~

src/src/main/java/com/my/graphiteDigesterBg/diframe/connection/DiConModbusRTUOverTCP.java

@@ -71,6 +71,9 @@ public class DiConModbusRTUOverTCP {
         cmd[4] = 0x00; // value high
         cmd[5] = 0x01; // value low
         var response = this.call(cmd);
+        if (response.isEmpty()) {
+            throw new RuntimeException("Modbus RTU over TCP: no response");
+        }
         return response.get(3) << 8 | response.get(4);
     }