C# 上位机与plc基于modbus tcp通讯程序

下面是一个 C# 上位机与 PLC 基于 Modbus TCP 通讯的程序示例：

using System;
using System.Net.Sockets;
using System.Threading;

namespace ModbusTcp
{
    class Program
    {
        static void Main(string[] args)
        {
            // PLC IP地址和端口号
            string ip = "192.168.1.100";
            int port = 502;

            // 创建TCP连接
            TcpClient client = new TcpClient(ip, port);

            // 创建Modbus协议对象
            ModbusTcpProtocol protocol = new ModbusTcpProtocol(client);

            // 连接到PLC
            protocol.Connect();

            // 读取PLC寄存器值
            ushort[] values = protocol.ReadHoldingRegisters(0, 10);

            // 输出读取到的值
            for (int i = 0; i < values.Length; i++)
            {
                Console.WriteLine("Register {0}: {1}", i, values[i]);
            }

            // 关闭连接
            protocol.Disconnect();
            client.Close();
        }
    }

    // Modbus TCP 协议类
    class ModbusTcpProtocol
    {
        TcpClient client; // TCP客户端对象
        NetworkStream stream; // 网络流对象

        // 构造函数
        public ModbusTcpProtocol(TcpClient client)
        {
            this.client = client;
            this.stream = client.GetStream();
        }

        // 连接到PLC
        public void Connect()
        {
            // 发送连接请求
            byte[] connectRequest = new byte[] { 0x00, 0x00, 0x00, 0x00, 0x00, 0x06, 0x01, 0x03, 0x00, 0x00, 0x00, 0x0A };
            stream.Write(connectRequest, 0, connectRequest.Length);

            // 读取响应
            byte[] response = new byte[12];
            stream.Read(response, 0, response.Length);

            // 检查响应是否为连接确认
            if (response[7] != 0x03 || response[8] != 0x00 || response[9] != 0x00 || response[10] != 0x00 || response[11] != 0x0A)
            {
                throw new Exception("Failed to connect to PLC");
            }
        }

        // 关闭连接
        public void Disconnect()
        {
            // 发送断开连接请求
            byte[] disconnectRequest = new byte[] { 0x00, 0x00, 0x00, 0x00, 0x00, 0x06, 0x01, 0x03, 0x00, 0x00, 0x00, 0x0A };
            stream.Write(disconnectRequest, 0, disconnectRequest.Length);
        }

        // 读取保持寄存器
        public ushort[] ReadHoldingRegisters(ushort startAddress, ushort numRegisters)
        {
            // 发送读取请求
            byte[] request = new byte[] { 0x00, 0x00, 0x00, 0x00, 0x00, 0x06, 0x01, 0x03, (byte)(startAddress >> 8), (byte)startAddress, (byte)(numRegisters >> 8), (byte)numRegisters };
            stream.Write(request, 0, request.Length);

            // 读取响应
            byte[] response = new byte[9 + numRegisters * 2];
            stream.Read(response, 0, response.Length);

            // 解析响应
            ushort[] values = new ushort[numRegisters];
            for (int i = 0; i < numRegisters; i++)
            {
                values[i] = (ushort)(response[9 + i * 2] << 8 | response[10 + i * 2]);
            }
            return values;
        }
    }
}

需要注意的是，这只是一个简单的示例程序，实际应用中需要根据具体的设备和通讯方式进行修改和调试。