FAQ

ProtoLink 1.1.0 is a local tool for quick checks of Modbus TCP and Modbus RTU devices. It opens in your browser at 127.0.0.1:8000, can read coils, discrete inputs, holding registers, and input registers, and can run single and multiple writes for coils/holding registers. It is not a SCADA system, slave simulator, or historian.

Version 1.1.0 supports FC01, FC02, FC03, FC04, FC05, FC06, FC15, and FC16. For RTU requests, addresses are 0-65535, Unit ID is 1-247, timeout is 0.5-30 seconds, and holding/input register reads support up to 125 registers per request.

For TCP, check the device IP address, port, network reachability, and Unit ID. For RTU, check the COM/serial port, baudrate, parity, stop bits, byte size, Unit ID, device power, RS-485 A/B wiring, and whether another app is using the port.

ProtoLink uses the protocol/data address, which is zero-based. If a device manual lists holding register 40001, you often enter address 0 in ProtoLink and choose FC03.

On Windows, check the USB-RS485 driver and Device Manager. On Linux, check /dev/ttyUSB*, /dev/ttyACM*, or /dev/ttyS* and the dialout group. On macOS, serial devices usually appear as /dev/cu.*.

For packaged builds, Python, Node.js, and npm are not required. Docker is not used for ProtoLink. These tools are only needed when running the project from source for development.

Open 127.0.0.1:8000 in your browser or request 127.0.0.1:8000/api/healthz. In version 1.1.0 the expected response contains {"status":"ok","version":"1.1.0"}.

A timeout means no valid response came back. A Modbus exception means the device received the request but could not process it, such as an unsupported function code, missing register address, or invalid value.

The network scanner is available in version 1.1.0. Automatic Modbus register discovery and float/endianness decoding are not advertised as current features.