private void SendNC(object sender, EventArgs e)
        {
                port.Handshake = Handshake.XOnXOff;

            foreach (var item in listBox1.SelectedItems)
                {
                string FileName = item.ToString();
                richTextBox1.AppendText(Environment.NewLine + "Invio in corso..." + Environment.NewLine + FileName);
                port.Write(Environment.NewLine + File.OpenText(FileName).ReadToEnd());
                richTextBox1.AppendText(Environment.NewLine + "File inviato con successo!" + Environment.NewLine);
                port.Handshake = Handshake.None;
                }
                port.Close();
                richTextBox1.AppendText("Invio Terminato!\n");
        }