LwIP1.4.1连接经常会断开无法连接上但可以ping通这是什么原因？

描述：改自realtouch的代码，用作服务器端，使用tcpip通信，上位机连接一段时间后，会自动断开，无法收发数据，上位机报错the network connection was closed by the peer，下位机报错-12或者-13，此时可以ping通。这是什么原因？
服务器端代码如下：

static void tcpserv_thread_entry(void* parameter)
{
char *recv_data_buf,*send_data_buf; //
rt_uint32_t sin_size;
int sock, connected;
struct sockaddr_in server_addr, client_addr;
rt_uint16_t received_len,send_len;
recv_data_buf = (char *)rt_malloc(RECV_BUF_SIZE); //
send_data_buf = (char *)rt_malloc(SEND_BUF_SIZE);
if (NULL == recv_data_buf || NULL == send_data_buf)
{
rt_kprintf("No memory
");
goto TCP_SERVER_QUIT;
}
rt_memset(recv_data_buf,0x0,RECV_BUF_SIZE);
rt_memset(send_data_buf,0x0,SEND_BUF_SIZE);
//
if ((sock = socket(AF_INET, SOCK_STREAM, 0)) == -1)
{
//
rt_kprintf("Socket error
");
goto TCP_SERVER_QUIT;
}
//
server_addr.sin_family = AF_INET;
server_addr.sin_port = htons(SERVER_PORT); //
server_addr.sin_addr.s_addr = INADDR_ANY;
rt_memset(&(server_addr.sin_zero),8, sizeof(server_addr.sin_zero));
//
if (bind(sock, (struct sockaddr *)&server_addr, sizeof(struct sockaddr)) == -1)
{
//
rt_kprintf("Unable to bind
");
goto TCP_SERVER_QUIT;
}
//
if (listen(sock, 5) == -1)
{
rt_kprintf("Listen error
");
goto TCP_SERVER_QUIT;
}
rt_kprintf("TCPServer Waiting for client on port %d...
",SERVER_PORT);
sin_size = sizeof(struct sockaddr_in);
while(1)
{
//
connected = accept(sock, (struct sockaddr )&client_addr, &sin_size);
//
received_len = recv(connected,recv_data_buf, RECV_BUF_SIZE, 0);
if (received_len > 0)
{
//ATE_LinkComing(ATE_LINK_ETH);
//recv_data_buf[received_len] = '';
TCP_data_process(recv_data_buf,received_len,send_data_buf,&send_len);
//rt_uint16_t temp = SHORT_little_endian_TO_big_endian(send_len);
send(connected, &send_len, sizeof(send_len), 0); //
send(connected, send_data_buf, send_len, 0);//
//rt_memset(send_data_buf,0x0,send_len);
}
/ 关闭这个connected socket */
lwip_close(connected);
}
TCP_SERVER_QUIT:
rt_kprintf("error,TCP Server quit
");
//
lwip_close(sock);
//
rt_free(recv_data_buf);
rt_free(send_data_buf);
RT_ASSERT(0);
return ;
}
无法连接后，lwip的log就停住了
lwip_accept(0)…
lwip_accept(0) returning new sock=1 addr=192.168.1.20 port=48014
lwip_recvfrom(1, 20011170, 2048, 0x0, ..)
lwip_recvfrom: top while sock->lastdata=00000000
lwip_recvfrom: netconn_recv err=0, netbuf=200178b0
lwip_recvfrom: buflen=8 len=2048 off=0 sock->lastoffset=0
lwip_recvfrom(1): addr=192.168.1.20 port=48014 len=8
lwip_recvfrom: deleting netbuf=200178b0
lwip_send(1, data=2000e290, size=2, flags=0x0)
lwip_send(1) err=0 written=2
lwip_send(1, data=2001197c, size=8, flags=0x0)
lwip_send(1) err=0 written=8
lwip_close(1)
lwip_accept(0)…
lwip_accept(0) returning new sock=1 addr=192.168.1.20 port=48015
lwip_recvfrom(1, 20011170, 2048, 0x0, ..)
lwip_recvfrom: top while sock->lastdata=00000000
lwip_recvfrom: netconn_recv err=0, netbuf=200178b0
lwip_recvfrom: buflen=8 len=2048 off=0 sock->lastoffset=0
lwip_recvfrom(1): addr=192.168.1.20 port=48015 len=8
lwip_recvfrom: deleting netbuf=200178b0
lwip_send(1, data=2000e290, size=2, flags=0x0)
lwip_send(1) err=0 written=2
lwip_send(1, data=2001197c, size=8, flags=0x0)
lwip_send(1) err=0 written=8
lwip_close(1)
lwip_accept(0)…
lwip_accept(0) returning new sock=1 addr=192.168.1.20 port=47757
lwip_recvfrom(1, 20011170, 2048, 0x0, ..)
lwip_recvfrom: top while sock->lastdata=00000000
lwip_recvfrom: netconn_recv err=-12, netbuf=00000000
lwip_recvfrom(1): buf == NULL, error is “Connection closed.”!
lwip_close(1)
lwip_accept(0)…
lwip_accept(0) returning new sock=1 addr=192.168.1.20 port=47758
lwip_recvfrom(1, 20011170, 2048, 0x0, ..)
lwip_recvfrom: top while sock->lastdata=00000000
lwip_recvfrom: netconn_recv err=-12, netbuf=00000000
lwip_recvfrom(1): buf == NULL, error is “Connection closed.”!
lwip_close(1)
lwip_accept(0)…
lwip_accept(0) returning new sock=1 addr=192.168.1.20 port=47759
lwip_recvfrom(1, 20011170, 2048, 0x0, ..)
lwip_recvfrom: top while sock->lastdata=00000000
lwip_recvfrom: netconn_recv err=-12, netbuf=00000000
lwip_recvfrom(1): buf == NULL, error is “Connection closed.”!
lwip_close(1)
lwip_accept(0)…
lwip_accept(0) returning new sock=1 addr=192.168.1.20 port=48017
lwip_recvfrom(1, 20011170, 2048, 0x0, ..)
lwip_recvfrom: top while sock->lastdata=00000000
lwip_recvfrom: netconn_recv err=0, netbuf=200178b0
lwip_recvfrom: buflen=8 len=2048 off=0 sock->lastoffset=0
lwip_recvfrom(1): addr=192.168.1.20 port=48017 len=8
lwip_recvfrom: deleting netbuf=200178b0
lwip_send(1, data=2000e290, size=2, flags=0x0)
lwip_send(1) err=0 written=2
lwip_send(1, data=2001197c, size=8, flags=0x0)
lwip_send(1) err=0 written=8
lwip_close(1)
lwip_accept(0)…
lwip_accept(0) returning new sock=1 addr=192.168.1.20 port=47760
lwip_recvfrom(1, 20011170, 2048, 0x0, ..)
lwip_recvfrom: top while sock->lastdata=00000000

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此时，ping是正常的