Modbus RTU Server

Modbus RTU Server is an Android USB serial Modbus RTU server and Modbus slave test app for engineers who need to open a Modbus RTU server, monitor live values, and set coil or register data from a phone or tablet. It fits PLC testing, HMI integration checks, industrial device debugging, field commissioning, and USB serial or USB to RS485 workflows.

Scan USB serial devices, request USB permission, open the serial port, and configure baud rate, data bits, parity, stop bits, timeout, and slave ID. View and set FC01 Coil, FC02 Discrete Input, FC03 Holding Register, and FC04 Input Register values with start address and length controls. If you are searching for a Modbus RTU simulator, Modbus slave tester, register tester, coil tester, or USB serial Modbus tool, this app targets that workflow.

Key features
- USB serial device scan and selection
- Modbus RTU server open and connection status
- Baud rate, data bits, parity, stop bits, timeout, and slave ID setup
- FC01 Coil read and set
- FC02 Discrete Input view and set
- FC03 Holding Register read and set
- FC04 Input Register view and set
- Start address and length based data view
- Live refresh for fast testing
- USB detach detection and clean disconnect
- Saved serial settings
- Auto driver plus manual driver selection for Prolific, FTDI, QinHeng, and SiliconLabs

Best for
- Modbus RTU slave testing
- PLC, HMI, sensor, meter, and controller communication checks
- USB serial or USB to RS485 field testing
- Coil and register simulation during commissioning and debugging

Open a Modbus RTU server faster and run USB serial Modbus tests on Android.