[参考译文] TM4C129ENCPDT：如何在不打开新连接的情况下通过以太网从客户端向服务器发送数据/(同一套接字)

您好！

 如果在此应用手册  https://www.ti.com/lit/pdf/spna248?中运行客户端示例、您是否会看到相同的连接问题

 我不确定您的代码来自哪里。 它与 STMicroelectronics 示例非常相似。 如果是这种情况、请阅读他们的许可协议  

/**
  ******************************************************************************
  * @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:
  *
  *        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;
}