diff --git a/utils/ip_test.go b/utils/ip_test.go
index a9ab956..04cb9e6 100644
--- a/utils/ip_test.go
+++ b/utils/ip_test.go
@@ -62,3 +62,22 @@ func TestIPDescEqual(t *testing.T) {
 		})
 	}
 }
+
+func TestIPDescPortString(t *testing.T) {
+	tests := []struct {
+		ipDesc IPDesc
+		result string
+	}{
+		{IPDesc{net.ParseIP("127.0.0.1"), 0}, ":0"},
+		{IPDesc{net.ParseIP("::1"), 42}, ":42"},
+		{IPDesc{net.ParseIP("::ffff:127.0.0.1"), 65535}, ":65535"},
+		{IPDesc{net.IP{}, 1234}, ":1234"},
+	}
+	for _, tt := range tests {
+		t.Run(tt.result, func(t *testing.T) {
+			if result := tt.ipDesc.PortString(); result != tt.result {
+				t.Errorf("Expected %q, got %q", tt.result, result)
+			}
+		})
+	}
+}