本文将在这个案例的基础上，加入一个特殊场景，利用Silverlight来实现客户端。有的朋友可能会说，其实是一样的吧。请不要急于下结论，有用过Silverlight的朋友都有这种体会，很多在标准.NET Framework编程中能用的技术，到了Silverlight里面，或多或少会有些限制。不幸的是，Socket这个功能就是其中一个。这本身没有什么好不好的问题，Silverlight首先是运行在一个特殊的沙盒中，受到一些限制也是意料之中的，毕竟安全第一嘛

我总结Silverlight中应用Socket的几点特殊之处

1.所有的操作都必须的异步的，包括连接，发送和接收消息

2.Silverlight只能做客户端，不能做服务器（虽然这句看起来说的有点多余，不过确实有朋友想这么做呢）

3.Silverlight的Socket只能访问如下端口，4502-4530，只能用TCP。

4.Silverlight的Socket收到访问策略的限制，服务端必须监听，并提供ClientAccessPolicy的支持。通常是在943端口（TCP)进行监听，也可以在HTTP 80端口监听。

本文完整代码如下 http://files.cnblogs.com/chenxizhang/SocketWorkshop(with-silverlight).rar

那么，我们就来通过例子学习一下在Silverlight中如何使用Socket技术与服务端通讯吧

第一步：创建Silverlight项目

第二步：设计Silverlight界面

<UserControl    x:Class="SocketSilverlightClient.MainPage"    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"    mc:Ignorable="d"    d:DesignHeight="300"    d:DesignWidth="400">    <Grid        x:Name="LayoutRoot"        Background="White"        Margin="20">        <Grid.Resources>            <Style                TargetType="Button">                <Setter                    Property="Width"                    Value="100"></Setter>                <Setter                    Property="HorizontalAlignment"                    Value="Left"></Setter>                <Setter                    Property="Margin"                    Value="5"></Setter>            </Style>            <Style                TargetType="TextBlock">                <Setter                    Property="Margin"                    Value="5"></Setter>                <Setter                    Property="HorizontalAlignment"                    Value="Left"></Setter>                <Setter                    Property="TextWrapping"                    Value="Wrap"></Setter>            </Style>        </Grid.Resources>        <StackPanel>            <Button                Content="Connect"                x:Name="btConnect"                Click="btConnect_Click"></Button>            <TextBlock                Text="Type your message"></TextBlock>            <StackPanel                Margin="5"                Orientation="Horizontal">                <TextBox                    x:Name="txtInput"                    Width="200"></TextBox>                <Button                    Content="Send"                    x:Name="btSend"                    Click="btSend_Click"></Button>            </StackPanel>            <TextBlock                Text="Messages from server"></TextBlock>            <ItemsControl                Margin="5"                x:Name="icResult">            </ItemsControl>        </StackPanel>    </Grid></UserControl>

这个界面看起来像下面这样

第三步：编写基本的客户端代码

using System;using System.Collections.Generic;using System.Linq;using System.Net;using System.Windows;using System.Windows.Controls;using System.Windows.Documents;using System.Windows.Input;using System.Windows.Media;using System.Windows.Media.Animation;using System.Windows.Shapes;//导入命名空间using System.Net.Sockets;namespace SocketSilverlightClient{    /// <summary>    /// 演示如何在Silverlight中使用Socket技术    /// 作者：陈希章    /// </summary>    public partial class MainPage : UserControl    {        public MainPage()        {            InitializeComponent();        }        /// <summary>        /// 尝试连接到服务器        /// </summary>        /// <param name="sender"></param>        /// <param name="e"></param>        private void btConnect_Click(object sender, RoutedEventArgs e)        {            //创建一个套接字            var socket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);            //准备一个异步参数（这是特有的）            var args = new SocketAsyncEventArgs();            //设置远程服务器地址，这里用DnsSafeHost，可以获取到宿主远程服务器的主机名称            args.RemoteEndPoint = new DnsEndPoint(App.Current.Host.Source.DnsSafeHost, 4530);            //注册Completed事件处理程序            args.Completed += (o, a) =>            {                if(a.SocketError > 0)//0表示成功，其他的表示有错误                {                    //注意，因为Completed方法是在工作线程触发的，所以要对主线程进行访问，必须使用Dispatcher机制                    this.Dispatcher.BeginInvoke(() =>                    {                        MessageBox.Show("Connect fail:" + a.SocketError.ToString());                    });                }                else                {                    this.Dispatcher.BeginInvoke(() =>                    {                        MessageBox.Show("Connect success");                    });                }            };            //发起异步的连接请求            socket.ConnectAsync(args);        }        private void btSend_Click(object sender, RoutedEventArgs e)        {        }    }}

