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This article introduces the relevant knowledge points of the DNS module in Node.js in detail, and shares the relevant example code. Interested friends can refer to it.
1. DNS
In Node.js, the DNS module is provided to implement domain name search and domain name resolution processing.
In the DNS module, three main methods and a series of convenient methods are provided.
resolve method: used to resolve a domain name into a set of DNS records.
reverse method: Used to convert an IP address into a set of domain names.
lookup method: Used to convert a domain name into an IP address.
The other convenience methods in the DNS module are a convenient form of the resolve method.
#2. Use the resolve method to resolve the domain name into a DNS record
`DNS.resolve(domain, [rrtype ], callback(err, address){...})`
The domain parameter is a string, used to specify the domain name that needs to be resolved, and can include subdomain names.
The rrtypr parameter is a string used to specify the record type to be obtained. The record types that can be specified are as follows.
A, this parameter value is the default value. When the record type is A, the record maps an IPv4 address to a domain name.
AAAA, when the record type is AAAA, this record maps an IPv6 address to a domain name.
CNAME, when the record type is CNAME, it means that the record is an alias record of a domain name. For example, a www.example.com domain name record may be an example.com domain name record. Alias record.
MX, the MX record points to a mail server in a domain that uses SMTP. For example, when you want to send an email to the person@domain.com email address, the MX of the domain.com domain The record contains the email server address from which the email was sent.
TXT, TXT record is the description record attached to the domain name.
SRV, SRV records are used to provide information for all available services in a specific domain.
PTR, PTR record is used for reverse address resolution. This record maps a domain name to an IPv4 address.
NS, NS (Name Server) records are domain name server records, used to specify which DNS server resolves the domain name.
The callback function has two parameters. err is the error object triggered when domain name resolution fails. The addresses parameter is an array that stores all obtained DNS records.
3. Various convenient methods customized for the resolve method
DNS.resolve4(domain, callback), Get the IPv4 address
DNS.resolve6(domain, callback), get the IPv6 address
DNS.resolveMx(domain, callback), get the MX Records, mail exchange server records
DNS.resolveTxt(domain, callback), obtains TXT records, domain name attached description records
4. Use the lookup method to query the IP address
5. Use the reverse method to reversely resolve an IP address
6. Various error codes in the DNS module
EFORMERR: The DNS server found that the client used malformed query parameters when requesting a query
ESERVFAIL: The DNS server failed to perform the query operation
ENOTFOUND: No domain name found
ENOTIMP: The DNS server cannot perform the query operation requested by the client
EREFUSED: The DNS server refused to perform the query operation
EBADQUERY: Malformed DNS query
EBADNAME: Domain name format is incorrect
EBADFAMILY: Unsupported IP address type
EBADRESP: Malformed DNS reply
ECONNREFUSED: Unable to establish Connection to DNS server
ETIMEOUT: Timeout to establish connection to DNS server
EEOF: Bottom of file reached
EFILE: Failed to read file
ENOMEM: Not enough memory space
EDESTRUCTION: Channel already Destroyed
EBADSTR: String format error
EBADFLAGS: Wrong judgment flag specified
ENONAME: The specified host name is not in numeric format
EBADHINTS: The specified prompt flag is invalid
ENOTINITIALIZED: c-ares class library Initialization has not been completed
ELOADIPHLPAPI: An error was triggered while loading iphlpapi.dll
EADDREGETNETWORKPARAMS: GetNetworkParams function not found
ECANCELLED: DNS query operation was canceled
7. Basic use of DNS module
const dns = require('dns'); let url = 'www.qq.com'; dns.resolve(url, 'A', (err, addresses) => { console.log(addresses); // IPv4地址 [ '103.7.30.123' ] }); dns.resolve(url, 'AAAA', (err, addresses) => { console.log(addresses); // IPv6地址 [ '240e:e1:8100:28::2:16' ] }); dns.resolveMx('qq.com', (err, addresses) => { console.log(addresses); // 邮件交换服务器记录 // [ { exchange: 'mx2.qq.com', priority: 20 }, // { exchange: 'mx1.qq.com', priority: 30 }, // { exchange: 'mx3.qq.com', priority: 10 } ] }); dns.resolveTxt('qq.com', (err, addresses) => { console.log(addresses); // 域名附加的描述记录 // [ [ 'v=spf1 include:spf.mail.qq.com -all' ] ] }); dns.resolveSrv('www.baidu.com', (err, addresses) => { console.log(addresses); // 服务记录 // [] }); dns.resolveNs('www.github.com', (err, addresses) => { console.log(addresses); // 域名服务器记录 // [ 'ns-421.awsdns-52.com', // 'ns-520.awsdns-01.net', // 'ns1.p16.dynect.net', // 'ns2.p16.dynect.net', // 'ns3.p16.dynect.net', // 'ns4.p16.dynect.net', // 'ns-1283.awsdns-32.org', // 'ns-1707.awsdns-21.co.uk' ] }); dns.resolveCname('www.163.com', (err, addresses) => { console.log(addresses); // 获取别名记录 // [ 'www.163.com.lxdns.com' ] }); dns.lookup('google.com', 4, (err, address, family) => { // 查询IP地址 // address,查询到的地址 // family,IPv4或IPv6 console.log(address);// 172.217.27.142 console.log(family);// 4 }); dns.lookup('google.com', 6, (err, address, family) => { console.log(address);// 2404:6800:4008:803::200e console.log(family);// 6 }); dns.reverse('203.188.200.67', (err, domain) => { // 反向解析IP地址 console.log(domain); // [ 'media-router-fp1.prod.media.vip.tp2.yahoo.com' ] });
The above is what I compiled for everyone. I hope it will be helpful to everyone in the future.
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