problems establishing tcp connection with stm32h753

[Oskar-Tamm]

Hello! I'm fairly new to embedded development. I'm trying to turn my stm into an echoserver, but I'm having problems with it. I followed the tutorial and the provided github tcp example. In main.c "USER CODE BEGIN/END 0" Section, I have everything from the tcp example before the main function. Additionally I've defined mg_millis(), and mg_random() in that section as well. The main function itself is identical to the tcp example aside from stm initialisations. Here's a screenshot of the serial console:

All attempts to ping the board are succesful but when I try to connect (using hercules SETUP utility as client) then I get a "tcp connection error 10061". Doing a debug run, the first loop through the server event handler goes into the if branch with MG_EV_OPEN event and the loops after that don'. But it never goes into the if branch with MG_EV_READ. Any idea of what the problem could be, and how to fix it?

PS: here's the (relevant part of) my main.c:

#include "mongoose.h"
...
/* USER CODE BEGIN 0 */
static const char *s_lsn = "tcp://localhost:8765";   // Listening address
static const char *s_conn = "tcp://localhost:8765";  // Connect to address

// client resources
static struct c_res_s {
  int i;
  struct mg_connection *c;
} c_res;

int _write(int fd, unsigned char *buf, int len) {
  if (fd == 1 || fd == 2) {                     // stdout or stderr ?
    HAL_UART_Transmit(&huart3, buf, len, 999);  // Print to the UART
  }
  return len;
}

uint64_t mg_millis(void) {	//this is necessary for mongoose to properly function
  return HAL_GetTick();
}

// CLIENT event handler
static void cfn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
  int *i = &((struct c_res_s *) fn_data)->i;
  if (ev == MG_EV_OPEN) {
    MG_INFO(("CLIENT has been initialized"));
  } else if (ev == MG_EV_CONNECT) {
    MG_INFO(("CLIENT connected"));
    if (mg_url_is_ssl(s_conn)) {
      struct mg_tls_opts opts = {.ca = mg_unpacked("/certs/ss_ca.pem"),
                                 .cert = mg_unpacked("/certs/ss_client.pem"),
                                 .key = mg_unpacked("/certs/ss_client.pem")};
      mg_tls_init(c, &opts);
    }
    *i = 1;  // do something
  } else if (ev == MG_EV_READ) {
    struct mg_iobuf *r = &c->recv;
    MG_INFO(("CLIENT got data: %.*s", r->len, r->buf));
    r->len = 0;  // Tell Mongoose we've consumed data
  } else if (ev == MG_EV_CLOSE) {
    MG_INFO(("CLIENT disconnected"));
    // signal we are done
    ((struct c_res_s *) fn_data)->c = NULL;
  } else if (ev == MG_EV_ERROR) {
    MG_INFO(("CLIENT error: %s", (char *) ev_data));
  } else if (ev == MG_EV_POLL && *i != 0) {
    switch ((*i)++) {
      case 50:  // 50 x 100ms = 5s
        mg_send(c, "Hi, there", 9);
        MG_INFO(("CLIENT sent data"));
        break;
      case 100:  // another 5s
        // send any possible outstanding data and close the connection
        c->is_draining = 1;
        break;
    }
  }
}


// SERVER event handler
static void sfn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
  if (ev == MG_EV_OPEN && c->is_listening == 1) {
    MG_INFO(("SERVER is listening"));
  } else if (ev == MG_EV_ACCEPT) {
    MG_INFO(("SERVER accepted a connection"));
  } else if (ev == MG_EV_READ) {
    struct mg_iobuf *r = &c->recv;
    MG_INFO(("SERVER got data: %.*s", r->len, r->buf));
    mg_send(c,"Client received Data :",23);
    mg_send(c, r->buf, r->len);  // echo it back
    r->len = 0;                  // Tell Mongoose we've consumed data
  } else if (ev == MG_EV_CLOSE) {
    MG_INFO(("SERVER disconnected"));
  } else if (ev == MG_EV_ERROR) {
    MG_INFO(("SERVER error: %s", (char *) ev_data));
  }
  (void) fn_data;
}

bool mg_random(void *buf, size_t len) {  // Use on-board RNG
  for (size_t n = 0; n < len; n += sizeof(uint32_t)) {
    uint32_t r;
    HAL_RNG_GenerateRandomNumber(&hrng, &r);
    memcpy((char *) buf + n, &r, n + sizeof(r) > len ? len - n : sizeof(r));
  }
  return true;
}