【注意】在Silverlight中使用Socket的代码，与一般的客户端还是不同的。最主要的区别在于异步模型。

目前，我这里只编写了Connect的代码，是因为这里就会遇到连接问题，其他代码先不着急写出来。我们可以运行起来看看

点击“Connect”之后，我们发现有一个错误，是AccessDenied。这就是说，Silverlight遇到了权限问题无法直接访问到服务器。

我们都知道,Silverlight是运行在一个沙盒里面的，它要访问宿主网站之外的资源，是受到很多限制的。它会先尝试检查目标资源是否有一个ClientAccessPolicy的设置。

这里有一篇详细的介绍 http://msdn.microsoft.com/zh-cn/library/cc197955(VS.95).aspx

第四步：为服务器添加PolicyServer。

已经有不少先进同学在这方面有研究了。这个PolicyServer是负责向Silverlight发送策略信息的，也就是说，Silverlight的Socket，在连接之前，会默认去连接目标主机的943端口，请求ClientAccessPolicy的认证，只有通过了，则可以继续访问其他的Socket。

这个PolicyServer的设计，不是我的原创，但我稍做了修改。请将下面的代码保存为一个独立的文件，放在SocketServer这个项目里面

using System;using System.Configuration;using System.Diagnostics;using System.IO;using System.Net;using System.Net.Sockets;using System.Reflection;using System.Text;namespace SocketServerService{    /// <summary>    /// This is a silverlight socket client access policy file server.    ///     /// Background:    /// When a socket connection open attempt to some server is made in Silverlight 2.0    /// Silverlight automatically makes a request to the server in question on port 943 for a policy file    /// The policy file served includes the valid ports and valid clients for the socket server    ///     /// Outcomes:    /// The socket request will result in success if the client access policy file served by the socket    /// server permits access to the requested port and the client URI is in the <allow-from> element    /// See ClientAccessPolicy.xml & http://msdn.microsoft.com/en-us/library/cc645032(VS.95).aspx for further details    ///     /// The socket request will be denied if the client access policy file is not served or if the client /    /// port is denied in the client access policy file    /// </summary>    class SL_SocketPortPolicyListener    {        TcpListener _Listener = null;        TcpClient _Client = null;        const string _PolicyRequestString = "<policy-file-request/>";        int _ReceivedLength = 0;        byte[] _Policy = null;        byte[] _ReceiveBuffer = null;        EventLog eventLog;        /// <summary>        /// Initializes a new instance of the <see cref="SL_SocketPortPolicyListener"/> class.        /// </summary>        /// <param name="serviceEventLog">The service event log.</param>        public SL_SocketPortPolicyListener(EventLog serviceEventLog)        {            eventLog = serviceEventLog;            Start();        }        /// <summary>        /// 增加的代码        /// </summary>        public SL_SocketPortPolicyListener()            : this(new EventLog("Application"))        {        }        /// <summary>        /// Starts this instance.        /// </summary>        void Start()        {            try            {                //增加的代码                var policyConfig =                    "<?xml version=\"1.0\" encoding =\"utf-8\"?>" +                        "<access-policy>" +                          "<cross-domain-access>" +                            "<policy>" +                              "<allow-from>" +                                "<domain uri=\"*\" />" +                              "</allow-from>" +                              "<grant-to>" +                                "<socket-resource port=\"4502-4530\" protocol=\"tcp\" />" +                              "</grant-to>" +                            "</policy>" +                          "</cross-domain-access>" +                        "</access-policy>";                //删除的代码                //string executionLocation = Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location);                //string policyFile = ConfigurationManager.AppSettings["PolicyFilePath"];                //using(FileStream fs = new FileStream(executionLocation + policyFile, FileMode.Open))                //{                //    _Policy = new byte[fs.Length];                //    fs.Read(_Policy, 0, _Policy.Length);                //}                //增加的代码                _Policy = Encoding.Default.GetBytes(policyConfig);                _ReceiveBuffer = new byte[_PolicyRequestString.Length];                //Using TcpListener which is a wrapper around a Socket                //Allowed port is 943 for Silverlight sockets policy data                _Listener = new TcpListener(IPAddress.Any, 943);                _Listener.Start();                _Listener.BeginAcceptTcpClient(new AsyncCallback(OnBeginAccept), null);            }            catch(Exception exp)            {                LogError(exp);            }        }        /// <summary>        /// Called when [begin accept].        /// </summary>        /// <param name="ar">The ar.</param>        private void OnBeginAccept(IAsyncResult ar)        {            _Client = _Listener.EndAcceptTcpClient(ar);            _Client.Client.BeginReceive(_ReceiveBuffer, 0, _PolicyRequestString.Length, SocketFlags.None,                new AsyncCallback(OnReceiveComplete), null);        }        /// <summary>        /// Called when [receive complete].        /// </summary>        /// <param name="ar">The ar.</param>        private void OnReceiveComplete(IAsyncResult ar)        {            try            {                _ReceivedLength += _Client.Client.EndReceive(ar);                //See if there‘s more data that we need to grab                if(_ReceivedLength < _PolicyRequestString.Length)                {                    //Need to grab more data so receive remaining data                    _Client.Client.BeginReceive(_ReceiveBuffer, _ReceivedLength,                        _PolicyRequestString.Length - _ReceivedLength,                        SocketFlags.None, new AsyncCallback(OnReceiveComplete), null);                    return;                }                //Check that <policy-file-request/> was sent from client                string request = System.Text.Encoding.UTF8.GetString(_ReceiveBuffer, 0, _ReceivedLength);                if(StringComparer.InvariantCultureIgnoreCase.Compare(request, _PolicyRequestString) != 0)                {                    //Data received isn‘t valid so close                    _Client.Client.Close();                    return;                }                //Valid request received....send policy file                _Client.Client.BeginSend(_Policy, 0, _Policy.Length, SocketFlags.None,                    new AsyncCallback(OnSendComplete), _Client.Client);            }            catch(Exception exp)            {                _Client.Client.Close();                LogError(exp);            }            _ReceivedLength = 0;            //listen for the next client            _Listener.BeginAcceptTcpClient(new AsyncCallback(OnBeginAccept), null);        }        /// <summary>        /// Called when [send complete].        /// </summary>        /// <param name="ar">The ar.</param>        private void OnSendComplete(IAsyncResult ar)        {            Socket socket = (Socket)ar.AsyncState;            try            {                socket.EndSend(ar);            }            catch(Exception exp)            {                LogError(exp);            }            finally            {                socket.Close();            }        }        /// <summary>        /// Logs the error.        /// </summary>        /// <param name="exp">The exp.</param>        private void LogError(Exception exp)        {            eventLog.WriteEntry(string.Format("Error in PolicySocketServer: {0} \r\n StackTrace: {1}", exp.Message, exp.StackTrace));        }    }}

