总的程序代码：https://blog.csdn.net/zlk1214/article/details/80941657
第一步：在工程的所在文件夹创建一个lwip-2.0.3文件夹。然后在lwip的官方网站下载lwip-2.0.3.zip，打开压缩包中的lwip-2.0.3/src文件夹，解压以下文件到工程的lwip-2.0.3目录下：
（1）必须的文件
core/*.c
core/ipv4/*.c
include/*
netif/ethernet.c
netif/ethernetif.c
（2）可选例程
apps/httpd/* （HTTP服务器例程）
apps/netbiosns/* （计算机名解析服务）
（3）WiFi无线网络WPA/WPA2认证用到的算法实现
netif/ppp/polarssl/arc4.c
netif/ppp/polarssl/md5.c
netif/ppp/polarssl/sha1.c
注意：这三个文件中必须将里面的#if条件编译中的PPP_SUPPORT条件去掉，例如：
#if /*PPP_SUPPORT && */LWIP_INCLUDED_POLARSSL_ARC4 // 注释掉前面的宏第二步：解压后，将里面的c文件都添加到工程的lwip-2.0.3分组下。（apps/httpd文件夹下只添加fs.c和httpd.c）
具体添加的文件请看下图：
第三步：创建lwip-2.0.3/include/arch/cc.h文件（平台有关的宏定义），内容如下：
#define PACK_STRUCT_BEGIN __packed // struct前的__packed这个关键字主要用在结构体的定义上：typedef __packed struct。加了这个关键字之后，产生的结构体大小就严格等于结构体内各成员的大小之和，不会添加额外的填充字段。
第四步：创建lwip-2.0.3/include/lwipopts.h文件（lwip协议栈选项），内容如下：
#define NO_SYS 1 // 无操作系统
#define LWIP_NETCONN 0
#define LWIP_SOCKET 0
#define LWIP_STATS 0
#define MEM_ALIGNMENT 4 // STM32单片机是32位的单片机, 因此是4字节对齐的
#define SYS_LIGHTWEIGHT_PROT 0 // 不进行临界区保护
// 配置DHCP
#define LWIP_DHCP 1
#define LWIP_NETIF_HOSTNAME 1
// 配置DNS
#define LWIP_DNS 1
#define LWIP_RAND() ((u32_t)rand())
// WPA/WPA2认证需要用到lwip中的arc4, md5和sha1函数
// 需要修改各文件的第42行, 注释掉条件编译宏
#define LWIP_INCLUDED_POLARSSL_ARC4 1
#define LWIP_INCLUDED_POLARSSL_MD5 1
#define LWIP_INCLUDED_POLARSSL_SHA1 1第五步：编写数据链路层上数据包的收发函数。打开lwip-2.0.3/netif/ethernetif.c文件，按下面的中文注释提示修改代码：
/**
* @file
* Ethernet Interface Skeleton
*
*/
/*
* Copyright (c) 2001-2004 Swedish Institute of Computer Science.
* All rights reserved.
*
* 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.
*
* Author: Adam Dunkels <[email protected]>
*
*/
/*
* This file is a skeleton for developing Ethernet network interface
* drivers for lwIP. Add code to the low_level functions and do a
* search-and-replace for the word "ethernetif" to replace it with
* something that better describes your network interface.
*/
#include "lwip/opt.h"
//#if 0 /* don't build, this is only a skeleton, see previous comment */
#if 1 // 允许编译
#include "lwip/def.h"
#include "lwip/mem.h"
#include "lwip/pbuf.h"
#include "lwip/stats.h"
#include "lwip/snmp.h"
#include "lwip/ethip6.h"
#include "lwip/etharp.h"
#include "netif/ppp/pppoe.h"
// 包含头文件
#include "../../common.h"
#include "../../WiFi.h"
/* Define those to better describe your network interface. */
#define IFNAME0 'e'
#define IFNAME1 'n'
/**
* Helper struct to hold private data used to operate your ethernet interface.
* Keeping the ethernet address of the MAC in this struct is not necessary
* as it is already kept in the struct netif.
