Standard library · The network

net/dns

Imported as import "net/dns" as dns, its names are then dns.…. Every signature below is the one the checker infers.

Functions

fn lookup(name: Str) -> Result(List(Str), Str)

Every address the name has, IPv4 addresses first and then IPv6, or why there are none.

res_map(dns.lookup("localhost"), \addrs -> any(addrs, \a -> a == "127.0.0.1"))   # => Ok(true)
res_map(dns.lookup("no.such.host.invalid"), \addrs -> len(addrs))            # => Err(`no.such.host.invalid` is not a name the resolver knows)

fn ipv4(name: Str) -> Option(Str)

The first IPv4 address, which is what tcp_connect and udp.send_to take.

dns.ipv4("localhost")   # => Some(127.0.0.1)

fn is_ipv4(s: Str) -> Bool

Four numbers of at most three digits, each below 256, with dots between.

dns.is_ipv4("192.168.0.1")   # => true
dns.is_ipv4("256.1.1.1")     # => false
dns.is_ipv4("::1")           # => false

Tests

• test_localhost_and_literals
• test_an_unknown_name