然后，在SocketServer的主程序中，加入下面的代码（只需要添加红色这一行即可）

using System;using System.Collections.Generic;using System.Linq;using System.Text;//额外导入的两个命名空间using System.Net.Sockets;using System.Net;namespace SocketServer{    class Program    {        /// <summary>        /// Socket Server 演示        /// 作者：陈希章        /// </summary>        /// <param name="args"></param>        static void Main(string[] args)        {            var policyServer = new SocketServerService.SL_SocketPortPolicyListener();            //创建一个新的Socket,这里我们使用最常用的基于TCP的Stream Socket（流式套接字）            var socket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);            //将该socket绑定到主机上面的某个端口            //方法参考：http://msdn.microsoft.com/zh-cn/library/system.net.sockets.socket.bind.aspx            socket.Bind(new IPEndPoint(IPAddress.Any, 4530));            //启动监听，并且设置一个最大的队列长度            //方法参考：http://msdn.microsoft.com/zh-cn/library/system.net.sockets.socket.listen(v=VS.100).aspx            socket.Listen(4);            //开始接受客户端连接请求            //方法参考：http://msdn.microsoft.com/zh-cn/library/system.net.sockets.socket.beginaccept.aspx            socket.BeginAccept(new AsyncCallback(ClientAccepted), socket);            Console.WriteLine("Server is ready!");            Console.Read();        }        public static void ClientAccepted(IAsyncResult ar)        {            var socket = ar.AsyncState as Socket;            //这就是客户端的Socket实例，我们后续可以将其保存起来            var client = socket.EndAccept(ar);            //给客户端发送一个欢迎消息            client.Send(Encoding.Unicode.GetBytes("Hi there, I accept you request at " + DateTime.Now.ToString()));            //实现每隔两秒钟给服务器发一个消息            //这里我们使用了一个定时器            var timer = new System.Timers.Timer();            timer.Interval = 2000D;            timer.Enabled = true;            timer.Elapsed += (o, a) =>            {                //检测客户端Socket的状态                if(client.Connected)                {                    try                    {                        client.Send(Encoding.Unicode.GetBytes("Message from server at " + DateTime.Now.ToString()));                    }                    catch(SocketException ex)                    {                        Console.WriteLine(ex.Message);                    }                }                else                {                    timer.Stop();                    timer.Enabled = false;                    Console.WriteLine("Client is disconnected, the timer is stop.");                }            };            timer.Start();            //接收客户端的消息(这个和在客户端实现的方式是一样的）            client.BeginReceive(buffer, 0, buffer.Length, SocketFlags.None, new AsyncCallback(ReceiveMessage), client);            //准备接受下一个客户端请求            socket.BeginAccept(new AsyncCallback(ClientAccepted), socket);        }        static byte[] buffer = new byte[1024];        public static void ReceiveMessage(IAsyncResult ar)        {            try            {                var socket = ar.AsyncState as Socket;                //方法参考：http://msdn.microsoft.com/zh-cn/library/system.net.sockets.socket.endreceive.aspx                var length = socket.EndReceive(ar);                //读取出来消息内容                var message = Encoding.Unicode.GetString(buffer, 0, length);                //显示消息                Console.WriteLine(message);                //接收下一个消息(因为这是一个递归的调用，所以这样就可以一直接收消息了）                socket.BeginReceive(buffer, 0, buffer.Length, SocketFlags.None, new AsyncCallback(ReceiveMessage), socket);            }            catch(Exception ex){                Console.WriteLine(ex.Message);            }        }    }}

