引入NModbus

dotnet add package NModbus --version 3.0.81

Program.cs

using IOT.Common;
using NModbus;
using System.Net.Sockets;
using System.Net;


var dataStore = ModbusSlaveDataStore.Instance;
_ = Task.Run(() => {
    StartListen(dataStore);
});
await Task.Delay(1000);

// 循环写入点位值
_ = Task.Run(async () =>
{
    do
    {
        ushort startAddr = 0;

        var f1 = Random.Shared.Next(1, 500) * 2.25;
        WriteFloatPoints(dataStore.InputRegisters, startAddr, (float)f1);

        var f2 = (ushort)Random.Shared.Next(1, 999);
        dataStore.InputRegisters.WritePoints((ushort)(startAddr + 2), [f2]);

        await Task.Delay(500);
    } while (true);
});


// 一秒读取一次点位值
List<string> nodes = [
    "1,0,2","1,2,1"
    ];
do
{
    var values = await ModbusTcpHelper.Instance.ReadModbusTcpServer("localhost", nodes);
    foreach (var (k, v) in values)
    {
        if (v.Contains(","))
        {
            var arr = v.Split(",");
            var low = ushort.Parse(arr[0]);
            var high = ushort.Parse(arr[1]);
            var floatValue = ReadFloatPoint(low, high);
            Console.WriteLine($"{k}: {floatValue}");
        }
        else
        {
            Console.WriteLine($"{k}: {v}");
        }
    }
    await Task.Delay(1000);
} while (true);



void WriteFloatPoints(IPointSource<ushort> left, ushort startAddress, float value)
{
    var bytes = BitConverter.GetBytes(value);
    ushort lowOrderValue = BitConverter.ToUInt16(bytes, 0);
    ushort highOrderValue = BitConverter.ToUInt16(bytes, 2);
    ushort[] registers = [lowOrderValue, highOrderValue];
    left.WritePoints(startAddress, registers);
}

float ReadFloatPoint(ushort low,ushort high)
{
    var bytes = new byte[4];
    BitConverter.GetBytes(low).CopyTo(bytes, 0);
    BitConverter.GetBytes(high).CopyTo(bytes, 2);
    float value = BitConverter.ToSingle(bytes, 0);
    return value;
}

void StartListen(ModbusSlaveDataStore slaveDataStore)
{
    // 创建TCP监听器
    int port = 502;
    TcpListener tcpListener = new TcpListener(IPAddress.Any, port);
    tcpListener.Start();

    // 创建Modbus工厂
    IModbusFactory modbusFactory = new ModbusFactory();

    // 创建服务器网络流
    var modbusSlaveNetwork = modbusFactory.CreateSlaveNetwork(tcpListener);

    // 添加从站ID 1
    var slave = modbusFactory.CreateSlave(1, slaveDataStore);
    modbusSlaveNetwork.AddSlave(slave);

    // 启动Modbus服务器
    modbusSlaveNetwork.ListenAsync();

    // 打印启动信息
    Console.WriteLine($"Modbus TCP Server is listening on port {port}");
    Console.ReadKey();

    // 停止服务器
    tcpListener.Stop();
}

public class ModbusSlaveDataStore : ISlaveDataStore
{
    private static readonly object _lock = new object();
    private static ModbusSlaveDataStore? _instance;
    public static ModbusSlaveDataStore Instance
    {
        get
        {
            lock (_lock)
            {
                _instance = _instance ??= new ModbusSlaveDataStore();
                return _instance;
            }
        }
    }

    private readonly ushort[] _holdingRegisters = new ushort[100];
    private readonly ushort[] _inputRegisters = new ushort[100];
    private readonly bool[] _coilDiscretes = new bool[100];
    private readonly bool[] _inputDiscretes = new bool[100];

    public IPointSource<bool> CoilDiscretes => new DiscretePointSource(_coilDiscretes);

    public IPointSource<bool> CoilInputs => new DiscretePointSource(_inputDiscretes);

    public IPointSource<ushort> HoldingRegisters => new RegisterPointSource(_holdingRegisters);

    public IPointSource<ushort> InputRegisters => new RegisterPointSource(_inputRegisters);