* But this is only an example, anyway...
*/
struct ethernetif {
struct eth_addr *ethaddr;
/* Add whatever per-interface state that is needed here. */
};
/* Forward declarations. */
/*static */void ethernetif_input(struct netif *netif); // 必须去掉static
/**
* In this function, the hardware should be initialized.
* Called from ethernetif_init().
*
* @param netif the already initialized lwip network interface structure
* for this ethernetif
*/
static void
low_level_init(struct netif *netif)
{
//struct ethernetif *ethernetif = netif->state; // 无用的变量
/* set MAC hardware address length */
netif->hwaddr_len = ETHARP_HWADDR_LEN;
/* set MAC hardware address */
//netif->hwaddr[0] = ;
//...
//netif->hwaddr[5] = ;
// MAC地址已设置, 注释掉这段代码
/* maximum transfer unit */
netif->mtu = 1500;
/* device capabilities */
/* don't set NETIF_FLAG_ETHARP if this device is not an ethernet one */
netif->flags = NETIF_FLAG_BROADCAST | NETIF_FLAG_ETHARP | NETIF_FLAG_LINK_UP;
#if LWIP_IPV6 && LWIP_IPV6_MLD
/*
* For hardware/netifs that implement MAC filtering.
* All-nodes link-local is handled by default, so we must let the hardware know
* to allow multicast packets in.
* Should set mld_mac_filter previously. */
if (netif->mld_mac_filter != NULL) {
ip6_addr_t ip6_allnodes_ll;
ip6_addr_set_allnodes_linklocal(&ip6_allnodes_ll);
netif->mld_mac_filter(netif, &ip6_allnodes_ll, NETIF_ADD_MAC_FILTER);
}
#endif /* LWIP_IPV6 && LWIP_IPV6_MLD */
/* Do whatever else is needed to initialize interface. */
}
/**
* This function should do the actual transmission of the packet. The packet is
* contained in the pbuf that is passed to the function. This pbuf
* might be chained.
*
* @param netif the lwip network interface structure for this ethernetif
* @param p the MAC packet to send (e.g. IP packet including MAC addresses and type)
* @return ERR_OK if the packet could be sent
* an err_t value if the packet couldn't be sent
*
* @note Returning ERR_MEM here if a DMA queue of your MAC is full can lead to
* strange results. You might consider waiting for space in the DMA queue
* to become available since the stack doesn't retry to send a packet
* dropped because of memory failure (except for the TCP timers).
*/
static err_t
low_level_output(struct netif *netif, struct pbuf *p)
{
//struct ethernetif *ethernetif = netif->state; // 无用的变量
//struct pbuf *q;
uint8_t *buffer; // 添加此变量
//initiate transfer();
#if ETH_PAD_SIZE
pbuf_header(p, -ETH_PAD_SIZE); /* drop the padding word */
#endif
//for (q = p; q != NULL; q = q->next) {
/* Send the data from the pbuf to the interface, one pbuf at a
time. The size of the data in each pbuf is kept in the ->len
variable. */
//send data from(q->payload, q->len);
//}
buffer = WiFi_GetPacketBuffer(); // 获取发送缓冲区 (需要等待之前的帧发送完毕)
pbuf_copy_partial(p, buffer, p->tot_len, 0); // 复制要发送的数据帧到发送缓冲区中
#ifdef WIFI_DISPLAY_PACKET_SIZE
printf("[Send] len=%hd\n", p->tot_len);
#endif
#ifdef WIFI_DISPLAY_PACKET_TX
dump_data(buffer, p->tot_len);
#endif
//signal that packet should be sent();
WiFi_SendPacket(buffer, p->tot_len, NULL, NULL, WIFI_DEFAULT_TIMEOUT_DATAACK);
MIB2_STATS_NETIF_ADD(netif, ifoutoctets, p->tot_len);
if (((u8_t*)p->payload)[0] & 1) {
/* broadcast or multicast packet*/
MIB2_STATS_NETIF_INC(netif, ifoutnucastpkts);
} else {
/* unicast packet */
MIB2_STATS_NETIF_INC(netif, ifoutucastpkts);
}
/* increase ifoutdiscards or ifouterrors on error */
#if ETH_PAD_SIZE
pbuf_header(p, ETH_PAD_SIZE); /* reclaim the padding word */
#endif
LINK_STATS_INC(link.xmit);
return ERR_OK;
}
/**
* Should allocate a pbuf and transfer the bytes of the incoming
* packet from the interface into the pbuf.
