是在运行时出错的。
PING是官方例程contrib-1.4.1：
/**
* @file
* Ping sender module
*
*/

/*
* Redistribution and use in source and binary forms, with or without modification,
* are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice,
*    this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright notice,
*    this list of conditions and the following disclaimer in the documentation
*    and/or other materials provided with the distribution.
* 3. The name of the author may not be used to endorse or promote products
*    derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
* SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
* OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
* IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
* OF SUCH DAMAGE.
*
* This file is part of the lwIP TCP/IP stack.
*
*/

/**
* This is an example of a "ping" sender (with raw API and socket API).
* It can be used as a start point to maintain opened a network connection, or
* like a network "watchdog" for your device.
*
*/

#include "lwip/opt.h"

#if LWIP_RAW /* don't build if not configured for use in lwipopts.h */

#include "ping.h"

#include "lwip/mem.h"
#include "lwip/raw.h"
#include "lwip/icmp.h"
#include "lwip/netif.h"
#include "lwip/lwip_sys.h"
#include "lwip/timers.h"
#include "lwip/inet_chksum.h"

#if PING_USE_SOCKETS
#include "lwip/sockets.h"
#include "lwip/inet.h"
#endif /* PING_USE_SOCKETS */


/**
* PING_DEBUG: Enable debugging for PING.
*/
#ifndef PING_DEBUG
#define PING_DEBUG     LWIP_DBG_ON
#endif

/** ping target - should be a "ip_addr_t" */
#ifndef PING_TARGET
#define PING_TARGET   (netif_default?netif_default->gw:ip_addr_any)
#endif

/** ping receive timeout - in milliseconds */
#ifndef PING_RCV_TIMEO
#define PING_RCV_TIMEO 1000
#endif

/** ping delay - in milliseconds */
#ifndef PING_DELAY
#define PING_DELAY     20000
#endif

/** ping identifier - must fit on a u16_t */
#ifndef PING_ID
#define PING_ID        0xAFAF
#endif

/** ping additional data size to include in the packet */
#ifndef PING_DATA_SIZE
#define PING_DATA_SIZE 32
#endif

/** ping result action - no default action */
#ifndef PING_RESULT
#define PING_RESULT(ping_ok)
#endif

/* ping variables */
static u16_t ping_seq_num;
static u32_t ping_time;
//OS_STK ping_thread_STK[512];       

#if !PING_USE_SOCKETS
static struct raw_pcb *ping_pcb;
#endif /* PING_USE_SOCKETS */

/** Prepare a echo ICMP request */
static void
ping_prepare_echo( struct icmp_echo_hdr *iecho, u16_t len)
{
  size_t i;
  size_t data_len = len - sizeof(struct icmp_echo_hdr);

  ICMPH_TYPE_SET(iecho, ICMP_ECHO);
  ICMPH_CODE_SET(iecho, 0);
  iecho->chksum = 0;
  iecho->id     = PING_ID;
  iecho->seqno  = htons(++ping_seq_num);

  /* fill the additional data buffer with some data */
  for(i = 0; i < data_len; i++) {
    ((char*)iecho)[sizeof(struct icmp_echo_hdr) + i] = (char)i;
  }

  iecho->chksum = inet_chksum(iecho, len);
}

#if PING_USE_SOCKETS

/* Ping using the socket ip */
static err_t
ping_send(int s, ip_addr_t *addr)
{
  int err;
  struct icmp_echo_hdr *iecho;
  struct sockaddr_in to;
  size_t ping_size = sizeof(struct icmp_echo_hdr) + PING_DATA_SIZE;
  LWIP_ASSERT("ping_size is too big", ping_size <= 0xffff);

  iecho = (struct icmp_echo_hdr *)mem_malloc((mem_size_t)ping_size);
  if (!iecho) {
    return ERR_MEM;
  }

  ping_prepare_echo(iecho, (u16_t)ping_size);

  to.sin_len = sizeof(to);
  to.sin_family = AF_INET;
  inet_addr_from_ipaddr(&to.sin_addr, addr);

  err = lwip_sendto(s, iecho, ping_size, 0, (struct sockaddr*)&to, sizeof(to));

  mem_free(iecho);

