Java Modbus RTU connectivity using RS485 to USB converter

I have 20 Modbus devices (Rs-485) connected to ATC -820 Converter (its just simple RS485-USB converter) using multi hopping. These devices have ID (serial number) 1 to 20 in sequence. Each Device will have 10 parameters (memory locations - holding registers) to read. I have to save data is mySql data base will following table structure with timestamp I want to read data every second from all these Devices using JAVA, multi threading. As I have single device for testing. So as of now Code can be tested on 1 device and can be tested for rest of the devices on site at client end. Support will needed to test it at client end after lock down period is over. SQL Table structure DROP TABLE IF EXISTS `dl_eventlog_dtpew`; CREATE TABLE `dl_eventlog_dtpew` ( `id` bigint(50) NOT NULL, `event_time_epoch` LONG NOT NULL, `event_time` timestamp NOT NULL DEFAULT '1990-01-01 00:00:00', `line_id` int(10) DEFAULT NULL, `machine_id` int(10) DEFAULT NULL, `dt` varchar(15) DEFAULT NULL, `tm` varchar(15) DEFAULT NULL, `mould_id` int(11) DEFAULT NULL, `left_power_d1` int(1) DEFAULT NULL, `left_emergency_d2` int(1) DEFAULT NULL, `left_temp_top_t1` int(1) DEFAULT NULL, `left_temp_bottom_t2` int(1) DEFAULT NULL, `left_pressure_p1` float DEFAULT NULL, `right_power_d3` int(1) DEFAULT NULL, `right_emergency_d4` int(1) DEFAULT NULL, `right_temp_top_t3` int(1) DEFAULT NULL, `right_temp_bottom_t4` int(1) DEFAULT NULL, `right_pressure_p2` float DEFAULT NULL, `uploaded` varchar(4) NOT NULL DEFAULT 'N' ) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=latin1;