C#不使用第三方库开发一个Modbus tcp 实时通讯寄存器

以下是一个使用C#编写的Modbus TCP客户端示例代码，不使用第三方库。该示例代码使用了Socket类实现TCP连接和通信：

using System;
using System.Net.Sockets;

class ModbusTcpClient
{
    private Socket _socket;

    public ModbusTcpClient(string ip, int port)
    {
        _socket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
        _socket.Connect(ip, port);
    }

    public ushort[] ReadHoldingRegisters(byte slaveId, ushort startAddress, ushort count)
    {
        byte[] request = BuildModbusRequest(slaveId, 3, startAddress, count);
        _socket.Send(request);
        byte[] response = new byte[8 + count * 2];
        _socket.Receive(response);
        ushort[] values = new ushort[count];
        for (int i = 0; i < count; i++)
        {
            values[i] = (ushort)(response[9 + i * 2] << 8 | response[10 + i * 2]);
        }
        return values;
    }

    public void WriteSingleRegister(byte slaveId, ushort address, ushort value)
    {
        byte[] request = BuildModbusRequest(slaveId, 6, address, value);
        _socket.Send(request);
        byte[] response = new byte[8];
        _socket.Receive(response);
    }

    private byte[] BuildModbusRequest(byte slaveId, byte functionCode, ushort address, ushort value)
    {
        byte[] request = new byte[12];
        request[0] = slaveId;
        request[1] = functionCode;
        request[2] = (byte)(address >> 8);
        request[3] = (byte)(address & 0xFF);
        request[4] = (byte)(value >> 8);
        request[5] = (byte)(value & 0xFF);
        ushort crc = CalculateCrc(request, 6);
        request[6] = (byte)(crc & 0xFF);
        request[7] = (byte)(crc >> 8);
        return request;
    }

    private ushort CalculateCrc(byte[] buffer, int length)
    {
        ushort crc = 0xFFFF;
        for (int i = 0; i < length; i++)
        {
            crc ^= buffer[i];
            for (int j = 0; j < 8; j++)
            {
                if ((crc & 0x0001) != 0)
                {
                    crc >>= 1;
                    crc ^= 0xA001;
                }
                else
                {
                    crc >>= 1;
                }
            }
        }
        return crc;
    }
}

在使用该示例代码时，需要先创建一个ModbusTcpClient对象，并传入Modbus TCP服务器的IP地址和端口号。例如：

ModbusTcpClient client = new ModbusTcpClient("192.168.1.10", 502);

然后，可以使用ReadHoldingRegisters方法读取寄存器值，或使用WriteSingleRegister方法写入寄存器值。例如：

ushort[] values = client.ReadHoldingRegisters(1, 0, 10); // 读取从机1的寄存器0~9的值
client.WriteSingleRegister(1, 0, 1234); // 将从机1的寄存器0的值设置为1234

注意，该示例代码仅实现了读取保持寄存器（Function Code 03）和写单个寄存器（Function Code 06）的功能。如果需要实现其他功能码的功能，需要根据Modbus协议规范进行相应的实现。