*
* @param netif the lwip network interface structure for this ethernetif
* @return a pbuf filled with the received packet (including MAC header)
* NULL on memory error
*/
static struct pbuf *
low_level_input(struct netif *netif)
{
//struct ethernetif *ethernetif = netif->state; // 无用的变量
struct pbuf *p/*, *q*/;
u16_t len;
// 添加变量
const WiFi_DataRx *data = WiFi_GetReceivedPacket();
/* Obtain the size of the packet and put it into the "len"
variable. */
len = data->rx_packet_length;
#ifdef WIFI_DISPLAY_PACKET_SIZE
printf("[Recv] len=%hd", len);
#ifdef WIFI_DISPLAY_PACKET_RXRATES
printf(", SNR=%ddB, NF=-%ddBm, priority=%d", (int)data->snr, data->nf, data->priority);
if (data->rx_rate != 0)
{
printf(", rates: ");
WiFi_PrintRates(data->rx_rate);
}
#endif
printf("\n");
#endif
#ifdef WIFI_DISPLAY_PACKET_RX
dump_data(data->payload, len);
#endif
#if ETH_PAD_SIZE
len += ETH_PAD_SIZE; /* allow room for Ethernet padding */
#endif
/* We allocate a pbuf chain of pbufs from the pool. */
p = pbuf_alloc(PBUF_RAW, len, PBUF_POOL);
if (p != NULL) {
#if ETH_PAD_SIZE
pbuf_header(p, -ETH_PAD_SIZE); /* drop the padding word */
#endif
/* We iterate over the pbuf chain until we have read the entire
* packet into the pbuf. */
//for (q = p; q != NULL; q = q->next) {
/* Read enough bytes to fill this pbuf in the chain. The
* available data in the pbuf is given by the q->len
* variable.
* This does not necessarily have to be a memcpy, you can also preallocate
* pbufs for a DMA-enabled MAC and after receiving truncate it to the
* actually received size. In this case, ensure the tot_len member of the
* pbuf is the sum of the chained pbuf len members.
*/
//read data into(q->payload, q->len);
//}
pbuf_take(p, data->payload, len); // 将数据帧内容复制到pbuf中
//acknowledge that packet has been read();
MIB2_STATS_NETIF_ADD(netif, ifinoctets, p->tot_len);
if (((u8_t*)p->payload)[0] & 1) {
/* broadcast or multicast packet*/
MIB2_STATS_NETIF_INC(netif, ifinnucastpkts);
} else {
/* unicast packet*/
MIB2_STATS_NETIF_INC(netif, ifinucastpkts);
}
#if ETH_PAD_SIZE
pbuf_header(p, ETH_PAD_SIZE); /* reclaim the padding word */
#endif
LINK_STATS_INC(link.recv);
} else {
//drop packet(); // 注释掉
LINK_STATS_INC(link.memerr);
LINK_STATS_INC(link.drop);
MIB2_STATS_NETIF_INC(netif, ifindiscards);
}
return p;
}
/**
* This function should be called when a packet is ready to be read
* from the interface. It uses the function low_level_input() that
* should handle the actual reception of bytes from the network
* interface. Then the type of the received packet is determined and
* the appropriate input function is called.
