private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
        {
            TcpListener tcp = new TcpListener(System.Net.IPAddress.Any, port);
            tcp.Start();
            bw1.ReportProgress(0, "Local end point: " + tcp.Server.LocalEndPoint.ToString());
            bw1.ReportProgress(0, "Listening on port " + port);
            while (true)
            {
                try
                {
                    TcpClient t = tcp.AcceptTcpClient();
                    if (t.Connected)
                    {
                        bw1.ReportProgress(0, "Accepted connection from " + t.Client.RemoteEndPoint.ToString());
                        DataStream ds = new DataStream(t.GetStream());
                        String user = ds.readString();
                        String pass = ds.readString();
                        bw1.ReportProgress(0, "User: " + user + " : ********");
                        Boolean auth = isAuthenticated(user, pass);
                        bw1.ReportProgress(0, "User " + (auth ? "accepted" : "unauthorized"));
                        if (auth)
                            ds.writeString("OK");
                        else
                            ds.writeString("NOTOK");
                        int c = getClientIndex();
                        if (c < 0) {
                            bw1.ReportProgress(0, "Max clients connected");
                            ds.writeString("Max clients connected");
                            t.Close();
                            continue;
                        }
                        clients[c] = new Client(this, bw1, t, user);
                    }
                }
                catch (Exception)
                {
                    //bw1.ReportProgress(0, ex.Message);
                }
                System.Threading.Thread.Sleep(50);
            }
        }