一起谈.NET技术，Siverlight与WCF通信之双工netTcp实现视频对话

　　效果

　　先看看效果再说，基本逻辑是两个人通过Silverlight端，借助TCP协议分别向服务器不断传输视频，服务器接收到视频后，会检测这些视频是发给谁的，然后回调某个客户端来接收并显示这些视频。

　　实现

　　双工的服务契约定义：

[ServiceContract(CallbackContract=typeof(IChatServiceCallBack))]
public interface IChatService
{
[OperationContract]
void SendVideo(UserVideo userVideo);
}
[ServiceContract]
public interface IChatServiceCallBack
{
[OperationContract(IsOneWay=true)]
void GetVideos(List<UserVideo> listVideos);
}

　　数据契约，由三部分组成，发送者，接受者和视频流，方便服务器进行判断，选择接收的回调句柄。

[DataContract]
public class UserVideo
{
[DataMember]
public string UserName { get; set; }
[DataMember]
public string PartnerName { set; get; }
[DataMember]
public byte[] VideoByte { set; get; }
}

　　既然是双工的，当然我们还需要定义一个客户端的回调句柄类，包括两个属性，一个是客户端名称，一个是回调句柄：

public class ClientHandler {

public string Name { set; get; }

public IChatServiceCallBack Client { set; get; } }

　　服务实现，这里没有采用定时检测视频集合，而是在每次有客户端上传视频时进行检测并回调客户端来接收，这样做的好处是事件驱动，比定时检测更具有准确性。

public class ChatService : IChatService
{
static List<ClientHandler> listOfClientHandler = new List<ClientHandler>();
private static List<UserVideo> listVideos = new List<UserVideo>();
IChatServiceCallBack client;
public void SendVideo(UserVideo userVideo)
{
Console.WriteLine("receiving...");
listVideos.Add(userVideo);

client = OperationContext.Current.GetCallbackChannel<IChatServiceCallBack>();
if (listOfClientHandler.Where(m => m.Name == userVideo.UserName).Count() == 0)
{
listOfClientHandler.Add(new ClientHandler() { Name=userVideo.UserName, Client=client });
}

foreach(var item in listOfClientHandler)
{
if (listVideos.Where(m => m.PartnerName == item.Name).Count() > 0)
{
var videos = listVideos.Where(m => m.PartnerName == item.Name).ToList();
item.Client.GetVideos(videos);
Console.WriteLine("sending...");
listVideos.RemoveAll(m => m.PartnerName == item.Name);//处理一个视频后直接从服务器上删除此视频
}
}
}
}

　　客户端，基本原理是先发送视频，然后定义回调函数来处理服务器的回调：

void btnSendVideo_Click(object sender, RoutedEventArgs e)
{
System.Windows.Threading.DispatcherTimer timer = new System.Windows.Threading.DispatcherTimer();
timer.Interval = new TimeSpan(0, 0, 0, 0, 200);
timer.Tick += new EventHandler(timer_Tick);
timer.Start();
}

void timer_Tick(object sender, EventArgs e)
{
proxy = new ChatServiceClient();
proxy.GetVideosReceived += new EventHandler<GetVideosReceivedEventArgs>(proxy_GetVideosReceived);
WriteableBitmap bmp = new WriteableBitmap(this.rectangleUser, null);
MemoryStream ms = new MemoryStream();
EncodeJpeg(bmp, ms);
UserVideo userVideo = new UserVideo();
userVideo.PartnerName = this.Partner;
userVideo.UserName = this.User;
userVideo.VideoByte = ms.GetBuffer();
proxy.SendVideoCompleted += (se,ev) => { };
proxy.SendVideoAsync(userVideo);
}

void proxy_GetVideosReceived(object sender, GetVideosReceivedEventArgs e)
{
foreach (ChatService.UserVideo video in e.listVideos)
{
MemoryStream ms = new MemoryStream(video.VideoByte);
BitmapImage bitmap = new BitmapImage();
bitmap.SetSource(ms);
imagePartner.Source = bitmap;
ms.Close();
}
}

　　app.config配置：

<system.serviceModel>
<bindings>
<netTcpBinding>
<binding name="netTcpBindConfig"
closeTimeout="00:01:00"
openTimeout="00:01:00"
receiveTimeout="00:10:00"
sendTimeout="00:01:00"
transactionFlow="false"
transferMode="Buffered"
transactionProtocol="OleTransactions"
hostNameComparisonMode="StrongWildcard"
listenBacklog="10"
maxBufferPoolSize="2147483647 "
maxBufferSize="2147483647 "
maxConnections="10"
maxReceivedMessageSize="2147483647 ">
<readerQuotas maxDepth="32"
maxStringContentLength="2147483647 "
maxArrayLength="2147483647 "
maxBytesPerRead="4096"
maxNameTableCharCount="16384" />
<reliableSession ordered="true"
inactivityTimeout="00:10:00"
enabled="false" />
<security mode="None">
</security>
</binding>
</netTcpBinding>
</bindings>
<services>

<service behaviorConfiguration="Server.ChatServiceBehavior" name="Server.ChatService">
<host>
<baseAddresses>
<add baseAddress="net.tcp://localhost:4503/ChatService"/>
</baseAddresses>
</host>
<endpoint address="" binding="netTcpBinding" contract="Server.IChatService" bindingConfiguration="netTcpBindConfig"></endpoint>
<endpoint address="mex" binding="mexTcpBinding" contract="IMetadataExchange" ></endpoint>
</service>

</services>
<behaviors>
<serviceBehaviors>
<behavior name="Server.ChatServiceBehavior">
<serviceMetadata/>
<serviceDebug includeExceptionDetailInFaults="false"/>
</behavior>
</serviceBehaviors>
</behaviors>
</system.serviceModel>

　　遗留问题
　　1、由于客户端是定时上传视频流，而非长连接方式，需要不停的调用服务器来上传视频，有些耗资源，并且有时会出现下面的异常，猜想是由于不停的连接导致。

　　2、wcf传输方式配置的是transferMode="Buffered"，这种方式并不适合流式传输。实时性上仍有待改进。

　　源码下载：http://files.cnblogs.com/wengyuli/chatTCPduplex.rar