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I would like to use flutter to design a modbus tcp procedure on web plate form.
But i don’t know how to start.
I saw the package( https://pub.dev/packages/modbus)(https://pub.dev/packages/modbus_client)，and want to try it, but it didn’t work on web plate form.
Could any one show me a simple example or have experience to share, thank you.

I tried use package modbus .
But didn’t work on web plate form.
The below code can used on windows plateform，but if run debug on chrome，connect fail:

import 'package:flutter/material.dart';
import 'package:modbus_client/modbus_client.dart';
import 'package:modbus_client_tcp/modbus_client_tcp.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  final TextEditingController _ipController = TextEditingController();
  final TextEditingController _portController = TextEditingController();
  final TextEditingController _registerController = TextEditingController();
  String _result = '';

  Future<void> _readHoldingRegister() async {
    final ip = _ipController.text;
    final port = int.tryParse(_portController.text) ?? 502;
    final registerAddress = int.tryParse(_registerController.text) ?? 0;
    var battery = ModbusInt16Register(
      name: "Battery",
      type: ModbusElementType.inputRegister,
      address: 4098,
      uom: "V",
      multiplier: 0.1,
      onUpdate: (self) => print(self));
    try {
      // Initialize Modbus client
      var client =  ModbusClientTcp (
        ip,
        serverPort: port,
        unitId: 15,  //  unitId
        responseTimeout :const Duration(seconds: 3),
        connectionMode: ModbusConnectionMode.autoConnectAndDisconnect,
      );

      // Connect to the Modbus server
      final connected = await client.connect();
      if (!connected) {
        setState(() {
          _result = 'Failed to connect to the server';
        });
        return;
      }

      // Create a Modbus request to read holding registers
      final request = battery.getReadRequest();

      // Send the request
      final responseCode = await client.send(request);

      // Check the response code
      if (responseCode == ModbusResponseCode.requestSucceed) {
        // Read the register value
        final result = await client.send(request);
        setState(() {
          _result = 'Register value: ${battery.value}';
        });
      } else {
        setState(() {
          _result = 'Error: ${responseCode.code}';
        });
      }

      // Disconnect after request
      await client.disconnect();
    } catch (e) {
      setState(() {
        _result = 'Exception: $e';
      });
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Modbus TCP Reader'),
      ),
      body: Padding(
        padding: const EdgeInsets.all(16.0),
        child: Column(
          children: [
            TextField(
              controller: _ipController,
              decoration: InputDecoration(labelText: 'IP Address'),
            ),
            TextField(
              controller: _portController,
              decoration: InputDecoration(labelText: 'Port'),
              keyboardType: TextInputType.number,
            ),
            TextField(
              controller: _registerController,
              decoration: InputDecoration(labelText: 'Register Address'),
              keyboardType: TextInputType.number,
            ),
            SizedBox(height: 20),
            ElevatedButton(
              onPressed: _readHoldingRegister,
              child: Text('Read Register'),
            ),
            SizedBox(height: 20),
            Text(_result),
          ],
        ),
      ),
    );
  }
}