  return (err ? ERR_OK : ERR_VAL);
}

static void
ping_recv(int s)
{
  char buf[64];
  int fromlen, len;
  struct sockaddr_in from;
  struct ip_hdr *iphdr;
  struct icmp_echo_hdr *iecho;


        while((len = lwip_recvfrom(s, buf, sizeof(buf), 0, (struct sockaddr*)&from, (socklen_t*)&fromlen)) > 0) {
    if (len >= (int)(sizeof(struct ip_hdr)+sizeof(struct icmp_echo_hdr))) {
      ip_addr_t fromaddr;
      inet_addr_to_ipaddr(&fromaddr, &from.sin_addr);
      LWIP_DEBUGF( PING_DEBUG, ("ping: recv "));
                printf("ping: recv");
      ip_addr_debug_print(PING_DEBUG, &fromaddr);
      LWIP_DEBUGF( PING_DEBUG, (" %"U32_F" ms ", (sys_now() - ping_time)));

      iphdr = (struct ip_hdr *)buf;
      iecho = (struct icmp_echo_hdr *)(buf + (IPH_HL(iphdr) * 4));
      if ((iecho->id == PING_ID) && (iecho->seqno == htons(ping_seq_num))) {
        /* do some ping result processing */
        PING_RESULT((ICMPH_TYPE(iecho) == ICMP_ER));
        return;
      } else {
        LWIP_DEBUGF( PING_DEBUG, ("ping: drop "));
      }
    }
  }

  if (len == 0) {
    LWIP_DEBUGF( PING_DEBUG, ("ping: recv - %"U32_F" ms - timeout ", (sys_now()-ping_time)));
  }

  /* do some ping result processing */
  PING_RESULT(0);
}

static void
ping_thread(void *arg)
{
  int s;
  int timeout = PING_RCV_TIMEO;
  ip_addr_t ping_target;

  LWIP_UNUSED_ARG(arg);

  if ((s = lwip_socket(AF_INET, SOCK_RAW, IP_PROTO_ICMP)) < 0) {
    return;
  }

  lwip_setsockopt(s, SOL_SOCKET, SO_RCVTIMEO, &timeout, sizeof(timeout));

  while (1) {

          //printf("ping........... ");
          ping_target = PING_TARGET;
         ping_target .addr=0XFE01A8C0;//192.168.1.254

    if (ping_send(s, &ping_target) == ERR_OK) {
      LWIP_DEBUGF( PING_DEBUG, ("ping: send "));
                printf("ping: send ");
      ip_addr_debug_print(PING_DEBUG, &ping_target);
      LWIP_DEBUGF( PING_DEBUG, (" "));

      ping_time = sys_now();
      ping_recv(s);
    } else {
      LWIP_DEBUGF( PING_DEBUG, ("ping: send "));
      ip_addr_debug_print(PING_DEBUG, &ping_target);
      LWIP_DEBUGF( PING_DEBUG, (" - error "));
    }
    sys_msleep(PING_DELAY);
  }
}

#else /* PING_USE_SOCKETS */

/* Ping using the raw ip */
static u8_t
ping_recv(void *arg, struct raw_pcb *pcb, struct pbuf *p, ip_addr_t *addr)
{
  struct icmp_echo_hdr *iecho;
  LWIP_UNUSED_ARG(arg);
  LWIP_UNUSED_ARG(pcb);
  LWIP_UNUSED_ARG(addr);
  LWIP_ASSERT("p != NULL", p != NULL);

  if ((p->tot_len >= (PBUF_IP_HLEN + sizeof(struct icmp_echo_hdr))) &&
      pbuf_header( p, -PBUF_IP_HLEN) == 0) {
    iecho = (struct icmp_echo_hdr *)p->payload;

    if ((iecho->id == PING_ID) && (iecho->seqno == htons(ping_seq_num))) {
      LWIP_DEBUGF( PING_DEBUG, ("ping: recv "));
      ip_addr_debug_print(PING_DEBUG, addr);
      LWIP_DEBUGF( PING_DEBUG, (" %"U32_F" ms ", (sys_now()-ping_time)));