*
* @param netif the lwip network interface structure for this ethernetif
*/
/*static */void // 必须去掉static
ethernetif_input(struct netif *netif)
{
//struct ethernetif *ethernetif; // 无用的变量
//struct eth_hdr *ethhdr;
struct pbuf *p;
//ethernetif = netif->state; // 注释掉
/* move received packet into a new pbuf */
p = low_level_input(netif);
/* if no packet could be read, silently ignore this */
if (p != NULL) {
/* pass all packets to ethernet_input, which decides what packets it supports */
if (netif->input(p, netif) != ERR_OK) {
LWIP_DEBUGF(NETIF_DEBUG, ("ethernetif_input: IP input error\n"));
pbuf_free(p);
p = NULL;
}
}
}
/**
* Should be called at the beginning of the program to set up the
* network interface. It calls the function low_level_init() to do the
* actual setup of the hardware.
*
* This function should be passed as a parameter to netif_add().
*
* @param netif the lwip network interface structure for this ethernetif
* @return ERR_OK if the loopif is initialized
* ERR_MEM if private data couldn't be allocated
* any other err_t on error
*/
err_t
ethernetif_init(struct netif *netif)
{
struct ethernetif *ethernetif;
LWIP_ASSERT("netif != NULL", (netif != NULL));
ethernetif = mem_malloc(sizeof(struct ethernetif));
if (ethernetif == NULL) {
LWIP_DEBUGF(NETIF_DEBUG, ("ethernetif_init: out of memory\n"));
return ERR_MEM;
}
#if LWIP_NETIF_HOSTNAME
/* Initialize interface hostname */
netif->hostname = "STM32F103RE_SDIO"; // 路由器中显示的名称
#endif /* LWIP_NETIF_HOSTNAME */
/*
* Initialize the snmp variables and counters inside the struct netif.
* The last argument should be replaced with your link speed, in units
* of bits per second.
*/
MIB2_INIT_NETIF(netif, snmp_ifType_ethernet_csmacd, LINK_SPEED_OF_YOUR_NETIF_IN_BPS);
netif->state = ethernetif;
netif->name[0] = IFNAME0;
netif->name[1] = IFNAME1;
/* We directly use etharp_output() here to save a function call.
* You can instead declare your own function an call etharp_output()
* from it if you have to do some checks before sending (e.g. if link
* is available...) */
netif->output = etharp_output;
#if LWIP_IPV6
netif->output_ip6 = ethip6_output;
#endif /* LWIP_IPV6 */
netif->linkoutput = low_level_output;
ethernetif->ethaddr = (struct eth_addr *)&(netif->hwaddr[0]);
/* initialize the hardware */
low_level_init(netif);
return ERR_OK;
}
#endif /* 0 */其中，low_level_output函数调用WiFi_SendPacket函数发送数据包，low_level_input函数调用WiFi_GetReceivedPacket接收数据包。ethernetif_init函数里面还有一个netif->hostname成员变量，该变量决定了设备在路由器管理页面中DHCP客户端列表中的显示名称。
第六步：将lwip的头文件夹“lwip-2.0.3\include”添加到项目属性中的Include路径中去：
另外，为了在程序中使用printf函数，Target选项卡下的Use MicroLIB复选框也要勾选上。
第七步：编写供lwip协议栈使用的sys_now函数。该函数返回一个32位的系统时间，单位为毫秒。该函数必须保证：除非定时器溢出，否则后获取的时间必须大于先获取的时间，不然会导致开机后DHCP长时间获取不到IP地址，并且TCP和UDP也不能正常工作。
