how to receive Text from sms receiver

Dim readBuffer As String
    Private Sub btnConnect_Click(sender As System.Object, e As System.EventArgs) Handles btnConnect.Click

        With SerialPort1

            .ParityReplace = &H3B
            .PortName = "COM1" 'your com serial port
            .BaudRate = 115200
            .Parity = IO.Ports.Parity.None
            .DataBits = 8
            .StopBits = IO.Ports.StopBits.One
            .Handshake = IO.Ports.Handshake.None
            .RtsEnable = False
            .ReceivedBytesThreshold = 1
            .NewLine = vbCr
            .ReadTimeout = 10000

        End With

        Try
            SerialPort1.Open()
        Catch ex As Exception
            MsgBox("Error Open: " & ex.Message)
        End Try

        btnConnect.Enabled = Not SerialPort1.IsOpen
        btnDisconnect.Enabled = SerialPort1.IsOpen
        btnATCommandSend.Enabled = SerialPort1.IsOpen
    End Sub

    Private Sub btnDisconnect_Click(sender As System.Object, e As System.EventArgs) Handles btnDisconnect.Click
        If SerialPort1.IsOpen = True Then
            SerialPort1.DiscardInBuffer()
            SerialPort1.Close()
        End If
        btnConnect.Enabled = Not SerialPort1.IsOpen
        btnDisconnect.Enabled = SerialPort1.IsOpen
        btnATCommandSend.Enabled = SerialPort1.IsOpen
    End Sub

    Private Sub SerialPort1_DataReceived(ByVal sender As System.Object, _
                                        ByVal e As System.IO.Ports.SerialDataReceivedEventArgs) _
                                        Handles SerialPort1.DataReceived

        Try
            readBuffer = SerialPort1.ReadLine()
            Me.Invoke(New EventHandler(AddressOf DoUpdate))

        Catch ex As Exception
            MsgBox("read " & ex.Message)
        End Try

    End Sub

    Private Sub DoUpdate(ByVal sender As Object, ByVal e As System.EventArgs)
        TextBox1.Text = readBuffer
    End Sub

    Private Sub btnATCommandSend_Click(sender As System.Object, e As System.EventArgs) Handles btnATCommandSend.Click
        'AT For read message by index= AT+CMGR=1 'sms index
        'PLEASE REFER ATCOMMAND for more command

        SerialPort1.WriteLine(TextBox2.Text)
    End Sub