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< article >
< h1 > dns</ h1 >
< p > The < code > dns</ code > module provides DNS resolution functionality for looking up hostnames and resolving them to IP addresses.</ p >
< pre >< code > import "dns" for Dns</ code ></ pre >
< h2 > Dns Class</ h2 >
< div class = "class-header" >
< h3 > Dns</ h3 >
< p > DNS resolution utilities</ p >
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< h3 > Static Methods</ h3 >
< div class = "method-signature" >
< span class = "method-name" > Dns.lookup</ span > (< span class = "param" > hostname</ span > ) → < span class = "type" > String</ span >
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< p > Resolves a hostname to an IP address. Uses the system's default address family preference.</ p >
< ul class = "param-list" >
< li >< span class = "param-name" > hostname</ span > < span class = "param-type" > (String)</ span > - Hostname to resolve</ li >
< li >< span class = "returns" > Returns:</ span > IP address as a string</ li >
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< pre >< code > var ip = Dns.lookup("example.com")
System.print(ip) // 93.184.216.34</ code ></ pre >
< div class = "method-signature" >
< span class = "method-name" > Dns.lookup</ span > (< span class = "param" > hostname</ span > , < span class = "param" > family</ span > ) → < span class = "type" > String</ span >
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< p > Resolves a hostname to an IP address with a specific address family.</ p >
< ul class = "param-list" >
< li >< span class = "param-name" > hostname</ span > < span class = "param-type" > (String)</ span > - Hostname to resolve</ li >
< li >< span class = "param-name" > family</ span > < span class = "param-type" > (Num)</ span > - Address family: 0 (any), 4 (IPv4), or 6 (IPv6)</ li >
< li >< span class = "returns" > Returns:</ span > IP address as a string</ li >
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< pre >< code > var ipv4 = Dns.lookup("example.com", 4)
System.print(ipv4) // 93.184.216.34
var ipv6 = Dns.lookup("example.com", 6)
System.print(ipv6) // 2606:2800:220:1:248:1893:25c8:1946</ code ></ pre >
< h3 > Address Family Values</ h3 >
< table >
< tr >
< th > Value</ th >
< th > Description</ th >
</ tr >
< tr >
< td >< code > 0</ code ></ td >
< td > Any (system default, typically prefers IPv4)</ td >
</ tr >
< tr >
< td >< code > 4</ code ></ td >
< td > IPv4 only</ td >
</ tr >
< tr >
< td >< code > 6</ code ></ td >
< td > IPv6 only</ td >
</ tr >
</ table >
< h2 > Examples</ h2 >
< h3 > Basic DNS Lookup</ h3 >
< pre >< code > import "dns" for Dns
var domains = ["example.com", "google.com", "github.com"]
for (domain in domains) {
var ip = Dns.lookup(domain)
System.print("%(domain) -> %(ip)")
}</ code ></ pre >
< h3 > IPv4 vs IPv6</ h3 >
< pre >< code > import "dns" for Dns
var hostname = "google.com"
var ipv4 = Dns.lookup(hostname, 4)
System.print("IPv4: %(ipv4)")
var fiber = Fiber.new {
return Dns.lookup(hostname, 6)
}
var result = fiber.try()
if (fiber.error != null) {
System.print("IPv6: Not available")
} else {
System.print("IPv6: %(result)")
}</ code ></ pre >
< h3 > Using with Socket Connection</ h3 >
< pre >< code > import "dns" for Dns
import "net" for Socket
var hostname = "httpbin.org"
var ip = Dns.lookup(hostname, 4)
System.print("Connecting to %(hostname) (%(ip))")
var socket = Socket.connect(ip, 80)
socket.write("GET /ip HTTP/1.1\r\nHost: %(hostname)\r\nConnection: close\r\n\r\n")
var response = ""
while (true) {
var data = socket.read()
if (data == null) break
response = response + data
}
socket.close()
System.print(response)</ code ></ pre >
< h3 > Using with TLS Connection</ h3 >
< pre >< code > import "dns" for Dns
import "tls" for TlsSocket
var hostname = "example.com"
var ip = Dns.lookup(hostname, 4)
var socket = TlsSocket.connect(ip, 443, hostname)
socket.write("GET / HTTP/1.1\r\nHost: %(hostname)\r\nConnection: close\r\n\r\n")
var response = socket.read()
System.print(response)
socket.close()</ code ></ pre >
< h3 > Error Handling</ h3 >
< pre >< code > import "dns" for Dns
var fiber = Fiber.new {
return Dns.lookup("nonexistent.invalid.domain")
}
var result = fiber.try()
if (fiber.error != null) {
System.print("DNS lookup failed: %(fiber.error)")
} else {
System.print("Resolved to: %(result)")
}</ code ></ pre >
< div class = "admonition note" >
< div class = "admonition-title" > Note</ div >
< p > DNS lookups are asynchronous operations that use libuv's thread pool. The calling fiber will suspend until the lookup completes.</ p >
</ div >
< div class = "admonition warning" >
< div class = "admonition-title" > Warning</ div >
< p > The hostname must be a string. Passing a non-string value will abort the fiber with an error. Similarly, the family parameter must be 0, 4, or 6.</ p >
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