Correct HTTPU serving to not require an interface for multicast.

cmd/example_httpu_serving/example_httpu_serving.go

@@ -2,24 +2,19 @@ package main
 
 import (
 	"log"
-	"net"
 	"net/http"
 
 	"github.com/huin/goupnp/httpu"
 )
 
 func main() {
-	eth0, err := net.InterfaceByName("eth0")
-	if err != nil {
-		log.Fatal(err)
-	}
 	srv := httpu.Server{
 		Addr:      "239.255.255.250:1900",
-		Interface: eth0,
+		Multicast: true,
 		Handler: httpu.HandlerFunc(func(r *http.Request) {
 			log.Printf("Got %s %s message from %v: %v", r.Method, r.URL.Path, r.RemoteAddr, r.Header)
 		}),
 	}
-	err = srv.ListenAndServe()
+	err := srv.ListenAndServe()
 	log.Printf("Serving failed with error: %v", err)
 }