Node.js v0.10.18 手册 & 文档

DNS#

稳定度: 3 - 稳定

Use require('dns') to access this module. All methods in the dns module use C-Ares except for dns.lookup which uses getaddrinfo(3) in a thread pool. C-Ares is much faster than getaddrinfo but the system resolver is more constant with how other programs operate. When a user does net.connect(80, 'google.com') or http.get({ host: 'google.com' }) the dns.lookup method is used. Users who need to do a large number of lookups quickly should use the methods that go through C-Ares.

使用 require('dns') 引入此模块。dns 模块中的所有方法都使用了 C-Ares，除了 dns.lookup 使用了线程池中的 getaddrinfo(3)。C-Ares 比 getaddrinfo 要快得多，但系统解析器相对于其它程序的操作要更固定。当一个用户使用 net.connect(80, 'google.com') 或 http.get({ host: 'google.com' }) 时会使用 dns.lookup 方法。如果用户需要进行大量的快速查询，则最好使用 C-Ares 提供的方法。

Here is an example which resolves 'www.google.com' then reverse resolves the IP addresses which are returned.

下面是一个解析 'www.google.com' 并反向解析所返回 IP 地址的例子。

      console.log('反向解析 ' + a + ': ' + JSON.stringify(domains));
    });
  });
});

dns.lookup(domain, [family], callback)#

Resolves a domain (e.g. 'google.com') into the first found A (IPv4) or AAAA (IPv6) record. The family can be the integer 4 or 6. Defaults to null that indicates both Ip v4 and v6 address family.

将一个域名（比如 'google.com'）解析为第一个找到的 A 记录（IPv4）或 AAAA 记录（IPv6）。地址族 family 可以是数字 4 或 6，缺省为 null 表示同时允许 IPv4 和 IPv6 地址族。

The callback has arguments (err, address, family). The address argument is a string representation of a IP v4 or v6 address. The family argument is either the integer 4 or 6 and denotes the family of address (not necessarily the value initially passed to lookup).

回调参数为 (err, address, family)。地址 address 参数为一个代表 IPv4 或 IPv6 地址的字符串。地址族 family 参数为数字 4 或 6，地表 address 的地址族（不一定是之前传入 lookup 的值）。

On error, err is an Error object, where err.code is the error code. Keep in mind that err.code will be set to 'ENOENT' not only when the domain does not exist but also when the lookup fails in other ways such as no available file descriptors.

当错误发生时，err 为一个 Error 对象，其中 err.code 为错误代码。请记住 err.code 被设定为 'ENOENT' 的情况不仅是域名不存在，也可能是查询在其它途径出错，比如没有可用文件描述符时。

dns.resolve(domain, [rrtype], callback)#

Resolves a domain (e.g. 'google.com') into an array of the record types specified by rrtype. Valid rrtypes are 'A' (IPV4 addresses, default), 'AAAA' (IPV6 addresses), 'MX' (mail exchange records), 'TXT' (text records), 'SRV' (SRV records), 'PTR' (used for reverse IP lookups), 'NS' (name server records) and 'CNAME' (canonical name records).

将一个域名（比如 'google.com'）解析为一个 rrtype 指定记录类型的数组。有效 rrtypes 取值有 'A'（IPv4 地址，缺省）、'AAAA'（IPv6 地址）、'MX'（邮件交换记录）、'TXT'（文本记录）、'SRV'（SRV 记录）、'PTR'（用于 IP 反向查找）、'NS'（域名服务器记录）和 'CNAME'（别名记录）。

The callback has arguments (err, addresses). The type of each item in addresses is determined by the record type, and described in the documentation for the corresponding lookup methods below.

回调参数为 (err, addresses)。其中 addresses 中每一项的类型取决于记录类型，详见下文对应的查找方法。

On error, err is an Error object, where err.code is one of the error codes listed below.

当出错时，err 参数为一个 Error 对象，其中 err.code 为下文所列出的错误代码之一。

dns.resolve4(domain, callback)#

The same as dns.resolve(), but only for IPv4 queries (A records). addresses is an array of IPv4 addresses (e.g. ['74.125.79.104', '74.125.79.105', '74.125.79.106']).

于 dns.resolve() 一样，但只用于查询 IPv4（A 记录）。addresses 是一个 IPv4 地址的数组（比如 ['74.125.79.104', '74.125.79.105', '74.125.79.106']）。

dns.resolve6(domain, callback)#

The same as dns.resolve4() except for IPv6 queries (an AAAA query).

类似于 dns.resolve4()，但用于 IPv6（AAAA）查询。

dns.resolveMx(domain, callback)#

The same as dns.resolve(), but only for mail exchange queries (MX records).

类似于 dns.resolve()，但用于邮件交换查询（MX 记录）。

addresses is an array of MX records, each with a priority and an exchange attribute (e.g. [{'priority': 10, 'exchange': 'mx.example.com'},...]).

addresses 为一个 MX 记录的数组，每一项包含优先级和交换属性（比如 [{'priority': 10, 'exchange': 'mx.example.com'},...]）。

dns.resolveTxt(domain, callback)#

The same as dns.resolve(), but only for text queries (TXT records). addresses is an array of the text records available for domain (e.g., ['v=spf1 ip4:0.0.0.0 ~all']).

