监控线程的问题！

我想实现一个简单的线程监控！就是客户端登陆的时候，我吧他的登陆时间保存的数据库，他离开的时候（直接关闭网页或者断电了）获得它离开的时间保存到数据库！我不知道该怎么写，就到网上看了下，科室捣鼓了半天没搞明白！到底是怎么监控，代码写了一点点不知道对不对，而且是在写不下去了，希望各位大侠帮帮忙给修改或者完善下代码！
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading;
using
using
using

using JH.Game.ServiceLibrary.Model;
using JH.Game.ServiceLibrary.Bll;

using FluorineFx.Data;
using FluorineFx;
using FluorineFx.AMF3;

namespace JH.Game.ServiceLibrary.RemotingService
{
    [RemotingService]
   public class listener
    {

        public listener()
        {
            
        }
        //IP地址
        private IPAddress ip;

        //端口
        private int port;

        //监听器
        private TcpListener Tcls = null;

        //监听线程
        private Thread th;

         //启动线程
        private void Start()
        {
            th = new Thread(new ThreadStart(Func));
            th.IsBackground=true;
            th.Start();            
        }

        //停止线程        
        private void Stop()
        {
            th.Abort();
            if (Tcls != null)
            {
                Tcls.Stop();
                Tcls = null;
            }
        }
        private void Func()
        {
            Tcls = new TcpListener(ip,port);
            Tcls.Start();
            while (true)
            {
                if (Tcls.Pending())
                {
                    TcpClient tc = Tcls.AcceptTcpClient();
                  
                    Client cl = new Client(tc, th);
                    th.Start(cl);
                }
                else
                {
                    Thread.Sleep(300);
                }
            }
        }
系统为B/s结构，谢谢大家了！