public Hashtable threadTable = new Hashtable();
        public Hashtable clientTable = new Hashtable();

            this.tcpListener = new TcpListener(IPAddress.Any, 3000);
            this.listenThread = new Thread(new ThreadStart(ListenForClients));
            listenThread.Name = "WaitForClient";
            this.listenThread.Start();
            threadTable.Add(listenThread.Name, listenThread);

        private void frmMain_FormClosing(object sender, FormClosingEventArgs e) _
          {
            if (clientTable.Count > 0) {
                foreach (DictionaryEntry threadObject in clientTable) {
                    try {
                        Thread exitThread = (Thread)threadObject.Value;
                        if (exitThread != null)
                            exitThread.Abort();
                    } catch {
                        MessageBox.Show("Fehler beim beenden von Threads", _
                          "Threadfehler", MessageBoxButtons.OK, _
                          MessageBoxIcon.Error);
                    }
                }
            }
 
            if (threadTable.Count > 0) {
                foreach (DictionaryEntry threadObject in threadTable) {
                    try {
                        Thread exitThread = (Thread)threadObject.Value;
                        if (exitThread != null)
                            exitThread.Abort();
                    } catch {
                        MessageBox.Show("Fehler beim beenden von Threads", _
                          "Threadfehler", MessageBoxButtons.OK, _
                          MessageBoxIcon.Error);
                    }
                }
            }
        }
    }