再次测试，我们就发现Silverlight客户端能够连接到服务器了

既然连接上了服务器，那么就让我们来将Silverlight客户端里面其他的一些功能都实现一下吧

第五步：实现Silverlight客户端的消息收发

using System;using System.Collections.Generic;using System.Linq;using System.Net;using System.Windows;using System.Windows.Controls;using System.Windows.Documents;using System.Windows.Input;using System.Windows.Media;using System.Windows.Media.Animation;using System.Windows.Shapes;//导入命名空间using System.Net.Sockets;using System.Text;namespace SocketSilverlightClient{    /// <summary>    /// 演示如何在Silverlight中使用Socket技术    /// 作者：陈希章    /// </summary>    public partial class MainPage : UserControl    {        public MainPage()        {            InitializeComponent();        }        //创建一个套接字        Socket socket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);        /// <summary>        /// 尝试连接到服务器        /// </summary>        /// <param name="sender"></param>        /// <param name="e"></param>        private void btConnect_Click(object sender, RoutedEventArgs e)        {            //准备一个异步参数（这是特有的）            var args = new SocketAsyncEventArgs();            //设置远程服务器地址，这里用DnsSafeHost，可以获取到宿主远程服务器的主机名称            args.RemoteEndPoint = new DnsEndPoint(App.Current.Host.Source.DnsSafeHost, 4530);            //注册Completed事件处理程序            args.Completed += ConnectCompleted;            //发起异步的连接请求            socket.ConnectAsync(args);        }        /// <summary>        /// 该事件在连接成功时发生        /// </summary>        /// <param name="sender"></param>        /// <param name="args"></param>        public void ConnectCompleted(object sender, SocketAsyncEventArgs e)        {            if(e.SocketError > 0)//0表示成功，其他的表示有错误            {                //注意，因为Completed方法是在工作线程触发的，所以要对主线程进行访问，必须使用Dispatcher机制                this.Dispatcher.BeginInvoke(() =>                {                    MessageBox.Show("Connect fail:" + e.SocketError.ToString());                });            }            else            {                this.Dispatcher.BeginInvoke(() =>                {                    //MessageBox.Show("Connect success");                    //将连接按钮禁用掉                    btConnect.Content = "Connected";                    btConnect.IsEnabled = false;                    var buffer = new byte[1024];                    e.SetBuffer(buffer, 0, buffer.Length);                    e.Completed -= ConnectCompleted;                    e.Completed += ReceiveCompleted;                    socket.ReceiveAsync(e);                });            }        }        /// <summary>        /// 该事件在接收消息时发生        /// </summary>        /// <param name="sender"></param>        /// <param name="args"></param>        public void ReceiveCompleted(object sender, SocketAsyncEventArgs e)        {            //将消息显示在界面上            var result = Encoding.Unicode.GetString(e.Buffer, 0, e.Count);            this.Dispatcher.BeginInvoke(() =>            {                icResult.Items.Add(result);            });            //递归继续接收消息            socket.ReceiveAsync(e);        }        private void btSend_Click(object sender, RoutedEventArgs e)        {            var args = new SocketAsyncEventArgs();            //将用户输入的文本转成字节            var buffer = Encoding.Unicode.GetBytes(txtInput.Text);            args.SetBuffer(buffer, 0, buffer.Length);            //设置远程服务器地址，这里用DnsSafeHost，可以获取到宿主远程服务器的主机名称            args.RemoteEndPoint = new DnsEndPoint(App.Current.Host.Source.DnsSafeHost, 4530);            //发送完成的话，将控件清空，激活            args.Completed += (o, a) => {                this.Dispatcher.BeginInvoke(() =>                {                    txtInput.Text = string.Empty;                    btSend.IsEnabled = true;                });            };            //禁用按钮            btSend.IsEnabled = false;            //发送消息            socket.SendAsync(args);        }    }}

运行起来看看吧

还不错对吧，这个例子给大家演示了如何在Silverlight中使用Socket，接下来大家可以结合自己的现实工作做一些研究和扩展吧

本文完整代码如下 http://files.cnblogs.com/chenxizhang/SocketWorkshop(with-silverlight).rar

转自：http://www.cnblogs.com/chenxizhang/archive/2011/09/10/2173101.html

你得学会并且学得会的Socket编程基础知识（续）——Silverlight客户端