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