例程中该函数位于common.c，函数使用STM32单片机的RTC外设提供时间信息，RTC使用的时钟源是LSI。
/* RTC时间转化为毫秒数 (lwip协议栈要求实现的函数) */
// 该函数必须保证: 除非定时器溢出, 否则后获取的时间必须大于先获取的时间
uint32_t sys_now(void)
{
uint32_t sec[2];
uint32_t div, milli;
do
{
time(&sec[0]); // 秒
div = rtc_divider();
time(&sec[1]);
} while (sec[0] != sec[1]);
// CNT是在DIV从P-1跳变到P-2瞬间发生更新的 (P=RTC_PRESCALER)
if (div == RTC_PRESCALER - 1)
milli = div;
else
milli = RTC_PRESCALER - div - 2;
milli = milli * 1000 / RTC_PRESCALER; // 毫秒
return sec[0] * 1000 + milli;
}第八步：在主函数main中初始化lwip协议栈：
lwip_init();
netbiosns_init();
netbiosns_set_name("STM32F103RE"); // 计算机名
httpd_init();第九步：成功获得WiFi模块的MAC地址后，将无线网卡添加到lwip中：
// 获取网卡MAC地址成功后, 就立即将网卡添加到lwip中, 但暂不把网卡设为"已连接"状态
// 只需要在单片机复位的时候获取一次网卡地址就行, 后面重新连接热点则无需调用此函数
static void mac_address_callback(void *arg, void *data, WiFi_Status status)
{
#if !LWIP_DHCP
struct ip4_addr ipaddr, netmask, gw;
#endif
if (status == WIFI_STATUS_OK)
{
WiFi_Scan(scan_callback, NULL); // 发送扫描热点的命令
memcpy(wifi_88w8686.hwaddr, data, 6); // 将获得的MAC地址复制到全局变量中
printf("MAC Addr: %02X:%02X:%02X:%02X:%02X:%02X\n", wifi_88w8686.hwaddr[0], wifi_88w8686.hwaddr[1], wifi_88w8686.hwaddr[2], wifi_88w8686.hwaddr[3], wifi_88w8686.hwaddr[4], wifi_88w8686.hwaddr[5]);
#if LWIP_DHCP
netif_add(&wifi_88w8686, IP_ADDR_ANY, IP_ADDR_ANY, IP_ADDR_ANY, NULL, ethernetif_init, ethernet_input);
#else
IP4_ADDR(&ipaddr, 192, 168, 43, 15); // IP地址
IP4_ADDR(&netmask, 255, 255, 255, 0); // 子网掩码
IP4_ADDR(&gw, 192, 168, 43, 1); // 网关
netif_add(&wifi_88w8686, &ipaddr, &netmask, &gw, NULL, ethernetif_init, ethernet_input); // 添加WiFi模块到lwip中
#if LWIP_DNS
IP4_ADDR(&ipaddr, 8, 8, 8, 8); // 首选DNS服务器
dns_setserver(0, &ipaddr);
IP4_ADDR(&ipaddr, 8, 8, 4, 4); // 备用DNS服务器
dns_setserver(1, &ipaddr);
#endif
#endif
netif_set_default(&wifi_88w8686); // 设为默认网卡
}
else
printf("Cannot get MAC address!\n");
}其中wifi_88w8686是定义在main.c中的全局变量：
static struct netif wifi_88w8686;请注意DHCP启用/未启用时的区别。若启用了DHCP，则IP地址不需要手动填写，由lwip自动从路由器中获取。
另外，如果是在low_level_init函数中自己设定MAC地址，那么需要注意，MAC地址的第一个字节必须是偶数，不能是奇数。因为如果是奇数的话，这个MAC地址是一个广播地址，不是单播地址，发出的数据包可能会被某些路由器拒收。
第十步：当网络连接成功时，调用netif_set_up通知lwip。当网络连接断开时，调用netif_set_down通知lwip。
如果启用了DHCP，则还需要调用dhcp_start和dhcp_stop。
/* 通知lwip网卡的连接状态 */
static void set_netif(struct netif *netif, uint8_t up)
{
if (up)
{
if (!netif_is_up(netif))
{
netif_set_up(netif);
#if LWIP_DHCP
dhcp_start(netif); // 路由器中显示的DHCP客户名称在ethernetif_init函数中设置
#endif
}
}
else
{
netif_set_down(netif);
#if LWIP_DHCP
dhcp_stop(netif);
#endif
}
}/* WiFi认证成功回调函数 */
void WiFi_AuthenticationCompleteHandler(void)
{
printf("Authenticated!\n");
set_netif(&wifi_88w8686, 1); // 在lwip中启用WiFi网卡
}/* WiFi事件回调函数 */
void WiFi_EventHandler(const WiFi_Event *event)
{
printf("[Event %d] size=%d", event->event_id, event->header.length);
