C#实现MQTT到ModbusRTU数据转发的完整方案

方案概述
本方案将使用MQTTnet库接收MQTT消息，并通过NModbus库将处理后的数据写入ModbusRTU设备。整个流程分为MQTT客户端实现、ModbusRTU主站实现和数据转换三个主要部分

1. 环境准备
   首先需要安装必要的NuGet包：

MQTTnet (版本4.3.7或更高)
NModbus (版本2.1.0或更高)
System.IO.Ports (用于串口通信)
安装命令：
dotnet add package MQTTnet
dotnet add package NModbus
2. MQTT客户端实现
以下是创建MQTT客户端并订阅主题的基本代码框架：
`
using MQTTnet;
using MQTTnet.Client;
using MQTTnet.Client.Options;
using System;
using System.Text;
using System.Threading.Tasks;

public class MqttClientService
{
private IMqttClient _mqttClient;
private readonly string _brokerAddress;
private readonly int _brokerPort;
private readonly string _topic;

public MqttClientService(string brokerAddress, int brokerPort, string topic)
{
    _brokerAddress = brokerAddress;
    _brokerPort = brokerPort;
    _topic = topic;
}

public async Task ConnectAsync()
{
    var factory = new MqttFactory();
    _mqttClient = factory.CreateMqttClient();
    
    var options = new MqttClientOptionsBuilder()
        .WithTcpServer(_brokerAddress, _brokerPort)
        .WithClientId("ModbusGateway")
        .Build();

    _mqttClient.UseApplicationMessageReceivedHandler(HandleReceivedMessage);
    
    await _mqttClient.ConnectAsync(options);
    await _mqttClient.SubscribeAsync(new TopicFilterBuilder().WithTopic(_topic).Build());
}

private void HandleReceivedMessage(MqttApplicationMessageReceivedEventArgs e)
{
    var payload = Encoding.UTF8.GetString(e.ApplicationMessage.Payload);
    // 这里将调用Modbus写入逻辑
    ModbusWriter.WriteToDevice(payload);
}

}MqttClientService.cs这段代码创建了一个MQTT客户端，连接到指定代理并订阅主题，收到消息后会调用Modbus写入逻辑 3. ModbusRTU主站实现 以下是ModbusRTU主站的实现代码： NModbus;
using System.IO.Ports;

public class ModbusRtuService
{
private SerialPort _serialPort;
private IModbusSerialMaster _modbusMaster;

public void Initialize(string portName, int baudRate = 9600, 
    Parity parity = Parity.None, int dataBits = 8, 
    StopBits stopBits = StopBits.One)
{
    _serialPort = new SerialPort(portName, baudRate, parity, dataBits, stopBits);
    _serialPort.Open();
    
    var factory = new ModbusFactory();
    _modbusMaster = factory.CreateRtuMaster(_serialPort);
}

public void WriteSingleRegister(byte slaveAddress, ushort startAddress, ushort value)
{
    _modbusMaster.WriteSingleRegister(slaveAddress, startAddress, value);
}

public void WriteMultipleRegisters(byte slaveAddress, ushort startAddress, ushort[] values)
{
    _modbusMaster.WriteMultipleRegisters(slaveAddress, startAddress, values);
}

}ModbusRtuService.cs这段代码初始化了ModbusRTU主站，提供了写入单个寄存器和多个寄存器的方法 4. 数据转换与集成 将MQTT消息转换为Modbus寄存器值的核心逻辑：using System;
using System.Text.Json;

public static class ModbusWriter
{
private static ModbusRtuService _modbusService = new ModbusRtuService();

public static void InitializeModbus(string portName)
{
    _modbusService.Initialize(portName);
}

public static void WriteToDevice(string mqttPayload)
{
    try
    {
        // 假设MQTT消息是JSON格式，包含设备地址和寄存器值
        var message = JsonSerializer.Deserialize<ModbusMessage>(mqttPayload);
        
        if (message.RegisterValues.Length == 1)
        {
            _modbusService.WriteSingleRegister(
                message.SlaveAddress, 
                message.StartAddress, 
                message.RegisterValues[0]);
        }
        else
        {
            _modbusService.WriteMultipleRegisters(
                message.SlaveAddress, 
                message.StartAddress, 
                message.RegisterValues);
        }
    }
    catch (Exception ex)
    {
        // 错误处理逻辑
    }
}

}

public class ModbusMessage
{
public byte SlaveAddress { get; set; }
public ushort StartAddress { get; set; }
public ushort[] RegisterValues { get; set; }
}
ModbusWriter.cs这段代码将JSON格式的MQTT消息解析为Modbus写入命令 5. 主程序集成 最后将各部分集成到主程序中： System;
using System.Threading.Tasks;

class Program
{
static async Task Main(string[] args)
{
// 初始化ModbusRTU服务
ModbusWriter.InitializeModbus("COM3"); // 根据实际串口修改

    // 创建并启动MQTT客户端
    var mqttService = new MqttClientService("broker.example.com", 1883, "modbus/commands");
    await mqttService.ConnectAsync();
    
    Console.WriteLine("服务已启动，按任意键退出...");
    Console.ReadKey();
}

}`
Program.cs代码实现集成应用。