C# C/S 客户端不能正确接收服务器发来的第二次数据

Question

在登陆过程中客户端新建了个线程来和服务器会话
 private void 登陆_Load(object sender, EventArgs e)
        {
            contactWithServer = new ContactWithServer(this, user);
            Thread clientcontactserverThread = new Thread(new ThreadStart(contactWithServer.contact));
            clientcontactserverThread.Start();           
        }
客户端接收程序
  public void contact()
     {
        //receiveIpep = new IPEndPoint(IPAddress.Parse(serverIP), 8888);
        ////sendIpep = new IPEndPoint(IPAddress.Parse(serverIP), 6666);       //服务器端接收端口
        //udpReceiveClient = new UdpClient(receiveIpep);
        receiveIpep = null;       
        try
        {
            udpReceiveClient = new UdpClient(8888);
            while (true)
            {
                MessageBox.Show("where"); 
                byte[] data = udpReceiveClient.Receive(ref receiveIpep);
                if (data.Length < 20)                       //只有命令
                    commandStr = Encoding.ASCII.GetString(data);
                else                                       //既有命令又有数据
                {
                    int i = 0;
                    ///取出命令
                    for (i = 0; i < leng; i++)
                    {
                        if (Convert.ToInt32(data[i]) == 0)    //寻找请求中的有效字符的最终位置
                            break;
                    }
                    byte[] cmdbyte = new byte[i];
                    for (int k = 0; k < i; k++)
                    {
                        cmdbyte[k] = data[k];
                    }
                    commandStr = Encoding.ASCII.GetString(cmdbyte);                    
                }
                MessageBox.Show(commandStr, "来自服务器的命令！");
                switch (commandStr)
                {
                    case "LoginSuccess":
                        {
                            登陆.LoginFormDelegate closeDelegate = new 登陆.LoginFormDelegate(loginFormAction);
                            loginForm.Invoke(closeDelegate, new String[] { "close" });
                            loginForm.isFirst = false;         //客户端已登陆成功，下次发给服务器的消息从另一端口发出
                            frm = new 申请及扫描(user, this);
                            frm.ShowDialog();
                        }
                        break;
                    case "LoginFail":
                        {
                            MessageBox.Show("用户名或者密码错误");
                            登陆.LoginFormDelegate clearDelegate = new 登陆.LoginFormDelegate(loginFormAction);
                            loginForm.Invoke(clearDelegate, new String[] { "clear" });
                        }
                        break;
                    case "ReFreshData":
                        buff = new byte[data.Length - leng];
                        for (int j = 0; j < data.Length - leng; j++)
                            buff[j] = data[leng + j];
                        memStream = new MemoryStream(buff);
                        memStream.Seek(0, SeekOrigin.Begin);
                        memStream.Flush();
                        DataTable dt = new DataTable();
                        dt = (DataTable)formatter.Deserialize(memStream);
                        memStream.Close();
                        MessageBox.Show("收到服务器的命令");
                        break;
                }
            }
        }
        catch (Exception ex)
        {
            MessageBox.Show(ex.Message);
        }
            
        }
客户端成功登陆后，程序执行到红字显示的内容后就去执行其它代码了，在此过程中服务器发过来的数据都不能接收，当客户端关闭后才能接收，不知道怎样修改

Answer 1

ShowDialog会阻塞，你用异步来做就行了。
与服务器的通讯放在一个独立的线程中，这样与UI相关的交互就不会阻塞了。

Answer 2

怎样实现异步呢？线程这块用的也不是很清楚，在客户端哪块new了一个新线程，就是打算用来和服务器沟通的独立线程

Answer 3

例子：http://download.csdn.net/detail/caozhy/5287998

Answer 4

 frm = new 申请及扫描(user, this);
                            frm.ShowDialog();
包含在 while (true)里面，你每一次都new一个窗体，当然了应该是判断窗体为空才new
if(frm==null){ frm = new 申请及扫描(user, this);}
 frm.ShowDialog();

