ProtoLink 1.4.0
Troubleshooting
A practical checklist for local launch and diagnostics
The web interface does not open
- Make sure ProtoLink is running.
- Open http://127.0.0.1:8000 manually.
- Check /api/healthz — the expected version is 1.4.0.
- If port 8000 is busy, close the process using it and restart ProtoLink.
Modbus TCP does not respond
- Check the IP address, TCP port, and device reachability from the current network.
- Verify the Unit ID and data type: coils, discrete inputs, input registers, or holding registers.
- Lower the value count and increase the timeout on an unstable link.
Modbus RTU does not respond
- Check the COM/serial port, baud rate, parity, stop bits, and byte size.
- Verify the Unit ID and close other applications that may use the port.
- Check A/B lines, GND, adapter power, and RS‑485 parameters.
The serial port is missing
- Windows: check the COM port in Device Manager.
- Linux: check /dev/ttyUSB* or /dev/ttyACM* and the user’s dialout group membership.
- macOS: outbound connections normally use a /dev/cu.* device.
Values look wrong
- Verify zero-based versus one-based addressing in the device documentation.
- Select the correct register type and function code.
- For multi-register values, check byte order and word swap.
- Compare HEX and DEC to separate formatting issues from a wrong address.
Writes fail
- Check whether the device allows writes to the selected address.
- Verify the value range, register type, and function code.
- For multiple writes, verify the starting address and the complete value list.
Need more help?
Send the error text and connection settings