在VBNET中如何实现MODBUS-RTU通讯协议，并且处理异常？请提供一个简单的示例代码。

在VBNET中实现MODBUS-RTU通讯协议涉及到一系列的步骤，包括串口初始化、数据封装与解析、读写操作以及异常处理。为了帮助你更好地掌握这一技能，建议参考《VBNET实现MODBUS-RTU通信协议示例程序解析》这一资料。下面我将为你展示一个简单的示例代码，用于在VBNET环境下实现MODBUS-RTU通讯协议，并处理可能出现的异常：

参考资源链接：[VBNET实现MODBUS-RTU通信协议示例程序解析](https://wenku.csdn.net/doc/70n6hnqf4j?spm=1055.2569.3001.10343)

Imports System.IO.Ports
Imports System.Text

Public Class ModbusRTUCommunication
    Private sp As New SerialPort()

    ' 初始化串口参数
    Private Sub SetupSerialPort(portName As String, baudRate As Integer)
        sp.PortName = portName
        sp.BaudRate = baudRate
        sp.Parity = Parity.None
        sp.DataBits = 8
        sp.StopBits = StopBits.One
        sp.ReadTimeout = 500
        sp.WriteTimeout = 500
    End Sub

    ' 构造MODBUS RTU请求帧
    Private Function CreateRequestFrame(functionCode As Byte, address As UShort, value As UShort) As Byte()
        Dim dataBytes() As Byte = {CByte(address >> 8), CByte(address Mod &HFF), functionCode, CByte(value >> 8), CByte(value Mod &HFF)}
        Dim crc As UShort = CalculateCRC(dataBytes)
        Return {dataBytes(0), dataBytes(1), dataBytes(2), CByte(crc >> 8), CByte(crc Mod &HFF)}
    End Function

    ' 计算CRC校验码
    Private Function CalculateCRC(data() As Byte) As UShort
        Dim crc As UShort = &HFFFF
        For Each b As Byte In data
            crc = (crc >> 8) Xor crcTable((crc Xor b) And &HFF)
        Next
        Return crc
    End Function

    ' CRC校验表
    Private Shared crcTable As UShort() = {&H0000, &HC0C1, &HC181, &H0140, ... }

    ' 发送请求并接收响应
    Public Function SendModbusRequest(functionCode As Byte, address As UShort, value As UShort) As Byte()
        Try
            Dim requestFrame() As Byte = CreateRequestFrame(functionCode, address, value)
            sp.Open()
            sp.Write(requestFrame, 0, requestFrame.Length)
            Dim response As Byte() = New Byte(19) {}
            sp.Read(response, 0, response.Length)
            sp.Close()
            ' 校验响应帧的CRC
            Dim receivedCRC As UShort = CType(((response(2) << 8) Or response(3)), UShort)
            If receivedCRC <> CalculateCRC(response.Take(2).Concat(response.Skip(4)).ToArray()) Then
                Throw New Exception(

参考资源链接：[VBNET实现MODBUS-RTU通信协议示例程序解析](https://wenku.csdn.net/doc/70n6hnqf4j?spm=1055.2569.3001.10343)