Answer 5

在线程中，或循环体中的窗体，new时要特别注意判断是否为空，如果每次都new，那么每次都是新的窗体，后面想操作前面窗体的内容，就没办法操作了

Answer 6

已经加上了，还是去执行shoudialog时阻塞了，怎样解决呢

Answer 7

客户端在加载的时候创建了一个新线程，来接受服务器的消息：
contactWithServer = new ContactWithServer(this, user);
Thread clientcontactserverThread = new Thread(new ThreadStart(contactWithServer.ReceiveMsg));
            clientcontactserverThread.Start(); 
   public void ReceiveMsg()
        {
            while (true)
            {
                lock (this)
                {
                    // 调用接收回调函数
                    IAsyncResult iar = udpReceiveClient.BeginReceive(new AsyncCallback(ReceiveCallback), udpReceiveState);
                    receiveDone.WaitOne();
                    Thread.Sleep(100);
                }
            }
        }
        private void ReceiveCallback(IAsyncResult iar)
        {
            UdpState udpReceiveState = iar.AsyncState as UdpState;
            if (iar.IsCompleted)
            {
                data = udpReceiveState.udpClient.EndReceive(iar, ref udpReceiveState.ipEndPoint);
                if (data.Length < 20)                       //只有命令
                        commandStr = Encoding.ASCII.GetString(data);
                    else                                       //既有命令又有数据
                    {
                        int i = 0;
                        ///取出命令
                        for (i = 0; i < leng; i++)
                        {
                            if (Convert.ToInt32(data[i]) == 0)    //寻找请求中的有效字符的最终位置
                                break;
                        }
                        byte[] cmdbyte = new byte[i];
                        for (int k = 0; k < i; k++)
                        {
                            cmdbyte[k] = data[k];
                        }
                        commandStr = Encoding.ASCII.GetString(cmdbyte);                    
                    }
                    MessageBox.Show(commandStr, "来自服务器的命令！");
                    handleMsg(commandStr);                
                Thread.Sleep(100);
                receiveDone.Set();               
            }
        }
        private void handleMsg(string commandStr)
        {
            switch (commandStr)
            {
                case "LoginSuccess":
                    {
                        登陆.LoginFormDelegate closeDelegate = new 登陆.LoginFormDelegate(loginFormAction);
                        loginForm.Invoke(closeDelegate, new String[] { "close" });
                        loginForm.isFirst = false;         //客户端已登陆成功，下次发给服务器的消息从另一端口发出
                        frm = new 申请及扫描(user, this);
                        frm.ShowDialog();
                    }
                    break;
                case "LoginFail":
                    {
                        MessageBox.Show("用户名或者密码错误");
                        登陆.LoginFormDelegate clearDelegate = new 登陆.LoginFormDelegate(loginFormAction);
                        loginForm.Invoke(clearDelegate, new String[] { "clear" });
                    }
                    break;
                case "ReFreshData":
                    ///取出数据
                    buff = new byte[data.Length - leng];
                    for (int j = 0; j < data.Length - leng; j++)
                        buff[j] = data[leng + j];
                    memStream = new MemoryStream(buff);
                    memStream.Seek(0, SeekOrigin.Begin);
                    memStream.Flush();
                    DataTable dt = new DataTable();
                    dt = (DataTable)formatter.Deserialize(memStream);
                    memStream.Close();
                    MessageBox.Show("收到服务器的命令");
                    break;
            }
        }客户端这边登陆成功后会跳转到一个新窗体，接着从这个新窗体上给服务器发请求，服务器那边能收到消息，并且也给客户端这边回复了，客户端这边就是不能收到消息，只有关闭窗体时才能收到，自己简单的测试了下，是在frm.ShowDialog();这块停下了，没有接收服务器发来的消息，昨天有人说我的两边的通信方式是同步，改成异步通信后就行了，我就从网上找了个异步通信的例子，彻底照着改了，可是结果还是和昨天一样，不知道我改的哪有问题还是其它别的什么原因

Answer 8

比如在form1 中show form2， 
f2.ShowDialog() 后，除非有方法是写在f2窗体里，或者f2中可以调用你想要的方法，否则，在f2关闭前，f1窗体是阻断状态的

Answer 9

可是我是在登陆成功后就把第一个窗体关闭后才执行f2.手dialog的。。