Check key range

frontend/headless/main.go

@@ -70,11 +70,14 @@ func main() {
 		case "key":
 			if len(parts) < 2 {
 				fmt.Println("Usage: key <number>")
-			} else if code, err := strconv.Atoi(parts[1]); err != nil {
-				fmt.Println("Usage: key <number>")
+			} else {
+				code, err := strconv.Atoi(parts[1])
+				if err != nil || code < 0 || code > 127 {
+					fmt.Println("Usage: key <number from 0 to 127>")
 				} else {
 					fe.putKey(uint8(code))
 				}
+			}
 		case "type":
 			text := strings.Join(parts[1:], " ")
 			for _, char := range text {