libcurl failing to connect to server (testCurl.c)

[Kniggebrot]

Hello everyone,
I recently tried to run the testCurl.c on my ESP32-DevKitC (revision 1) to test the functionality of libcurl on said ESP, because I was looking for a library which is able to do SMTP- and IMAP-TLS-E-Mail-sending and receiving and libcurl seems quite suited for the job whilst also available on the ESP (thanks @nkolban for that!)

And although app and library compile without an error (after removing system_init()), cURL prints the following error:

• connect to 93.184.216.34 port 80 failed: Connection already in progress
• Failed to connect to example.com port 80: Connection already in progress
• Closing connection 0
  I (3342) main: curl_easy_perform failed: Couldn't connect to server

The full build & monitor log can be found here: https://pastebin.com/D9Ra0vdt

I used the latest cURL and ESP-IDF. I suspect it's an issue with the IDF since I tried various older versions...
Thank you for your time!

[danielRM88]

Hi @Kniggebrot have you had any luck with this? I am facing the same problem.

[Kniggebrot]

Hi @danielRM88, sorry for the late answer, had quite a busy week... Thus I didn't have much time to make further tests. I'll try to setup some older IDFs after Christmas, but I can't make any promises... Hopefully I don't need to go too many versions back :D

[paulreimer]

I have the same issue! I will note that it does work on the current esp-idf release (tag v2.1), but does not work on the latest master at this time.

I ran git bisect on esp-idf and determined this to be the first breaking commit (curl requests did work just before this):
espressif/esp-idf@3ebf792

It is completely broken after that commit and for the next few commits (boot loop with the following error:)

assertion "socket has no netconn" failed: file "/esp-idf/components/lwip/api/sockets.c", line 3143, function: lwip_socket_drop_registered_memberships
abort() was called at PC 0x40108323 on core 0
0x40108323: __assert_func at /Users/ivan/e/newlib_xtensa-2.2.0-bin/newlib_xtensa-2.2.0/xtensa-esp32-elf/newlib/libc/stdlib/../../../.././newlib/libc/stdlib/assert.c:63 (discriminator 8)
...

and then the behaviour changes later to the one reported in this issue (Connection already in progress) at this commit:
espressif/esp-idf@3f83914

I'm not sure how/where to fix it beyond that, unfortunately.

[paulreimer]

Alright well at least here is the minimal diff that broke it (I'll assume the middle commit 3ebf792 was WIP and the assertion "socket has no netconn" failed is a result of that)

espressif/esp-idf@a320fed...3f83914

[Mr-NVR]

See espressif/esp-idf#1452

Loboris gives an answer (until it's fixed), essentially:

• in curl/lib/select.h, the macro
  #define VALID_SOCK(s) (((s) >= 0) && ((s) < FD_SETSIZE))

• has to be changed to:
  #define VALID_SOCK(s) (((s) - LWIP_SOCKET_OFFSET >= 0) && ((s) - LWIP_SOCKET_OFFSET < FD_SETSIZE))

[Kniggebrot]

Oh nice! Works well, lots of thanks to you guys for helping!