用VB.NET写一个关于图莫斯CAN通讯的示例，不能使用TPCAN库

以下是一个使用VB.NET与图莫斯CAN通讯的示例，该示例不使用TPCAN库，而是使用了Windows API函数来实现CAN数据的读写操作。请注意，该示例仅供参考，具体实现需要根据自己的实际情况进行调整。

Imports System.Runtime.InteropServices

Public Class Form1
    Const WM_USER = &H400
    Const WM_CAN_MESSAGE = WM_USER + 1

    Private m_hCan As IntPtr
    Private m_hWnd As IntPtr

    Private Structure CanMessage
        Public id As UInt32
        Public flags As UInt32
        Public len As Byte
        <MarshalAs(UnmanagedType.ByValArray, SizeConst:=8)> Public data() As Byte
    End Structure

    Private Declare Function OpenCAN Lib "WPCAN.dll" (ByVal port As Integer, ByVal baudrate As Integer) As IntPtr
    Private Declare Function CloseCAN Lib "WPCAN.dll" (ByVal handle As IntPtr) As Integer
    Private Declare Function WriteCAN Lib "WPCAN.dll" (ByVal handle As IntPtr, ByRef msg As CanMessage) As Integer
    Private Declare Function ReadCAN Lib "WPCAN.dll" (ByVal handle As IntPtr, ByRef msg As CanMessage) As Integer
    Private Declare Function SetReceiveCallback Lib "WPCAN.dll" (ByVal handle As IntPtr, ByVal hWnd As IntPtr, ByVal msg As Integer) As Integer

    Protected Overrides Sub WndProc(ByRef m As Message)
        If m.Msg = WM_CAN_MESSAGE Then
            Dim msg As CanMessage
            Dim len As Integer = Marshal.SizeOf(msg)
            Dim lpData As IntPtr = Marshal.AllocHGlobal(len)

            Try
                Marshal.Copy(m.LParam, lpData, 0, len)
                msg = Marshal.PtrToStructure(lpData, GetType(CanMessage))

                '在这里处理CAN数据'
            Finally
                Marshal.FreeHGlobal(lpData)
            End Try
        End If

        MyBase.WndProc(m)
    End Sub

    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        m_hCan = OpenCAN(0, 500000) '打开CAN通讯端口'
        m_hWnd = Me.Handle
        SetReceiveCallback(m_hCan, m_hWnd, WM_CAN_MESSAGE) '设置接收回调函数'
    End Sub

    Private Sub Form1_FormClosing(sender As Object, e As FormClosingEventArgs) Handles MyBase.FormClosing
        CloseCAN(m_hCan) '关闭CAN通讯端口'
    End Sub

    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
        Dim msg As CanMessage
        msg.id = &H123
        msg.flags = 0
        msg.len = 8
        ReDim msg.data(msg.len - 1)
        msg.data(0) = 1
        msg.data(1) = 2
        msg.data(2) = 3
        msg.data(3) = 4
        msg.data(4) = 5
        msg.data(5) = 6
        msg.data(6) = 7
        msg.data(7) = 8

        WriteCAN(m_hCan, msg) '发送CAN数据帧'
    End Sub
End Class

在示例中，使用了Windows API函数OpenCAN、CloseCAN、WriteCAN、ReadCAN和SetReceiveCallback来实现CAN数据的读写操作和接收回调函数的设置。在窗体加载时，调用OpenCAN函数打开CAN通讯端口，同时设置接收回调函数以便在接收到CAN数据时进行处理。在窗体关闭时，调用CloseCAN函数关闭CAN通讯端口。在发送CAN数据时，构造一个CanMessage结构体，并调用WriteCAN函数发送数据帧。

请注意，在实际应用中，需要根据自己的实际情况设置CAN总线参数和处理CAN数据的方法。