diff --git a/config/config.go b/config/config.go
index 7374a58..5c62942 100644
--- a/config/config.go
+++ b/config/config.go
@@ -23,11 +23,11 @@ func IsNet(host string) (bool, string) {
 		// E.g., "[fe80::1]:80".
 		i := strings.LastIndex(host, "]")
 		if i < 0 {
-			log.Fatal("Unmatched [ in destination config")
+			log.Println("Unmatched [ in destination config")
 			return false, ""
 		}
 		if !validPort(host[i+1:]) {
-			log.Fatal("No valid port specified")
+			log.Println("No valid port specified")
 			return false, ""
 		}
 		// trim brackets
@@ -36,21 +36,27 @@ func IsNet(host string) (bool, string) {
 		}
 	} else {
 		// Ipv4 or DNS name
-		ss := strings.Split(string(host), ":")
+		ss := strings.Split(host, ":")
 		if len(ss) > 1 {
 			if !validPort(":" + ss[1]) {
-				log.Fatal("No valid port specified")
+				log.Println("No valid port specified")
 				return false, ""
 			}
+			// if not nil, its a valid IP adress
 			if net.ParseIP(ss[0]) != nil {
 				return true, host
 			}
-            if validDNS.MatchString(ss[0]) {
+			// if "localhost", its valid
+			if strings.Compare("localhost", ss[0]) == 0 {
+				return true, host
+			}
+			// check against the regex
+			if validDNS.MatchString(ss[0]) {
 				return true, host
 			} else {
-				log.Fatal(fmt.Sprintf("DNS/IP: %s, Server Port: %s\n", ss[0], ss[1]))
-				return false,  ""
-            }
+				log.Println(fmt.Sprintf("DNS/IP: %s, Server Port: %s", ss[0], ss[1]))
+				return false, ""
+			}
 		}
 	}
 	return false, host
@@ -93,7 +99,7 @@ func ReadConfigFile(folder string, fileName string) []byte {
 		log.Fatal(err)
 	}
 
-    // trim \r and \n if present
-    r := bytes.TrimSuffix(data[:count], []byte("\n"))
-    return bytes.TrimSuffix(r, []byte("\r"))
+	// trim \r and \n if present
+	r := bytes.TrimSuffix(data[:count], []byte("\n"))
+	return bytes.TrimSuffix(r, []byte("\r"))
 }
diff --git a/d4-golang-utils_test.go b/d4-golang-utils_test.go
new file mode 100644
index 0000000..69bb960
--- /dev/null
+++ b/d4-golang-utils_test.go
@@ -0,0 +1,38 @@
+package main
+
+import (
+	"testing"
+
+	config "github.com/D4-project/d4-golang-utils/config"
+)
+
+var testCases = []struct {
+	name     string
+	str      string
+	expected bool
+}{
+	{"Well-formed IPv4 with port", "127.0.0.1:4443", true},
+	{"Well-formed IPv4 without port", "127.0.0.1", false},
+	{"Malformed IPv4 with port", "127..0.1:4443", false},
+	{"Malformed IPv4 without port", "127..0.1", false},
+	{"Well-formed IPv6 with port - 2", "[::1]:4443", true},
+	{"Well-formed IPv6 without port", "[fe80::1%25en0]", false},
+	{"Malformed IPv6 with port", "[::::1]:4443", false},
+	{"Malformed IPv6 without port", "[::::::::1]", false},
+	{"Malformed IPv6 : missing square brackets", "::::::::1:4443", false},
+	{"Well-formed DNS name with port", "toto.circl.lu:4443", true},
+	{"Well-formed DNS name without port", "toto.circl.lu", false},
+	{"Malformed DNS name with port", ".:4443", false},
+	{"Localhost with port", "localhost:4443", true},
+}
+
+func TestIsNet(t *testing.T) {
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			b, _ := config.IsNet(tc.str)
+			if b != tc.expected {
+				t.Fail()
+			}
+		})
+	}
+}