Problem
I successfully build and run a TLS client Example (picow_tls_client_background executable) from the GitHub, however a simple http GET request takes about 20 seconds. It does not actually depend on the server response: I tested server, that responds empty string at all, and server with about few kb output - no matter, it takes about 20 seconds to make a request.
As the result of debug, I understand, that 99% of the request time takes altcp_connect- before that, it takes several miliseconds, and after that, starting from the callback, i.e. tls_client_connected, it takes about millisecond until the request is made:
Pico turned on -- [few ms] -- altcp_connect() -- [19 sec] -- tls_client_connected() -- [1 ms] -- I see comleted incoming request on the server
Tried to solve
I made a reserch, I found that such behaviour, can be caused by lwIP configuration in lwipopts.h. It already sounds weird, because it probably should been tested by Raspberry Pi developers, who posted the code on GitHub.
So I set #define MEMP_SANITY_CHECK 0, set
#define LWIP_DEBUG 0
#define ALTCP_MBEDTLS_DEBUG LWIP_DBG_OFF
I also tried to reduce TCP_WND or\and TCP_MSS, but any signficant changes produced cmake errors, that something overflows something. However, I reduced a bit that values, without errors at building.
However, all of that actions did not change request time - it still the same.
I also tried (although, as I wroted, this step is passed fast) to connect to ip directly, instead of DNS resolving by hostname, and it still takes same long.
