WCF websocket

WebSocket

, like as TCP, is a bi-directional, full-duplex communication channel over a single TCP connection but it shortens abundant complications close to bi-directional communication as well as connection management which we typically comprehend while using TCP.

WebSocket

channels start as normal HTTP channels which are then upgraded to

WebSocket

channels by using handshaking, allowing cooperative TCP communication between client and server.

WCF hosts provision for

WebSockets

over the standard HTTP ports 80 and 443. The standard HTTP port allows

WebSockets

to communicate across the web through mediators. WCF introduces two standard bindings to support communication over a

WebSocket

transport.

NetHttpBinding

NetHttpsBinding

These bindings are designed for consuming

WebSocket

services and will perceive whether they are used with a request-reply contract or duplex contract and change their behavior according to it. They will use HTTP/HTTPS for request-reply contracts and

WebSockets

for duplex contracts. We can override this behavior by using

WebSocketTransportUsage

setting:

Always

– Enforce to use

WebSockets

Never

– Stops to use

WebSockets

WhenDuplex

– This is the default value.

Define Callback Contract

public interface INotificationServiceCallback
{
[OperationContract(IsOneWay = true)]
void OnNotificationSend(Notification notification);
}

Clients will implement this contract through which the service can send messages back to the clients. To have a better understanding how duplex channel works, I would recommend you to have a look at this link.

Define Service Contract

[ServiceContract(CallbackContract = typeof(INotificationServiceCallback))]
public interface INotificationService
{
[OperationContract]
void SendNotification(Notification notification);

[OperationContract]
void SubscribeForNotification
(List<NotificationType> notificationTypes);

[OperationContract]
void UnsubscribeForNotification
(List<NotificationType> notificationTypes);
}

Here,

INotificationServiceCallback

has been specified as the callback contract.

Implement Service Contract

public class NotificationServiceService : INotificationService
{
private INotificationServiceCallbackSubscriber
{
get { return OperationContext.Current.
GetCallbackChannel<INotificationServiceCallback>();  }
}

public void SendNotification(Notification notification)
{
NotificationManager.Instance.SendNotification(notification, Subscriber);
}

public void SubscribeForNotification
(List<NotificationType> notificationTypes)
{
NotificationManager.Instance.AddSubscriber(Subscriber, notificationTypes);
}

public void UnsubscribeForNotification
(List<NotificationType> notificationTypes)
{
NotificationManager.Instance.RemoveSubscriber(Subscriber, notificationTypes);
}
}

In the implementation, we retain the callback channel using the

OperationContext

which has been passed to the

NotificationManager

and finally

NotificationManager

does the rest of the Jobs.

Implement Notification Manager

public class NotificationManager
{
private volatile static NotificationManager_notificationManager = null;
private static readonly object SyncLock = new object();
private NotificationManager()
{
Subscribers = new Dictionary
<INotificationServiceCallback, List<NotificationType>>();
Notifications = new List<Notification>();
}

public Dictionary<INotificationServiceCallback,
List<NotificationType>> Subscribers { get; private set; }
public List<Notification> Notifications { get; private set; }
public static NotificationManagerInstance
{
get
{
lock (SyncLock)
{
if (_notificationManager == null)
{
lock (SyncLock)
{
_notificationManager = new NotificationManager();
}
}
}
return _notificationManager;
}
}

public void AddSubscriber(INotificationServiceCallbacksubscriber,
List<NotificationType> notificationType)
{
if (!Subscribers.ContainsKey(subscriber))
Subscribers.Add(subscriber, notificationType);
else
{
var newNotificationType = notificationType.Where
(n => Subscribers[subscriber].Any(n1 => n1 != n));
Subscribers[subscriber].AddRange(newNotificationType);
}
}

public void RemoveSubscriber(INotificationServiceCallback
subscriber, List<NotificationType> notificationTypes)
{
if (Subscribers.ContainsKey(subscriber))
{
notificationTypes.ForEach(notificationType =>
Subscribers[subscriber].Remove(notificationType));

if (Subscribers[subscriber].Count < 1)
Subscribers.Remove(subscriber);
}
}

public void AddNotification(Notification notification)
{
if (!Notifications.Contains(notification))
Notifications.Add(notification);
}

public void RemoveNotification(Notification notification)
{
if (Notifications.Contains(notification))
Notifications.Remove(notification);

