Imports System
Imports System.IO.Ports

Public Class Form1

    Private Sub Form1_Load(ByVal sender As System.Object,ByVal e As System.EventArgs) Handles MyBase.Load
        '获取计算机有效串口
        Dim ports As String() = SerialPort.GetPortNames() '必须用命名空间，用SerialPort,获取计算机的有效串口
        Dim port As String
        For Each port In ports
            portnameBox.Items.Add(port) '向comboBox中添加项
        Next port
        '初始化界面
        baudrateBox.SelectedIndex() = 2
        portnameBox.SelectedIndex() = 0
        Serial_Port1() '初始化串口
        Label3.Text = SerialPort1.IsOpen
        statuslabel.Text = "串口未连接"
        statuslabel.ForeColor = Color.Red
        sendBox.Text = "123"
        ' baudrateBox.Text = baudrateBox.Items(0) 注释和不注释的地方可以替换
        'portnameBox.Text = portnameBox.Items(0)
    End Sub

    Private Sub Serial_Port1() '设置串口参数
        SerialPort1.BaudRate = Val(baudrateBox.Text) '波特率
        SerialPort1.PortName = portnameBox.Text '串口名称
        SerialPort1.DataBits = 8 '数据位
        SerialPort1.StopBits = IO.Ports.StopBits.One '停止位
        SerialPort1.Parity = IO.Ports.Parity.None '校验位
    End Sub

    '关闭串口连接
    Private Sub closebtn_Click(ByVal sender As System.Object,ByVal e As System.EventArgs) Handles closebtn.Click
        Try
            SerialPort1.Close() '关闭串口
            Label3.Text = SerialPort1.IsOpen
            If SerialPort1.IsOpen = False Then
                statuslabel.Text = "串口未连接"
                statuslabel.ForeColor = Color.Red
                receiveBox.Text = ""
                receivebytes.Text = ""
            End If
        Catch ex As Exception
            MessageBox.Show(ex.Message)
        End Try
    End Sub

    '打开串口连接
    Private Sub openbtn_Click(ByVal sender As System.Object,ByVal e As System.EventArgs) Handles openbtn.Click
        Try
            SerialPort1.Open() '打开串口
            Label3.Text = SerialPort1.IsOpen
            If SerialPort1.IsOpen = True Then
                statuslabel.Text = "串口已连接"
                statuslabel.ForeColor = Color.Green
            End If
        Catch ex As Exception
            MessageBox.Show(ex.Message)
        End Try
    End Sub


    '发送数据
    Private Sub Button1_Click(ByVal sender As System.Object,ByVal e As System.EventArgs) Handles Button1.Click
        Try
            SerialPort1.Write(sendBox.Text)
        Catch ex As Exception
            MessageBox.Show(ex.Message)
        End Try

    End Sub

    '触发接收事件
    Public Sub Sp_DataReceived(ByVal sender As Object,ByVal e As System.IO.Ports.SerialDataReceivedEventArgs) Handles SerialPort1.DataReceived
        Me.Invoke(New EventHandler(AddressOf Sp_Receiving)) '调用接收数据函数
    End Sub

    '接收数据
    Private Sub Sp_Receiving(ByVal sender As Object,ByVal e As EventArgs)
        Dim strIncoming As String
        Try
            receivebytes.Text = Str(Val(receivebytes.Text) + SerialPort1.BytesToRead)
            If SerialPort1.BytesToRead > 0 Then
                Threading.Thread.Sleep(100) '添加的延时
                strIncoming = SerialPort1.ReadExisting.ToString '读取缓冲区中的数据
                SerialPort1.DiscardInBuffer()
                receiveBox.Text = strIncoming
            End If
        Catch ex As Exception
            MessageBox.Show(ex.Message)
        End Try
    End Sub
End Class