// start frmDisplay.cs
    public partial class frmDisplay : Form
    {

        private TaktServer taktsv = new TaktServer( "192.168.0.220", 14124 );
        private int time_count = 0;

        public frmDisplay()
        {
            InitializeComponent();
            this.FormClosing += TidyUp_Server;
            //StartTimer();
        }

        public void StartTimer()
        {
            timer.Start();
        }

        public void StopTimer()
        {
            timer.Stop();
        }

    // Extra unrelated code removed.

    }
// end frmDisplay.cs

// start TaktServer.cs
    public class TaktServer
    {
        // unrelated code removed
        // string command is a command received from the client.
                string command = clientEncoder.GetString(msg, 0, bytesRead);

                switch( command )
                {

                    case "fail":
                        MessageBox.Show( "fail!" );
                        Environment.Exit(100);
                    break;

                    case "start":
                        MessageBox.Show("start");
            // How would I start frmDisplay's timer here?
                        byte[] message = encoder.GetBytes("fanks");
                        clientStream.Write(message, 0, message.Length);
                        clientStream.Flush();
                    break;

                    case "stop":
                        MessageBox.Show("stop");
                    break;

                }

         // unrelated code removed
    }
// end TaktServer.cs