if (event->header.length >= sizeof(WiFi_Event) - sizeof(event->mac_addr))
printf(", reason=%d", event->reason_code);
if (event->header.length >= sizeof(WiFi_Event))
printf(", MAC: %02X:%02X:%02X:%02X:%02X:%02X", event->mac_addr[0], event->mac_addr[1], event->mac_addr[2], event->mac_addr[3], event->mac_addr[4], event->mac_addr[5]);
printf("\n");
switch (event->event_id)
{
case 3:
// 收不到信号 (例如和手机热点建立连接后, 把手机拿走), WiFi模块不会自动重连
printf("Beacon Loss/Link Loss\n");
set_netif(&wifi_88w8686, 0);
break;
case 4:
// Ad-Hoc网络中不止1个结点, 且连接数发生了变化
printf("The number of stations in this ad hoc newtork has changed!\n");
set_netif(&wifi_88w8686, 1);
break;
case 8:
// 认证已解除 (例如手机关闭了热点, 或者连接路由器后因认证失败而自动断开连接)
printf("Deauthenticated!\n");
set_netif(&wifi_88w8686, 0);
break;
case 9:
// 解除了关联
printf("Disassociated!\n");
set_netif(&wifi_88w8686, 0);
break;
case 17:
// Ad-Hoc网络中只剩本结点
printf("All other stations have been away from this ad hoc network!\n");
set_netif(&wifi_88w8686, 0);
break;
case 30:
printf("IBSS coalescing process is finished and BSSID has changed!\n");
break;
}
if (event->header.length > sizeof(WiFi_Event))
dump_data(event + 1, event->header.length - sizeof(WiFi_Event));
// 断线自动重连
/*
if (!netif_is_up(&wifi_88w8686))
{
printf("Reconnecting...\n");
associate_example(); // 只需要调用这个函数重新关联热点就行了, 不需要重新获取MAC地址
}
*/
}static void associate_callback(void *arg, void *data, WiFi_Status status)
{
switch (status)
{
case WIFI_STATUS_OK:
printf("Associated!\n");
set_netif(&wifi_88w8686, 1); // 在lwip中启用WiFi网卡
break;
case WIFI_STATUS_NOTFOUND:
printf("SSID not found!\n");
break;
case WIFI_STATUS_FAIL:
printf("Association failed!\n");
break;
case WIFI_STATUS_INPROGRESS:
printf("Waiting for authentication!\n");
break;
default:
printf("Unknown error! status=%d\n", status);
}
}第十一步：当网卡收到新的数据包时，调用ethernetif_input将数据包交给lwip处理。该函数会在内部调用前面提到的low_level_input函数。
/* WiFi模块收到新的数据帧 */
void WiFi_PacketHandler(const WiFi_DataRx *data)
{
ethernetif_input(&wifi_88w8686); // 交给lwip处理
}第十二步：在main函数的主循环while(1)中调用sys_check_timeouts函数，用于完成lwip内部的各种定时处理。
// lwip协议栈定时处理函数
sys_check_timeouts();/* 显示DHCP分配的IP地址 */
#if LWIP_DHCP
static void display_ip(void)
{
static uint8_t ip_displayed = 0;
struct dhcp *dhcp;
if (dhcp_supplied_address(&wifi_88w8686))
{
if (ip_displayed == 0)
{
ip_displayed = 1;
dhcp = netif_dhcp_data(&wifi_88w8686);
printf("DHCP supplied address!\n");
printf("IP address: %s\n", ip4addr_ntoa(&dhcp->offered_ip_addr));
printf("Subnet mask: %s\n", ip4addr_ntoa(&dhcp->offered_sn_mask));
printf("Default gateway: %s\n", ip4addr_ntoa(&dhcp->offered_gw_addr));
#if LWIP_DNS
printf("DNS Server: %s\n", ip4addr_ntoa(dns_getserver(0)));
dns_test();
#endif
}
}
else
ip_displayed = 0;
}
#endif// 显示DHCP获取到的IP地址
#if LWIP_DHCP
display_ip();
#endif