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客户端和服务器之间的通信，服务器要时刻知道客户端的网络连接状态..

  #region ++++++++++++++++++++客户端的感觉系统
        //启动记时器
        public void BeginTheTimer()
        {
            //th_UserLogin();
            object myobject = (object)7;    //这里只是要一个object类型数据，用它做为下面Timer的参数之一，其它没有什么意思
            //暂时设定为1秒钟启动一次！
            System.Threading.Timer t = new System.Threading.Timer(new System.Threading.TimerCallback(testTheNet), myobject, 1000, 1000);
        }

        //启动监视"已登录用户通信情况"的线程
        public void testTheNet(object myobject) 
        {
            //UserPassport up=new UserPassport();
            Thread sendMyPulseThPro = new Thread(new ThreadStart(delegateSendMyPulse));
            sendMyPulseThPro.Start();
        } 
       
        /// <summary>
        /// 每隔1秒就是要来做这些事情的
        /// </summary>
        public void delegateSendMyPulse()
        {
            loginServer lser = new loginServer();
            Login l = new Login();
            l.Id = lser.MyLogin.Id;
            l.ClientTypeVersion = version;
            l.RequestType = 3;          //3是确认联接正常的一个信号（让服务知道它与服务器的联接是正常的）
            loginServer lserver = new loginServer();           
            Thread thSendDat2 = new Thread(new ParameterizedThreadStart(lserver.delgSendDataMethod));//启动一个新线程去发送数据
            thSendDat2.Start(l);
            thSendDat2.IsBackground = true;
            longinserver.MyLostTime += 1;   //标记我已经发送出去一次数据了
            if(longinserver.MyLostTime>=3)    //如果外发了3次请求暗号后仍不见服务器的回应，则认为客户端已经与服务器断开联系了
            {
                //停止Timer
                //告诉用户：“你已经与服务器失去联系了…………”
                longinserver.Controls["txtShowMsg"].Text = "You have lost the connect!";
            }
        }
        #endregion +++++++++++++++++++++客户端的感觉系统

服务器端代码如下：

  #region +++++++++++++++++++++++服务器的感觉系统
        //启动记时器
        public void LoadTheTimer()
        {
            object o=(object)loginedCount++;
            UserPassport up = new UserPassport();

            //暂时设定为1秒钟启动一次！
            System.Threading.Timer t = new System.Threading.Timer(new System.Threading.TimerCallback(watchTheLoginUser), o, 1000, 1000);           
                   }

        //启动监视"已登录用户通信情况"的线程
        public void watchTheLoginUser(object o)
        {
            //UserPassport up=new UserPassport();
            Thread checktheloginuser = new Thread(new ThreadStart(iAmAWatcher));
            checktheloginuser.Start();
        }

        //真正做事的工人:这个工人的使命是每隔1秒钟后就查看一下登记薄registry里面有谁没有定时来向服务器报到了，如果出现谁三次检查都没有签到则除之名
        public void iAmAWatcher()
        {
            this.txtLogin.Text += "@+";
            int index = 0;
            for (index = 0; index < loginedCount; index++)
            {
                if (myRegistry[index].alive==false&&registry[index].studentID!="")
                {
                    lock(this)
                    {
                        myRegistry[index].no_check_in_count += 1;           //坏（未到）记录增加一次                   
                        if (myRegistry[index].no_check_in_count >= 3)
                        {
                            //this.lblShowMsg.Text = "the student" + registry[index].studentID.ToString() + "is diaoxianle!";
                            this.txtLogin.Text += "88";
                            //标记该人已经与服务器失去连接了，因为他有连续3次的未到记录存在
                            registry[index].studentID = "";
                            registry[index].StudentName = "";
                            registry[index].StudentIP = "";
                            registry[index].status = 2;      //掉线
                           
                        }
                    }
                }

            }
        }//定时检查在线人目前状态
        #endregion +++++++++++++++++++服务器的感觉系统

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