    private class RegisterPointSource : IPointSource<ushort>
    {
        private readonly ushort[] _registers;
        public RegisterPointSource(ushort[] registers) => _registers = registers;

        public ushort[] ReadPoints(ushort startAddress, ushort numberOfPoints)
        {
            ushort[] points = new ushort[numberOfPoints];
            Array.Copy(_registers, startAddress, points, 0, numberOfPoints);
            return points;
        }

        public void WritePoints(ushort startAddress, ushort[] values)
        {
            Array.Copy(values, 0, _registers, startAddress, values.Length);
        }
    }


    private class DiscretePointSource : IPointSource<bool>
    {
        private readonly bool[] _discretes;
        public DiscretePointSource(bool[] discretes) => _discretes = discretes;

        public bool[] ReadPoints(ushort startAddress, ushort numberOfPoints)
        {
            bool[] points = new bool[numberOfPoints];
            Array.Copy(_discretes, startAddress, points, 0, numberOfPoints);
            return points;
        }

        public void WritePoints(ushort startAddress, bool[] values)
        {
            Array.Copy(values, 0, _discretes, startAddress, values.Length);
        }
    }
}

ModbusTcpHelper.cs

using NModbus;
using NModbus.Device;
using NModbus.IO;
using Serilog;
using System.Net.Sockets;

namespace IOT.Common;

/// <summary>
/// 单例
/// </summary>
public class ModbusTcpHelper
{
    static readonly object _lock = new object();
    private static ModbusTcpHelper? _instance;
    public static ModbusTcpHelper Instance
    {
        get
        {
            lock (_lock)
            {
                _instance = _instance ?? new ModbusTcpHelper();
                return _instance;
            }
        }
    }

    public async Task<Dictionary<string, string>> ReadModbusTcpServer(string ipAddress, List<string> attrIds, int port = 502)
    {
        Dictionary<string, string> keyValuePairs = new Dictionary<string, string>();
        try
        {
            // 创建Modbus TCP客户端
            TcpClient tcpClient = new TcpClient(ipAddress, port);
            IStreamResource streamResource = new TcpClientAdapter(tcpClient);
            ModbusIpTransport transport = new ModbusIpTransport(streamResource, new ModbusFactory(), new CustomModbusLogger());
            // 创建 Modbus TCP 主站实例
            ModbusIpMaster master = new ModbusIpMaster(transport);
            try
            {
                Log.Information($"attrIds Value: " + string.Join(",", attrIds));
                foreach (var attrId in attrIds)
                {
                    var attrIdArr = attrId.Split(",");
                    if (attrIdArr.Length > 2) {
                        ///从站地址
                        byte slaveId = byte.Parse(attrIdArr[0]);
                        // 寄存器起始地址
                        ushort startAddress = Convert.ToUInt16(attrIdArr[1], 16); // 注意这里是16进制
                        // 寄存器地址长度
                        ushort numOfPoints = ushort.Parse(attrIdArr[2]);
                        // 读取 DI3 对应的寄存器值
                        ushort[] inputs = master.ReadInputRegisters(slaveId, startAddress, numOfPoints);
                        Log.Information($"{nameof(ModbusTcpHelper)}: {startAddress} read is {string.Join(",", inputs)}");
                        keyValuePairs.Add(attrId.ToString(),string.Join(',',inputs));
                    }
                }
            }
            catch (Exception ex)
            {
                Log.Error($"{nameof(ModbusTcpHelper)}: [{ipAddress}] {ex}");
            }
            finally
            {
                // 关闭连接
                tcpClient.Close();
                master.Dispose();
            }
        }
        catch (Exception ex)
        {
            Log.Error($"{nameof(ModbusTcpHelper)}: [{ipAddress}] {ex}");
        }
        return keyValuePairs;
    }
}

public class CustomModbusLogger : IModbusLogger
{
    public bool ShouldLog(LoggingLevel level)
    {
        return true;
    }

    void IModbusLogger.Log(LoggingLevel level, string message)
    {
        if(level !=  LoggingLevel.Error)return;

        Log.Error($"{nameof(ModbusTcpHelper)}: {message}");
        //Console.WriteLine($"Function Code: {level}, Data: {message}");
    }
}

Preview

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