      /* do some ping result processing */
      PING_RESULT(1);
      pbuf_free(p);
      return 1; /* eat the packet */
    }
  }

  return 0; /* don't eat the packet */
}

static void
ping_send(struct raw_pcb *raw, ip_addr_t *addr)
{
  struct pbuf *p;
  struct icmp_echo_hdr *iecho;
  size_t ping_size = sizeof(struct icmp_echo_hdr) + PING_DATA_SIZE;

  LWIP_DEBUGF( PING_DEBUG, ("ping: send "));
  ip_addr_debug_print(PING_DEBUG, addr);
  LWIP_DEBUGF( PING_DEBUG, (" "));
  LWIP_ASSERT("ping_size <= 0xffff", ping_size <= 0xffff);

  p = pbuf_alloc(PBUF_IP, (u16_t)ping_size, PBUF_RAM);
  if (!p) {
    return;
  }
  if ((p->len == p->tot_len) && (p->next == NULL)) {
    iecho = (struct icmp_echo_hdr *)p->payload;

    ping_prepare_echo(iecho, (u16_t)ping_size);

    raw_sendto(raw, p, addr);
    ping_time = sys_now();
  }
  pbuf_free(p);
}

static void
ping_timeout(void *arg)
{
  struct raw_pcb *pcb = (struct raw_pcb*)arg;
  ip_addr_t ping_target = PING_TARGET;

  LWIP_ASSERT("ping_timeout: no pcb given!", pcb != NULL);

  ping_send(pcb, &ping_target);

  sys_timeout(PING_DELAY, ping_timeout, pcb);
}

static void
ping_raw_init(void)
{
  ping_pcb = raw_new(IP_PROTO_ICMP);
  LWIP_ASSERT("ping_pcb != NULL", ping_pcb != NULL);

  raw_recv(ping_pcb, ping_recv, NULL);
  raw_bind(ping_pcb, IP_ADDR_ANY);
  sys_timeout(PING_DELAY, ping_timeout, ping_pcb);
}

void
ping_send_now()
{
  ip_addr_t ping_target = PING_TARGET;
  LWIP_ASSERT("ping_pcb != NULL", ping_pcb != NULL);
  ping_send(ping_pcb, &ping_target);
}

#endif /* PING_USE_SOCKETS */

void
ping_init(void)
{
#if PING_USE_SOCKETS
        //sys_thread_new("ping_thread", ping_thread, NULL, DEFAULT_THREAD_STACKSIZE, DEFAULT_THREAD_PRIO);
        sys_thread_new("ping_thread", ping_thread, NULL, DEFAULT_THREAD_STACKSIZE, 10);
        //OSTaskCreate(ping_thread,(void *)0,(OS_STK*)&ping_thread_STK[512-1],40);
#else /* PING_USE_SOCKETS */
  ping_raw_init();
#endif /* PING_USE_SOCKETS */
}

#endif /* LWIP_RAW */



发送PING后运行到api_lib.cr的函数netconn_recv（）的  LWIP_ERROR("netconn_accept: invalid recvmbox", sys_mbox_valid(&conn->recvmbox), return ERR_CONN;)测试邮箱是否有效时出错：
//检查一个消息邮箱是否有效
//*mbox:消息邮箱
//返回值:1,有效.
//      0,无效
int sys_mbox_valid(sys_mbox_t *mbox)
{  
        sys_mbox_t m_box=*mbox;
        u8_t ucErr;
        int ret;
        OS_Q_DATA q_data;
        memset(&q_data,0,sizeof(OS_Q_DATA));
        //mymemset(&q_data,0,sizeof(OS_Q_DATA));                 //清除mbox的内存
        ucErr=OSQQuery (m_box->pQ,&q_data);//查询消息队列
        ret=(ucErr<2&&(q_data.OSNMsgs<q_data.OSQSize))?1:0;
//        printf("OSQSize:%d ", q_data.OSQSize);
        if (ret==0)
        {
                printf("邮箱无效. ");
                printf("消息邮箱的大小:%d ", q_data.OSNMsgs);
                printf("查询消息队列:%d ", ucErr);
        }
        //return 1;
        return ret;
}

此时可看到q_data.OSQSize的值为0，正常应该是设定值500.
使用chargen例程时也出现了同样的问题。第一次进入chargen线程出现，然后在客户端连上后再断开时出现邮箱无效。