TM4C129ENCPDT: how to send data from client to server over ethernet without opening new connection/(same socket)

Hi,

  Do you see the same connection issue if you run the client example in this app note  https://www.ti.com/lit/pdf/spna248?

  I'm not sure where your code from. It is very similar to example by STMicroelectronics. If this is the case, please read their license agreement 

/**
  ******************************************************************************
  * @file    tcp_echoclient.c
  * @author  MCD Application Team
  * @version V1.1.0
  * @date    31-July-2013 
  * @brief   tcp echoclient application using LwIP RAW API
  ******************************************************************************
  * @attention
  *
  * <h2><center>© COPYRIGHT 2013 STMicroelectronics</center></h2>
  *
  * Licensed under MCD-ST Liberty SW License Agreement V2, (the "License");
  * You may not use this file except in compliance with the License.
  * You may obtain a copy of the License at:
  *
  *        http://www.st.com/software_license_agreement_liberty_v2
  *
  * Unless required by applicable law or agreed to in writing, software 
  * distributed under the License is distributed on an "AS IS" BASIS, 
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  *
  ******************************************************************************
  */

/* Includes ------------------------------------------------------------------*/
#include "lwip/debug.h"
#include "lwip/stats.h"
#include "lwip/tcp.h"
#include "main.h"
#include "memp.h"
#include "main.h"
#include <stdio.h>
#include <string.h>

#if LWIP_TCP
/* Private typedef -----------------------------------------------------------*/
/* Private define ------------------------------------------------------------*/
/* Private macro -------------------------------------------------------------*/
/* Private variables ---------------------------------------------------------*/

u8_t  recev_buf[50];
__IO uint32_t message_count=0;

u8_t   data[100];

struct tcp_pcb *echoclient_pcb;


/* ECHO protocol states */
enum echoclient_states
{
  ES_NOT_CONNECTED = 0,
  ES_CONNECTED,
  ES_RECEIVED,
  ES_CLOSING,
};


/* structure to be passed as argument to the tcp callbacks */
struct echoclient
{
  enum echoclient_states state; /* connection status */
  struct tcp_pcb *pcb;          /* pointer on the current tcp_pcb */
  struct pbuf *p_tx;            /* pointer on pbuf to be transmitted */
};


/* Private function prototypes -----------------------------------------------*/
static err_t tcp_echoclient_recv(void *arg, struct tcp_pcb *tpcb, struct pbuf *p, err_t err);
static void tcp_echoclient_connection_close(struct tcp_pcb *tpcb, struct echoclient * es);
static err_t tcp_echoclient_poll(void *arg, struct tcp_pcb *tpcb);
static err_t tcp_echoclient_sent(void *arg, struct tcp_pcb *tpcb, u16_t len);
static void tcp_echoclient_send(struct tcp_pcb *tpcb, struct echoclient * es);
static err_t tcp_echoclient_connected(void *arg, struct tcp_pcb *tpcb, err_t err);

/* Private functions ---------------------------------------------------------*/


/**
* @brief  Connects to the TCP echo server
* @param  None
* @retval None
*/
void tcp_echoclient_connect(void)
{
  struct ip_addr DestIPaddr;
  
  /* create new tcp pcb */
  echoclient_pcb = tcp_new();
  
  if (echoclient_pcb != NULL)
  {
    IP4_ADDR( &DestIPaddr, DEST_IP_ADDR0, DEST_IP_ADDR1, DEST_IP_ADDR2, DEST_IP_ADDR3 );
    
    /* connect to destination address/port */
    tcp_connect(echoclient_pcb,&DestIPaddr,DEST_PORT,tcp_echoclient_connected);
  }
  else
  {
    /* deallocate the pcb */
    memp_free(MEMP_TCP_PCB, echoclient_pcb);
#ifdef SERIAL_DEBUG
    printf("\n\r can not create tcp pcb");
#endif 
  }
}

/**
  * @brief Function called when TCP connection established
  * @param tpcb: pointer on the connection contol block
  * @param err: when connection correctly established err should be ERR_OK 
  * @retval err_t: returned error 
  */
static err_t tcp_echoclient_connected(void *arg, struct tcp_pcb *tpcb, err_t err)
{
  struct echoclient *es = NULL;
  
  if (err == ERR_OK)   
  {
    /* allocate structure es to maintain tcp connection informations */
    es = (struct echoclient *)mem_malloc(sizeof(struct echoclient));
  
    if (es != NULL)
    {
      es->state = ES_CONNECTED;
      es->pcb = tpcb;
      
      sprintf((char*)data, "sending tcp client message %d", message_count);
        
      /* allocate pbuf */
      es->p_tx = pbuf_alloc(PBUF_TRANSPORT, strlen((char*)data) , PBUF_POOL);
         
      if (es->p_tx)
      {       
        /* copy data to pbuf */
        pbuf_take(es->p_tx, (char*)data, strlen((char*)data));
        
        /* pass newly allocated es structure as argument to tpcb */
        tcp_arg(tpcb, es);
  
        /* initialize LwIP tcp_recv callback function */ 
        tcp_recv(tpcb, tcp_echoclient_recv);
  
        /* initialize LwIP tcp_sent callback function */
        tcp_sent(tpcb, tcp_echoclient_sent);
  
        /* initialize LwIP tcp_poll callback function */
        tcp_poll(tpcb, tcp_echoclient_poll, 1);
    
        /* send data */
        tcp_echoclient_send(tpcb,es);
        
        return ERR_OK;
      }
    }
    else
    {
      /* close connection */
      tcp_echoclient_connection_close(tpcb, es);
      
      /* return memory allocation error */
      return ERR_MEM;  
    }
  }
  else
  {
    /* close connection */
    tcp_echoclient_connection_close(tpcb, es);
  }
  return err;
}