Transfor file by COM Port

Sub TransforFiles(ByVal sendFile As String)
        Dim bys As Byte() = My.Computer.FileSystem.ReadAllBytes(sendFile)
        Dim cx = bys.Length
        Dim T1 As Integer = 0
        Dim Clength As Integer
        If cx > 4096 Then
            Dim count As Integer = cx \ 4096
            Do While T1 < count + 1
                Clength = cx - (T1 * 4096)
                If Clength > 4096 Then Clength = 4096
                SerialPort1.Write(bys, T1 * 4096, Clength)
                System.Threading.Thread.Sleep(500)
                TextBox1.AppendText(T1.ToString + "Send No." + Clength.ToString + vbNewLine)
                T1 = T1 + 1
            Loop
        Else
            SerialPort1.Write(bys, 0, cx)
            TextBox1.AppendText("Send " + cx.ToString)
        End If

    End Sub