一、环境配置与依赖安装
# NuGet包安装（支持.NET Framework 4.5+）
Install-Package NModbus4
Install-Package System.IO.Ports
二、核心代码实现
1. 串口初始化与连接
using System.IO.Ports;
using Modbus.Device;
public class ModbusRtuMaster
{
private SerialPort _serialPort;
private IModbusSerialMaster _master;
public void Connect(string portName, int baudRate = 9600, Parity parity = Parity.None,
int dataBits = 8, StopBits stopBits = StopBits.One)
{
try
{
_serialPort = new SerialPort(portName, baudRate, parity, dataBits, stopBits)
{
ReadTimeout = 3000,
WriteTimeout = 3000
};
_serialPort.Open();
_master = ModbusSerialMaster.CreateRtu(_serialPort);
_master.Transport.Retries = 3; // 设置重试次数
_master.Transport.WriteTimeout = 2000;
_master.Transport.ReadTimeout = 2000;
}
catch (Exception ex)
{
Console.WriteLine($"连接失败: {ex.Message}");
throw;
}
}
public void Disconnect()
{
_master?.Close();
_serialPort?.Close();
}
}
2. 数据读取操作
public ushort[] ReadHoldingRegisters(byte slaveId, ushort startAddr, ushort count)
{
try
{
return _master.ReadHoldingRegisters(slaveId, startAddr, count);
}
catch (ModbusException ex)
{
Console.WriteLine($"Modbus错误: {ex.ErrorCode}");
return null;
}
catch (IOException ex)
{
Console.WriteLine($"通信异常: {ex.Message}");
return null;
}
}
// 示例调用
var data = master.ReadHoldingRegisters(1, 0, 10); // 从站1读取保持寄存器0-9
3. 数据写入操作
public void WriteSingleRegister(byte slaveId, ushort address, ushort value)
{
_master.WriteSingleRegister(slaveId, address, value);
}
public void WriteMultipleCoils(byte slaveId, ushort startAddr, bool[] values)
{
_master.WriteMultipleCoils(slaveId, startAddr, values);
}
三、关键功能实现
1. CRC16校验（Modbus标准）
public static class Crc16
{
public static byte[] Compute(byte[] data)
{
ushort crc = 0xFFFF;
foreach (byte b in data)
{
crc ^= (ushort)b;
for (int i = 0; i < 8; i++)
{
if ((crc & 0x0001) != 0)
{
crc >>= 1;
crc ^= 0xA001;
}
else
{
crc >>= 1;
}
}
}
return new[] {
(byte)crc, (byte)(crc >> 8) };
}
public static bool Validate(byte[] dataWithCrc)
{
if (dataWithCrc.Length < 2) return false;
byte[] data = dataWithCrc.Take(dataWithCrc.Length - 2).ToArray();
byte[] crc = Compute(data);
return crc[0] == dataWithCrc[dataWithCrc.Length - 2]
&& crc[1] == dataWithCrc[dataWithCrc.Length - 1];
}
}
2. 帧间延迟计算
private int CalculateInterFrameDelay()
{
int charBits = 1 + _serialPort.DataBits +
(_serialPort.StopBits == StopBits.One ? 1 : 2) +
(_serialPort.Parity == Parity.None ? 0 : 1);
return (int)(3500.0 * charBits / _serialPort.BaudRate); // 3.5字符时间
}
四、错误处理与调试
1. 异常处理策略
try
{
var data = ReadHoldingRegisters(1, 0, 10);
if (data == null) throw new InvalidOperationException("读取失败");
}
catch (TimeoutException)
{
Console.WriteLine("通信超时，请检查设备状态");
Reconnect();
}
catch (InvalidOperationException ex)
{
Console.WriteLine($"操作失败: {ex.Message}");
}
2. 自动重连机制
private void Reconnect()
{
Disconnect();
Thread.Sleep(1000);
Connect(_config.PortName, _config.BaudRate);
}
五、性能优化
1批量操作优化
// 批量读取多个寄存器区域
public Dictionary<ushort, ushort[]> BatchRead(
params (byte SlaveId, ushort StartAddr, ushort Count)[] requests)
{
var results = new Dictionary<ushort, ushort[]>();
Parallel.ForEach(requests, request =>
{
var data = ReadHoldingRegisters(request.SlaveId, request.StartAddr, request.Count);
lock (results) results[request.SlaveId] = data;
});
return results;
}
2异步通信实现
public async Task<ushort[]> ReadAsync(byte slaveId, ushort startAddr, ushort count)
{
return await Task.Run(() => ReadHoldingRegisters(slaveId, startAddr, count));
}
参考代码 C#利用modbus rtu模式与下位机通讯 www.youwenfan.com/contentalg/112701.html
六、完整项目结构
ModbusRTUDemo/
├── src/
│ ├── ModbusMaster/ // 主站核心逻辑
│ ├── SerialPortConfig.cs // 串口配置管理
│ └── ProtocolHandler.cs // 协议解析器
├── tests/
│ ├── ModbusTests.cs // 单元测试
│ └── StressTests.cs // 压力测试
└── docs/
└── 开发指南.md
七、调试与测试工具
虚拟串口工具
使用VSPD创建虚拟串口对（如COM3<->COM4），方便调试
Wireshark抓包分析
过滤
Modbus RTU协议，观察完整的请求/响应帧结构Modbus从站模拟
使用Modbus Slave工具创建测试从站设备
八、扩展应用场景
1.多从站管理
public class ModbusNetwork
{
private Dictionary<byte, ModbusRtuMaster> _slaves = new();
public void AddSlave(byte address, string portName)
{
var master = new ModbusRtuMaster();
master.Connect(portName);
_slaves[address] = master;
}
}
2.数据缓存机制
public class DataCache
{
private Dictionary<ushort, (DateTime Timestamp, ushort Value)[]> _cache = new();
public void UpdateCache(ushort[] data, ushort startAddr)
{
_cache[startAddr] = data.Select((v, i) =>
(DateTime.Now, v)).ToArray();
}
}
九、最佳实践建议
参数配置规范
波特率：9600/19200/115200（根据设备手册选择）
数据格式：8N1（默认配置）
超时时间：读操作1000ms，写操作500ms
安全防护措施
添加设备认证机制
实现数据加密传输
设置访问权限控制
