[lwip-users] stm32: do I have to call tcp_write() even on error?

[bruzzi]

Hello,

I impelmented modbus over tcp using LwIP library. In case of modbus protocol
error i don't call tcp_write() function, is that correct?

This is my callback function on received packet. 
static void modbusserver_send(struct tcp_pcb *tpcb, struct
modbusserver_struct *es)
{
  struct pbuf *ptr;
  err_t wr_err = ERR_OK;
  
  while ((wr_err == ERR_OK) &&
         (es->p != NULL) && 
         (es->p->len <= tcp_sndbuf(tpcb)))
    {
    
      /* get pointer on pbuf from es structure */
      ptr = es->p;

      if (wr_err == ERR_OK)
        {
          u16_t plen;

          plen = ptr->len;

          if (plen > PROTO_TRAMA_LEN) memcpy(ProtoStatus[PROTO_TCP].InBuf,
ptr->payload, PROTO_TRAMA_LEN);
          else memcpy(ProtoStatus[PROTO_TCP].InBuf, ptr->payload, plen);
        
          /* enqueue data for transmission */
          if (Proto_Modbus_Main_TCP(PROTO_TCP) == 0) wr_err = tcp_write(tpcb,
ProtoStatus[PROTO_TCP].OutBuf, ProtoStatus[PROTO_TCP].OutCounter, 1);

          /* continue with next pbuf in chain (if any) */
          es->p = ptr->next;
        
          if(es->p != NULL)
            {
              /* increment reference count for es->p */
              pbuf_ref(es->p);
            }
        
          /* free pbuf: will free pbufs up to es->p (because es->p has a 
reference
count > 0) */
          pbuf_free(ptr);
  
          /* Update tcp window size to be advertized : should be called when
received
             data (with the amount plen) has been processed by the application
layer */
          tcp_recved(tpcb, plen);
        }
      else if(wr_err == ERR_MEM)
        {
          /* we are low on memory, try later / harder, defer to poll */
          es->p = ptr;
        }
      else
        {
          /* other problem ?? */
        }
    }
}

Thanks and best regards

ms
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