与 dns.resolve() 相似，但用于文本查询（TXT 记录）。addresses 为 domain 可用文本记录的数组（比如 ['v=spf1 ip4:0.0.0.0 ~all']）。

dns.resolveSrv(domain, callback)#

The same as dns.resolve(), but only for service records (SRV records). addresses is an array of the SRV records available for domain. Properties of SRV records are priority, weight, port, and name (e.g., [{'priority': 10, {'weight': 5, 'port': 21223, 'name': 'service.example.com'}, ...]).

查询 SRV 记录，与 dns.resolve() 相似。 addresses 是域名 domain 可用的 SRV 记录数组，每一条记录都包含优先级（priority）、权重（weight）、端口号（port）、服务名称（name）等属性 (比如： [{'priority': 10, {'weight': 5, 'port': 21223, 'name': 'service.example.com'}, ...])。

dns.resolveNs(domain, callback)#

The same as dns.resolve(), but only for name server records (NS records). addresses is an array of the name server records available for domain (e.g., ['ns1.example.com', 'ns2.example.com']).

查询 NS 记录，与 dns.resolve() 相似。 addresses 是域名 domain 可用的 NS 记录数组， (比如： ['ns1.example.com', 'ns2.example.com']).

dns.resolveCname(domain, callback)#

The same as dns.resolve(), but only for canonical name records (CNAME records). addresses is an array of the canonical name records available for domain (e.g., ['bar.example.com']).

查询 CNAME 记录，与 dns.resolve() 相似。 addresses 是域名 domain 可用的 CNAME 记录数组， (比如： ['bar.example.com']).

dns.reverse(ip, callback)#

Reverse resolves an ip address to an array of domain names.

反向解析 IP 地址，返回指向该 IP 地址的域名数组。

The callback has arguments (err, domains).

回调函数接收两个参数： (err, domains).

On error, err is an Error object, where err.code is one of the error codes listed below.

当出错时，err 参数为一个 Error 对象，其中 err.code 为下文所列出的错误代码之一。

dns.getServers()#

Returns an array of IP addresses as strings that are currently being used for resolution

已字符串返回一个当前用于解析的 IP 地址的数组。

dns.setServers(servers)#

Given an array of IP addresses as strings, set them as the servers to use for resolving

指定一个 IP 地址字符串数组，将它们作为解析所用的服务器。

If you specify a port with the address it will be stripped, as the underlying library doesn't support that.

如果您在地址中指定了端口，则端口会被忽略，因为底层库并不支持。

This will throw if you pass invalid input.

如果您传入无效参数，则会抛出异常。

错误代码#

Each DNS query can return one of the following error codes:

每个 DNS 查询都可能返回下列错误代码之一：

dns.NODATA: DNS server returned answer with no data.
dns.FORMERR: DNS server claims query was misformatted.
dns.SERVFAIL: DNS server returned general failure.
dns.NOTFOUND: Domain name not found.
dns.NOTIMP: DNS server does not implement requested operation.
dns.REFUSED: DNS server refused query.
dns.BADQUERY: Misformatted DNS query.
dns.BADNAME: Misformatted domain name.
dns.BADFAMILY: Unsupported address family.
dns.BADRESP: Misformatted DNS reply.
dns.CONNREFUSED: Could not contact DNS servers.
dns.TIMEOUT: Timeout while contacting DNS servers.
dns.EOF: End of file.
dns.FILE: Error reading file.
dns.NOMEM: Out of memory.
dns.DESTRUCTION: Channel is being destroyed.
dns.BADSTR: Misformatted string.
dns.BADFLAGS: Illegal flags specified.
dns.NONAME: Given hostname is not numeric.
dns.BADHINTS: Illegal hints flags specified.
dns.NOTINITIALIZED: c-ares library initialization not yet performed.
dns.LOADIPHLPAPI: Error loading iphlpapi.dll.
dns.ADDRGETNETWORKPARAMS: Could not find GetNetworkParams function.
dns.CANCELLED: DNS query cancelled.
dns.NODATA: DNS 服务器返回无数据应答。
dns.FORMERR: DNS 声称查询格式错误。
dns.SERVFAIL: DNS 服务器返回一般失败。
dns.NOTFOUND: 域名未找到。
dns.NOTIMP: DNS 服务器未实现所请求操作。
dns.REFUSED: DNS 服务器拒绝查询。
dns.BADQUERY: DNS 查询格式错误。
dns.BADNAME: 域名格式错误。
dns.BADFAMILY: 不支持的地址类型。
dns.BADRESP: DNS 答复格式错误。
dns.CONNREFUSED: 无法联系 DNS 服务器。
dns.TIMEOUT: 联系 DNS 服务器超时。
dns.EOF: 文件末端。
dns.FILE: 读取文件错误。
dns.NOMEM: 超出内存。
dns.DESTRUCTION: 通道正在被销毁。
dns.BADSTR: 字符串格式错误。
dns.BADFLAGS: 指定了非法标记。
dns.NONAME: 所给主机名非数字。
dns.BADHINTS: 指定了非法提示标记。
dns.NOTINITIALIZED: c-ares 库初始化尚未进行。
dns.LOADIPHLPAPI: 加载 iphlpapi.dll 出错。
dns.ADDRGETNETWORKPARAMS: 无法找到 GetNetworkParams 函数。
dns.CANCELLED: DNS 查询取消。

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