diff --git a/whoami.go b/whoami.go
index 5dbea1e..81c0b05 100644
--- a/whoami.go
+++ b/whoami.go
@@ -3,38 +3,49 @@ package main
 import (
 	"net/http"
 	"net"
-	"strings"	
         "encoding/base32"
-	"os"
+	"strings"
+	"flag"
 )
 
-// DomainFromIP derives a meshname subdomain for the authoritative DNS server address
-func DomainFromIP(target net.IP) string {
+
+// define tld
+var tld = flag.String("tld", "mesh.cat", "The top level domain for our network")
+
+// domainFromIP derives a meshname subdomain for the authoritative DNS server address
+func domainFromIP(target net.IP) string {
         host := strings.ToLower(base32.StdEncoding.EncodeToString(target)[0:26])
-	tld := ".mesh.cat"
-	domain := strings.Join([]string{host, tld}, "")
+	domain := strings.Join([]string{host, ".", *tld, "\n"}, "")
 	return domain
 }
 
+// handle HTTP requests
 func handler(w http.ResponseWriter, r *http.Request) {
 	ip, port, err := net.SplitHostPort(r.RemoteAddr)
 	_, _ = port, err	
 	parsedIP := net.ParseIP(ip)
 	// return domain for IPv6 only
 	if parsedIP.To4() == nil {
-		w.Write([]byte(DomainFromIP(parsedIP)))
+		w.Write([]byte(domainFromIP(parsedIP)))
+	} else {
+		// set the response status code to 422
+		w.WriteHeader(http.StatusUnprocessableEntity)
+		w.Write([]byte("ipv4 not supported\n"))
 	}
 }
 
 func main() {
+	// define path
 	http.HandleFunc("/", handler)
-	listenPort := "3000"
-	// Get the first command-line argument
-	if len(os.Args) > 1 {
-		listenPort = os.Args[1]
-	}
-	print("Listening on port: ", listenPort, "\n")
-	listenPort = strings.Join([]string{":", listenPort}, "")
-	http.ListenAndServe(listenPort, nil)
+	// define ip address
+	address := flag.String("address", "[::0]", "The interface address to listen on")
+	// define port
+	port := flag.String("port", "8008", "The port to listen on")
+	// parse the command-line arguments
+	flag.Parse()
+	// construct listening address
+	listenAddr := strings.Join([]string{*address, ":", *port}, "")
+	print("Listening on address: ", listenAddr, "\n")
+	// start server
+	http.ListenAndServe(listenAddr, nil)
 }
-