (strncmp(buf, "POST / ", 7) == 0)) {
					/* Load STM32F4xx page */
					parse(buf); // 
					fs_open(&file, "/STM32F4xx.html");
					taskENTER_CRITICAL();
					printf("- taskENTER_CRITICAL - \n\r");
					netconn_write(conn, (const unsigned char* )(file.data),
							(size_t )file.len, NETCONN_NOCOPY);
					printf("- taskEXIT_CRITICAL - \n\r");
					taskEXIT_CRITICAL(); 
					fs_close(&file);
				} else { ...
2

taskENTER/EXIT_CRITICAL disable/enable (FrreRTOS covered) interrupts.
I doubt that netconn_write and likely also printf work with interrupts disabled.
Also critical sections are intended for a VERY SHORT period of time/code sequence to avoid disabling interrupts for a longer time for obvious reasons.
If you think that netconn_write isn’t working as expected I’d recommend to check the return values of functions called :wink:
Network traffic can be checked with Wireshark at least, maybe curl can be handy for http traffic testing.

4

Thank you for answer I don’t think that netconn_write isn’t working as extected this is the first thing that came to my mind, if I transfer a large amount of data from the web page …
Do you think I do not need to use the "taskENTER/EXIT_CRITICAL " and “NETCONN” itself can to process a large amount of data?

And second question about “Wireshak”:
Thanks for adviсe to use “Wireshak”!
You wrote to me need to check the return values of functions called…
I found out how to check that data the web page sends, see screen.
But, i don’t know how to check the return values of functions called in"Wireshak".
Could you help my find out in “Wireshak” how do I need to check the return values of called functions?

1
11917×1037 337 KB

5

You shouldn’t use critical sections for long lasting operations like transferring large amounts of data over network. Never ! And how should a critical section help there in any way ?
You should also check the lwIP API documentation of netconn_write regarding it’s return values (ok / error codes) and it’s behavior and potential limitations.
That’s what I meant with return values. The return values of the functions called in your code e.g. netconn_write, fs_open etc.
How do you know if the functions called were successful ?
However - it’s good and pretty useful using Wireshark to verify the data you intended to send back to the browser and the overall http protocol flow.

1 Like
6

“Get” request I can send about 30 times and after stm32 freezes up. The quantity of “Get” requests depends from “heap_size”!
And if send “POST” request stm32 freezes up at once!
Any ideas?

2
21920×1052 354 KB

7

Well, if the 1st problem depends on heap size there might be memory leak. Or sth. else.

And if send “POST” request stm32 freezes up at once!

That’s the easy one :slight_smile: Just use your debugger and follow the code … as we all do it.
Good luck :+1: