DNS-Based service discovery, or DNS-SD (RFC 6763), can be used to discover services on a local area network advertised over Multicast DNS, or mDNS (RFC 6762), enabling peer-to-peer discovery.
This library provides DNS-SD capabilities in Go. To use it, you first create a resolver by specifying the interfaces and address family on which to browse for services.
ifi, err := net.InterfaceByName("en0")
if err != nil {
log.Fatal(err)
}
resolver, err := dnssd.NewResolver(dnssd.AddrFamilyIPv4, []net.Interface{*ifi})
if err != nil {
log.Fatal(err)
}
defer resolver.Close()Next, you provide the names of the services which you wish to browse for to the resolver. The same resolver can be used to browse for multiple services.
resolver.BrowseService("_http._tcp.local.")
resolver.BrowseService("_googlecast._tcp.local.")Finally, you can query the resolver for the set of fully resolved service instances by either retrieving all resolved instances or only instances for a particular service.
instances := resolver.GetAllResolvedInstances()
for _, instance := range instances {
fmt.Printf("%v\n", instance)
}
chromecasts := resolver.GetResolvedInstances("_googlecast._tcp.local.")
for _, instance := range instances {
fmt.Printf("%v\n", instance)
}We can put all of this together to discover all instances of the _http._tcp service on the local network
package main
import (
"fmt"
"log"
"net"
"time"
"github.com/gatkin/dnssd"
)
func main() {
ifi, err := net.InterfaceByName("en0")
if err != nil {
log.Fatal(err)
}
resolver, err := dnssd.NewResolver(dnssd.AddrFamilyIPv4, []net.Interface{*ifi})
if err != nil {
log.Fatal(err)
}
defer resolver.Close()
resolver.BrowseService("_http._tcp.local.")
resolver.BrowseService("_googlecast._tcp.local.")
// Wait some time to allow all service instances to be discovered.
time.Sleep(1 * time.Second)
instances := resolver.GetAllResolvedInstances()
for _, instance := range instances {
fmt.Printf("%v\n", instance)
}
}
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