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private void button1_Click(object sender, EventArgs e)
        {

            this.backgroundWorker1.RunWorkerAsync();
        }

        private void scan()
        {
            Ping pingSender = new Ping();
            PingOptions options = new PingOptions();

            options.DontFragment = true;

            this.ping_progressbar1.Maximum = 255;
            this.ping_progressbar1.Step = 1;


            for (int id = 0; id < 255; id++)
            {
                string aktip;
                string netz;
                string data;
                string idstr;
                int tout = 120;

                
                netz = "192.168.178.";
                aktip = netz + id.ToString();
                data = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa";  

                
                this.ping_progressbar1.Value = id;
                
                //ping senden
                byte[] buffer = Encoding.ASCII.GetBytes(data);
                PingReply reply = pingSender.Send(aktip, tout, buffer, options);

                
                if (reply.Status == IPStatus.Success)
                {
                    this.listBox1.Items.Add(aktip);
                }
            }                       
        }

        private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
        {
            scan();
        }