---
title: "STM32 + W5500 DNS porting implementation"
url: "https://maker.wiznet.io/chen/projects/stm32-w5500-dns-porting-implementation/"
markdown_url: "https://maker.wiznet.io/chen/projects/stm32-w5500-dns-porting-implementation/md"
type: "UCC: User Created Content"
author: "夜风~"
author_url: "https://blog.csdn.net/u014470361/article/details/79240054?ops_request_misc=&request_id=&biz_id=102&utm_term=arduino%20stm32%20w5500&utm_medium=distribute.pc_search_result.none-task-blog-2~blog~sobaiduweb~default-2-79240054.nonecase&spm=1018.2226.3001.4450"
editor: "WIZnet"
editor_url: "https://maker.wiznet.io/"
original_author: "夜风~"
original_url: "https://blog.csdn.net/u014470361/article/details/79240054?ops_request_misc=&request_id=&biz_id=102&utm_term=arduino%20stm32%20w5500&utm_medium=distribute.pc_search_result.none-task-blog-2~blog~sobaiduweb~default-2-79240054.nonecase&spm=1018.2226.3001.4450"
license: "Apache License 2.0 (Apache-2.0)"
published: "2022-11-01"
language: "en"
tags: ["W5500"]
hardware: ["M5Stack LAN Module with W5500"]
likes: 4
views: 1524
comments: 0
source: "WIZnet Makers (https://maker.wiznet.io/)"
---

# STM32 + W5500 DNS porting implementation

> This article introduce how to port DNS of W5500 to STM32 MCU

Original author: 夜风~ (source: https://blog.csdn.net/u014470361/article/details/79240054?ops_request_misc=&request_id=&biz_id=102&utm_term=arduino%20stm32%20w5500&utm_medium=distribute.pc_search_result.none-task-blog-2~blog~sobaiduweb~default-2-79240054.nonecase&spm=1018.2226.3001.4450)

## Components

- **M5Stack LAN Module with W5500** x 1 ([docs](https://docs.m5stack.com/en/base/lan_base))

## Article

什么是DNS?
DNS: Domain Name System，域名系统。简单理解，我们平时在浏览器上输入的都是域名，如www.baidu.com，这种域名便于人们的记忆和沟通。你可以很轻松的记住10个域名，但要你记住10个纯数字的ip地址，那就比较费劲了，但电脑通讯的时候是通过ip来通讯的。那么DNS就可以解决这个问题，把域名转化为IP地址。具体DNS的详细内容可参考该文章：http://blog.51cto.com/369369/812889

W5500的DNS移植过程
紧接上一篇文章，DNS的移植就比较简单。首先，还是添加驱动文件。

查询dns.h 头文件，有如下定义，DNS服务器的端口号是53，通讯的协议是UDP协议，默认的域名长度是16。

#define MAX_DOMAIN_NAME 16 // for example "www.google.com"
#define IPPORT_DOMAIN 53 ///< DNS server port number
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DNS的配置主要调用了DNS_init和DNS_run函数，下面编写DNS的Test函数，向DNS输入域名，查看DNS是否返回这个域名的IP地址。具体代码如下：

#define SOCKET_DNS 2//定义一个SOCKET口，W5500有8个，0-7都行
wiz_NetInfo gWIZNETINFO = { .mac = {0x78, 0x83, 0x68, 0x88, 0x56, 0x38},
.ip = {192, 168, 4,17},
.sn = {255,255,255,0},
.gw = {192, 168,4,1},
.dns = {180,76,76,76},
.dhcp = NETINFO_DHCP};
uint8_t DNS_2nd[4]={168,126,63,1};//定义一个备用的DNS
uint8_t Domain_name[]="www.baidu.com";//域名
uint8_t Domain_IP[4]={0,};//存放DNS返回的域名对应的IP地址
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void DNS_Test(void)
{
int8_t ret;
//打印出两个DNS
printf("\r\n=== DNS Client Example ===============\r\n");
printf("> DNS 1st : %d.%d.%d.%d\r\n", gWIZNETINFO.dns[0], gWIZNETINFO.dns[1], gWIZNETINFO.dns[2], gWIZNETINFO.dns[3]);
printf("> DNS 2nd : %d.%d.%d.%d\r\n", DNS_2nd[0], DNS_2nd[1], DNS_2nd[2], DNS_2nd[3]);
printf("======================================\r\n");
printf("> Example Domain Name : %s\r\n", Domain_name);

/* DNS client initialization */
DNS_init(SOCKET_DNS, gDATABUF);//初始化
/* DNS procssing */
if ((ret = DNS_run(gWIZNETINFO.dns, Domain_name, Domain_IP)) > 0) // try to 1st DNS，向gWIZNETINFO.dns这个DNS服务器查询Domain_name这个域名的IP地址，返回的IP地址存放到Domain_IP中
{
printf("> 1st DNS Reponsed\r\n");
}
else if ((ret != -1) && ((ret = DNS_run(DNS_2nd, Domain_name, Domain_IP))>0)) // retry to 2nd DNS
{
printf("> 2nd DNS Reponsed\r\n");
}
else if(ret == -1)
{
printf("> MAX_DOMAIN_NAME is too small. Should be redefined it.\r\n");
}
else
{
printf("> DNS Failed\r\n");
}
if(ret > 0)
{
printf("> Translated %s to %d.%d.%d.%d\r\n",Domain_name,Domain_IP[0],Domain_IP[1],Domain_IP[2],Domain_IP[3]);
}
}

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DNS返回值有三个：-1、0和1,如下：

/*
* @brief DNS process
* @details Send DNS query and receive DNS response
* @param dns_ip : DNS server ip
* @param name : Domain name to be queryed
* @param ip_from_dns : IP address from DNS server
* @return -1 : failed. @ref MAX_DOMIN_NAME is too small \n //返回-1，输入的域名太长，定义的域名最大值太小
* 0 : failed (Timeout or Parse error)\n//返回-1，超时了
* 1 : success//成功
* @note This funtion blocks until success or fail. max time = @ref MAX_DNS_RETRY * @ref DNS_WAIT_TIME
*/
int8_t DNS_run(uint8_t * dns_ip, uint8_t * name, uint8_t * ip_from_dns);
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调用DNS_Test()函数，进行DNS测试，向2个DNS查询www.baidu.com的IP地址。

void W5500_ChipInit(void)
{
W5500_RESET();
RegisterFunction();
ChipParametersConfiguration();
NetworkParameterConfiguration();
DHCP_SET();
DNS_Test();//DNS测试
}
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下载程序执行，串口的输出如下图：

可以看到向DNS查询域名www.baidu.com的ip时，第一个DNS响应了，得到域名对应的IP是：61.135.169.125。在浏览器中输入该地址，成功打开了百度，DNS解析成功。

移植的源程序见链接：https://download.csdn.net/download/u014470361/10234803
————————————————
版权声明：本文为CSDN博主「夜风~」的原创文章，遵循CC 4.0 BY-SA版权协议，转载请附上原文出处链接及本声明。
原文链接：https://blog.csdn.net/u014470361/article/details/79240054

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Source: https://maker.wiznet.io/chen/projects/stm32-w5500-dns-porting-implementation/