// Timer function - recreate client connection if it is closed
static void timer_fn(void *arg) {
  struct mg_mgr *mgr = (struct mg_mgr *) arg;
  if (c_res.c == NULL) {
    c_res.i = 0;
    c_res.c = mg_connect(mgr, s_conn, cfn, &c_res);
    MG_INFO(("CLIENT %s", c_res.c ? "connecting" : "failed"));
  }
}



/* USER CODE END 0 */

/**
  * @brief  The application entry point.
  * @retval int
  */
int main(void)
{

  /* USER CODE BEGIN 1 */

  /* USER CODE END 1 */

  /* MPU Configuration--------------------------------------------------------*/
  MPU_Config();

  /* MCU Configuration--------------------------------------------------------*/

  /* Reset of all peripherals, Initializes the Flash interface and the Systick. */
  HAL_Init();

  /* USER CODE BEGIN Init */

  /* USER CODE END Init */

  /* Configure the system clock */
  SystemClock_Config();

  /* USER CODE BEGIN SysInit */

  /* USER CODE END SysInit */

  /* Initialize all configured peripherals */
  MX_GPIO_Init();
  MX_ETH_Init();
  MX_RNG_Init();
  MX_USART3_UART_Init();
  /* USER CODE BEGIN 2 */

  struct mg_mgr mgr;        // Mongoose event manager
  struct mg_connection *c;
  mg_mgr_init(&mgr);        // Initialise event manager
  mg_log_set(MG_LL_DEBUG);  // Set log level to debug
  mg_timer_add(&mgr, 15000, MG_TIMER_REPEAT | MG_TIMER_RUN_NOW, timer_fn, &mgr);
  c=mg_listen(&mgr,s_lsn,sfn,NULL);
  /* USER CODE END 2 */

  /* Infinite loop */
  /* USER CODE BEGIN WHILE */
  if (c == NULL) {
    MG_INFO(("SERVER cant' open a connection"));
    return 0;
  }
  while (1)
  {
	  mg_mgr_poll(&mgr, 100);
  }
    /* USER CODE END WHILE */
  mg_mgr_free(&mgr);
  return 0;
    /* USER CODE BEGIN 3 */
}

PPS: I've done everything with STM32CubeIDE

[scaprile]

Please do not post screen captures, post text logs.
Please do not post your whole program, we don't check user code for errors, if you have a problem, ask specific questions and post those sections where you are in doubt.
Please don't throw pieces of code here and there and then ask us why it doesn't work. It is impossible to understand why what you want to do is not working if you don't say what you want to do.

Said that, to the best of my guessing, you have copied a piece of code that is intended to work on an operating system where both client and server run on the same host and use the loopback interface provided by the OS. You pasted that code into an embedded system with no OS, where there is no loopback interface.
Your first problem is that you open a server on a non-existent internal interface and expect to reach that server from the outside world.
Your second problem is that you expect to get a data event without a connection event first. You are trying to run a TCP server but apparently don't realize that TCP needs to connect first, thing that your client is telling you that did not succeed, obviously, because there is no server at that address. In your log, which I can't reproduce here because you posted a screen capture, there can be seen, clearly, that it is listening on 127.0.0.1, which is 'localhost', but there is no such interface on a baremetal system, nor is your code listening on your IP, hence rejecting your TCP connection request
I suggest you sniff your network (using Wireshark, for example) and observe the traffic, so you can understand what you are doing, and read about networking. Unfortunately it is not our function nor we have the time to explain to you all that.
There are other weird things in your log, too.

From the back of my mind, I would change 'localhost' for '0.0.0.0', which means "listen in all interfaces", and is shown and explained in most of our embedded tutorials. Then you can expect to get a CONNECT event first, then when your connecting client sends any data, you will see a DATA event

Please see our documentation, and follow the guidelines in our tutorials.