STM32F107+LWIP怎样判断网络已经连接成功或断开的？

我现在在使用STM32F107+LWIP+DP83848进行tcp通讯，如何判断网络已经连接成功或断开的?怎么样能够使STM32F107随时接入以太网都可以通讯，我的程序如下，求指点
void LwIP_Init(void)
{
struct ip_addr ipaddr;        //IP地址
struct ip_addr netmask;        //子掩码
struct ip_addr gw; //网关地址
uint8_t macaddress[6]={0,0,0,0,0,1}; //以太网控制器物理地址，即MAC地址
/* Initializes the dynamic memory heap defined by MEM_SIZE.*/
mem_init();
/* Initializes the memory pools defined by MEMP_NUM_x.*/
memp_init();
#if LWIP_DHCP
ipaddr.addr = 0;
netmask.addr = 0;
gw.addr = 0;
#else
IP4_ADDR(&ipaddr, 192, 168, 1, 200);
IP4_ADDR(&netmask, 255, 255, 255, 0);
IP4_ADDR(&gw, 192, 168, 1, 1);
#endif
Set_MAC_Address(macaddress);
/* - netif_add(struct netif *netif, struct ip_addr *ipaddr,
struct ip_addr *netmask, struct ip_addr *gw,
void *state, err_t (* init)(struct netif *netif),
err_t (* input)(struct pbuf *p, struct netif *netif))
Adds your network interface to the netif_list. Allocate a struct
netif and pass a pointer to this structure as the first argument.
Give pointers to cleared ip_addr structures when using DHCP,
or fill them with sane numbers otherwise. The state pointer may be NULL.
The init function pointer must point to a initialization function for
your ethernet netif interface. The following code illustrates it's use.*/
netif_add(&netif, &ipaddr, &netmask, &gw, NULL, eernetif_init, eernet_input);
/* Registers the default network interface.*/
netif_set_default(&netif);
#if LWIP_DHCP
/* Creates a new DHCP client for this interface on the first call.
Note: you must call dhcp_fine_tmr() and dhcp_coarse_tmr() at
the predefined regular intervals after starting the client.
You can peek in the netif->dhcp struct for the actual DHCP status.*/
dhcp_start(&netif);
#endif
/* When the netif is fully configured this function must be called.*/
netif_set_up(&netif);
tcp_client_init();
}
/**
* @brief Called when a frame is received
* @param None
* @retval None
*/
void LwIP_Pkt_Handle(void)
{
/* Read a received packet from the Ethernet buffers and send it to the lwIP for handling */
ethernetif_input(&netif);
}
/**
* @brief LwIP periodic tasks
* @param localtime the current LocalTime value
* @retval None
*/
void LwIP_Periodic_Handle(__IO uint32_t localtime)
{
/* TCP periodic process every 250 ms */
if (localtime - TCPTimer >= TCP_TMR_INTERVAL)
{
TCPTimer = localtime;
tcp_tmr();
}
/* ARP periodic process every 5s */
if (localtime - ARPTimer >= ARP_TMR_INTERVAL)
{
ARPTimer = localtime;
etharp_tmr();
}
#if LWIP_DHCP
/* Fine DHCP periodic process every 500ms */
if (localtime - DHCPfineTimer >= DHCP_FINE_TIMER_MSECS)
{
DHCPfineTimer = localtime;
dhcp_fine_tmr();
}
/* DHCP Coarse periodic process every 60s */
if (localtime - DHCPcoarseTimer >= DHCP_COARSE_TIMER_MSECS)
{
DHCPcoarseTimer = localtime;
dhcp_coarse_tmr();
}
#endif
}
/**
* @brief LCD & LEDs periodic handling
* @param localtime: the current LocalTime value
* @retval None
*/
void Display_Periodic_Handle(__IO uint32_t localtime)
{
/* 250 ms */
if (localtime - DisplayTimer >= LCD_TIMER_MSECS)
{
DisplayTimer = localtime;
#if LWIP_DHCP
/* We have got a new IP address so update the display */
if (IPaddress ！= netif.ip_addr.addr)
{        
/* Read the new IP address */
IPaddress = netif.ip_addr.addr;        
/* Display the new IP address */
if (netif.flags & NETIF_FLAG_DHCP)
{
tcp_client_init();        
}
}
else if (IPaddress == 0)
{
/* If no response from a DHCP server for MAX_DHCP_TRIES times */
/* stop the dhcp client and set a static IP address */
if (netif.dhcp->tries > MAX_DHCP_TRIES)
{
struct ip_addr ipaddr;
struct ip_addr netmask;
struct ip_addr gw;
dhcp_stop(&netif);
IP4_ADDR(&ipaddr, 192, 168, 1, 8);
IP4_ADDR(&netmask, 255, 255, 255, 201);
IP4_ADDR(&gw, 192, 168, 1, 1);
netif_set_addr(&netif, &ipaddr , &netmask, &gw);
}
}
#endif
}
}
void tcp_client_init(void)
{
struct tcp_pcb *tpcb;
struct ip_addr ipaddr;
IP4_ADDR(&ipaddr, 192, 168, 1, 125);         //远程主机
/* Create a new TCP control block */
tpcb = tcp_new();
/* Assign to the new pcb a local IP address and a port number */
tcp_bind(tpcb, IP_ADDR_ANY, TCP_PORT);
/* Connect to the server: send the SYN */
tcp_connect(tpcb, &ipaddr, TCP_PORT, tcp_client_accept);
}
/**
* @brief This funtion is called when a TCP connection has been established on the port TCP_PORT.
* @param arg        user supplied argument
* @param pcb        the tcp_pcb which accepted the connection
* @param err error value
* @retval ERR_OK
*/
err_t tcp_client_accept(void *arg, struct tcp_pcb *tpcb, err_t err)
{
/* Specify the function that should be called when the TCP connection receives data */
tcp_recv(tpcb, tcp_client_recv);
return ERR_OK;
}
/**
* @brief This function is called when a data is received over the TCP_PORT.
* The received data contains the number of the led to be toggled.
* @param arg        user supplied argument
* @param pcb        the tcp_pcb which accepted the connection
* @param p the packet buffer that was received
* @param err error value
* @retval ERR_OK
*/
static err_t tcp_client_recv(void *arg, struct tcp_pcb *tpcb, struct pbuf *p, err_t err)
{
uint8_t Data_len;
/* Inform TCP that we have taken the data. */
tcp_recved(tpcb, p->tot_len);
Data_len = p->len;
memcpy(RX, p->payload, Data_len);
tcp_write(tpcb,&LocalDisplay,sizeof(LocalDisplay),1);        
/* Free the p buffer */
pbuf_free(p);
return ERR_OK;
}

小编可以试试这样的解决过程：
1.检查TCP是否断开：if(pcb->state==CLOSED){}
2.关闭之前的pcb：tcp_abort(client_pcb)；
3.重新连接TCP：tcp_client_connect()；

同意楼上，有一些标志位，可以判断是否断网，连接上网络等

同样问题，小编解决没呢，能分享一下吗

同样问题，小编解决没呢，能分享一下吗