I am trying to read and write data to modbus via TCP/IP. I can connect to modbus simulator successfully and read data. But after I cannot close the connection. App says connection closed but when I look at to modbus simulator it does not seem so. What can I do to close my connection?

我正在尝试通过TCP/IP将数据读写到modbus。我可以成功连接到modbus模拟器并读取数据。但在我无法关闭连接之后。应用程序显示连接已关闭，但当我查看modbus模拟器时，似乎并非如此。我该怎么办才能关闭连接？

Because, it's needed to close the connection to read data again and again. What is the solution?

因为，需要关闭连接才能一次又一次地读取数据。解决方案是什么？

import 'dart:async';
import 'package:flutter_riverpod/flutter_riverpod.dart';
import 'package:modbus/modbus.dart' as modbus;
import 'package:flutter_secure_storage/flutter_secure_storage.dart';
import 'package:korubin_modbus/utils/constants.dart';

class RegisterNotifier extends StateNotifier<List<int>> {
  RegisterNotifier() : super([]) {
    // Başlangıçta ve ardından belirli bir süre aralığında veri okuma işlemini başlatın
    startReadingData();
  }


  // Belirli bir süre aralığında veri okuma işlemini başlatan fonksiyon
  Future<void> startReadingData() async {
    const duration = Duration(seconds: 2); // Veri okuma aralığı (2 saniye)
    Timer.periodic(duration, (_) async {
      await readData(); // Veri okuma işlemini çağırın
    });
  }

  Future<String> getIpAddress() async{
    final FlutterSecureStorage secureStorage = FlutterSecureStorage();
    final String ipAddress = await secureStorage.read(key: Constants.ipAddressName) ?? "";
    return ipAddress;
  }


  Future<void> readData() async {
    // Veri okuma işlemini burada gerçekleştirin

    final ipAddress = await getIpAddress();
    if (ipAddress.isEmpty) {
      print('IpAddress is empty');
      return;
    }

    final client = modbus.createTcpClient(ipAddress, port: 502, mode: modbus.ModbusMode.rtu, timeout: Duration(seconds: 5));
    try {
      await client.connect();
      print('Modbus bağlantı kuruldu');

      final registers1 = await client.readHoldingRegisters(0, 100);
      final registers2 = await client.readHoldingRegisters(100, 100);
      final registers3 = await client.readHoldingRegisters(200, 100);

      final List<int> updatedRegisters = [];
      updatedRegisters.addAll(registers1);
      updatedRegisters.addAll(registers2);
      updatedRegisters.addAll(registers3);

      state = updatedRegisters; // Veriyi güncelle
      await client.close();
      print('Okunan tag sayısı: ${updatedRegisters.length}');
    } catch (e) {
      print('Tag okurken hata: ${e.toString()}');
    } finally {
      // await client.close();
      try {
        await client.close();
        print('Modbus connection kapatıldı');
      } catch (e) {
        print('Modbus connection kapatılırken hata oluştu: ${e.toString()}');
      }
    }
  }


  void writeData(int writeIpAddress, int value) async{
    final ipAddress = await getIpAddress();
    final client = modbus.createTcpClient(ipAddress, port: 502, mode: modbus.ModbusMode.rtu, timeout: Duration(seconds: 2));
    try{
      await client.connect();
      print('Yazmak için modbus a bağlandı');

      await client.writeSingleRegister(writeIpAddress - 400001, value);
      print('Tag Address: $writeIpAddress - Veri yazıldı: $value');
    } catch (e) {
      print('Tag yazarken hata: ${e.toString()}');
    } finally {
      await client.close();
      print('Modbus connection kapatıldı');
    }
  }
}

final registerProvider = StateNotifierProvider<RegisterNotifier, List<int>>((ref) => RegisterNotifier());

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Modbus connection close problem

Modbus连接关闭问题