lwIP on STM32F1: tcp_accept callback function is not called

Question

I am going to setup lwIP on STM32f107RCT6 and DP83848. I used CubeMX to generate primary code. After downloading the code into MCU with command ping and arp –a the result is:
(MCU IP: 192.168.1.57 * Subnet: 255.255.255.0 * GW:192.168.1.1 *** MAC: 00-80-e1-00-00-00)

C:\Users\GmtK>ping 192.168.1.57

Pinging 192.168.1.57 with 32 bytes of data:  
Reply from 192.168.1.11: Destination host unreachable.  
Reply from 192.168.1.11: Destination host unreachable.  
Reply from 192.168.1.11: Destination host unreachable.  
Reply from 192.168.1.11: Destination host unreachable.  

Ping statistics for 192.168.1.57:
    Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),



C:\Users\GmtK>arp -a

Interface: 192.168.1.11 --- 0x16  
  Internet Address      Physical Address      Type  
  192.168.1.1           74-da-da-64-6a-59     dynamic  
  192.168.1.7           2c-fd-a1-5c-3e-99     dynamic  
  192.168.1.255         ff-ff-ff-ff-ff-ff     static  
  224.0.0.22            01-00-5e-00-00-16     static  
  224.0.0.251           01-00-5e-00-00-fb     static  
  224.0.0.252           01-00-5e-00-00-fc     static  
  239.255.255.250       01-00-5e-7f-ff-fa     static  
  255.255.255.255       ff-ff-ff-ff-ff-ff     static

However by resetting the MCU and again using arp –a:

C:\Users\GmtK>arp -a

Interface: 192.168.1.11 --- 0x16  
  Internet Address      Physical Address      Type  
  192.168.1.1           74-da-da-64-6a-59     dynamic  
  192.168.1.7           2c-fd-a1-5c-3e-99     dynamic  
  192.168.1.57          00-80-e1-00-00-00     dynamic   //this my MCU   
  192.168.1.255         ff-ff-ff-ff-ff-ff     static  
  224.0.0.22            01-00-5e-00-00-16     static  
  224.0.0.251           01-00-5e-00-00-fb     static  
  224.0.0.252           01-00-5e-00-00-fc     static  
  239.255.255.250       01-00-5e-7f-ff-fa     static  
  255.255.255.255       ff-ff-ff-ff-ff-ff     static

This cycle is repeated and by resetting the MCU it returns to the list provided by arp -a command. I reckon that the ping command is somewhat understandable why it not work. Because maybe it is not implemented by lwIP. So I used Hercules TCP Client with

Madule IP = 192.168.1.57 and Port = 7

And pressed Connect button. The outcome was:

Connecting to 192.168.1.57 ...  
TCP connection timeout

I have employed two LEDs to debug it and since the RUNNING_LED is turned on the tcp_echoserver_init() is executed. However, AUX_LED never has been turned on meaning tcp_echoserver_accept() callback function never is called! What is the problem? Why it is not called?

This is my code which adopted from ST TCP ECHO SERVER example:

/**
  * @brief  Initializes the tcp echo server
  * @param  None
  * @retval None
  */
void tcp_echoserver_init(void)
{
  /* create new tcp pcb */
  tcp_echoserver_pcb = tcp_new();

  if (tcp_echoserver_pcb != NULL)
  {
    err_t err;
    /* bind echo_pcb to port 7 (ECHO protocol) */
    err = tcp_bind(tcp_echoserver_pcb, IP_ADDR_ANY, 7);

    if (err == ERR_OK)
    {

      /* start tcp listening for echo_pcb */
      tcp_echoserver_pcb = tcp_listen(tcp_echoserver_pcb);

      /* initialize LwIP tcp_accept callback function */
      tcp_accept(tcp_echoserver_pcb, tcp_echoserver_accept);
      HAL_GPIO_WritePin(RUNNING_LED, 0);  //RUNNING_LED Will be turned on here
    }
    else 
    {
      /* deallocate the pcb */
      memp_free(MEMP_TCP_PCB, tcp_echoserver_pcb);

    }
  }
}

/**
  * @brief  This function is the implementation of tcp_accept LwIP callback
  * @param  arg: not used
  * @param  newpcb: pointer on tcp_pcb struct for the newly created tcp connection
  * @param  err: not used 
  * @retval err_t: error status
  */
static err_t tcp_echoserver_accept(void *arg, struct tcp_pcb *newpcb, err_t err)
{
  HAL_GPIO_WritePin(AUx_LED, 0);  //AUX_LED will be turned on here
  err_t ret_err;
  struct tcp_echoserver_struct *es;
  LWIP_UNUSED_ARG(arg);
  LWIP_UNUSED_ARG(err);

  /* set priority for the newly accepted tcp connection newpcb */
  tcp_setprio(newpcb, TCP_PRIO_MIN);

  /* allocate structure es to maintain tcp connection informations */
  es = (struct tcp_echoserver_struct *)mem_malloc(sizeof(struct tcp_echoserver_struct));
  if (es != NULL)
  {
    es->state = ES_ACCEPTED;
    es->pcb = newpcb;
    es->retries = 0;
    es->p = NULL;

    /* pass newly allocated es structure as argument to newpcb */
    tcp_arg(newpcb, es);

    /* initialize lwip tcp_recv callback function for newpcb  */ 
    tcp_recv(newpcb, tcp_echoserver_recv);

    /* initialize lwip tcp_err callback function for newpcb  */
    tcp_err(newpcb, tcp_echoserver_error);

    /* initialize lwip tcp_poll callback function for newpcb */
    tcp_poll(newpcb, tcp_echoserver_poll, 0);

    ret_err = ERR_OK;
  }
  else
  {
    /*  close tcp connection */
    tcp_echoserver_connection_close(newpcb, es);
    /* return memory error */
    ret_err = ERR_MEM;
  }
  return ret_err;  
}

Yes, since Raw API implementation works in polling mode, it needed to add some lines in infinite loop. — GntS
how did you solve please help, I have a same problem. What does it mean "some lines" ? — NetworkStudent
@NetworkStudent, sorry for being late. I already answered my question, hoping help you. — GntS

GntS GntS · Accepted Answer · 2021-01-30T05:32:46

As I mentioned in my comment, Raw API implementation works in polling mode so you have to ensure continuous software polling whether a new packet is received or not. As far as I can remember I added these two lines to my code at body of infinite loop:

  while (1)
  {
    ethernetif_input(&gnetif);
    sys_check_timeouts();
  }

for more details please read through the informative user manual provided by ST, UM1713.

lwIP on STM32F1: tcp_accept callback function is not called

1 Answers