code: static public boolean checkServerAddress(int serverAddress) {
          /*
          * hook for server address is equals zero:
          * some of modbus tcp slaves sets the UnitId value to zero, not ignoring value in this field.
          */
          switch (serverAddress) {
              case 0x00:
                  //Modbus.log().info("Broadcast message");
                  return true;
              case 0xFF:
                  //Modbus.log().info("Using 0xFF ModbusTCP default slave id");
                  return true;
              default:
                  return !(serverAddress < Modbus.MIN_SERVER_ADDRESS || serverAddress > Modbus.MAX_SERVER_ADDRESS);
          }
      }
docs: validates address of server
  
  @param serverAddress - The modbus server address
  @return "true" if serverAddress is correct, else "false".