}

public void SendNotification
(Notification notification, INotificationServiceCallbacksender)
{
foreach (var existingSubscriber in Subscribers)
{
if (existingSubscriber.Value.Any(n =>
n == notification.NotificationType) &&
existingSubscriber.Key != sender)
{
if (((ICommunicationObject)existingSubscriber.Key).
State == CommunicationState.Opened)
{
existingSubscriber.Key.OnNotificationSend(notification);
}
}
}
}
}

As we see,

NotificationManager

maintains a dictionary to hold the client list that have been subscribed for getting the notifications for different notification types. If any client broadcast messages with Notification types, the subscribers who only subscribe to get the notification for these notification types will get these messages. The code is itself self-explanatory. If you go through the code portion, you will easily have an idea about that.

Service Configuration

<?xml version="1.0" encoding="UTF-8"?>
<configuration>
<system.web>
<compilation debug="true" targetFramework="4.5" />
<httpRuntime targetFramework="4.5" />
</system.web>
<system.serviceModel>
<protocolMapping>
<add scheme="http" binding="netHttpBinding" />
</protocolMapping>
<behaviors>
<serviceBehaviors>
<behavior name="">
<serviceMetadata httpGetEnabled="true"
httpsGetEnabled="true" />
<serviceDebug includeExceptionDetailInFaults=
"false" />
</behavior>
</serviceBehaviors>
</behaviors>
<serviceHostingEnvironment aspNetCompatibilityEnabled="true"
multipleSiteBindingsEnabled="true" />
</system.serviceModel>
<system.webServer>
<directoryBrowse enabled="true" />
</system.webServer>
</configuration>

NetHttpBinding

has been used for the default endpoints. If you want to acquaint yourself a bit more about the configuration updates, I would suggest having a look at that.

Okay Service Portion has been done. Now, let's move at the client portions,

Implement Callback Contract and Define Client

class Program : INotificationServiceCallback
{
private NotificationServiceClient _notificationServiceClient;
private InstanceContext_instanceContext;
private readonly List<NotificationType>
_notificationTypes = Enum.GetValues(typeof(NotificationType)).
Cast<NotificationType>().ToList();

public NotificationServiceClient NotificationServiceClient
{
get
{
return _notificationServiceClient ??
(_notificationServiceClient =
new NotificationServiceClient(CallbackInstance,
"netHttpBinding_INotificationService"));
}
}

public InstanceContextCallbackInstance
{
get { return _instanceContext ??
(_instanceContext = new InstanceContext(this)); }
}

static void Main(string[] args)
{
var objProgram = new Program();
Console.WriteLine("Write exit to shut down....\n");
Console.WriteLine("Wait...Subscribing for notifications\n");
objProgram.SubscribeForNotification();
Console.WriteLine("Subscription done...
Now you can send notifacation\n");
var readMsg = Console.ReadLine();

while (readMsg.ToString(CultureInfo.InvariantCulture).
ToLower().Equals("exit") == false)
{
objProgram.SendNotification(readMsg);
Console.WriteLine("Notification has been send......\n");
readMsg = Console.ReadLine();
}
objProgram.UnsubscribeForNotification();
}

public void OnNotificationSend(Notification notification)
{
Console.WriteLine(string.Format("New Notification Received\
n\nMessage :{0}\nTime :{1}\n\n", notification.
NotificationMsg, notification.PostingTime));
}

private void SubscribeForNotification()
{
NotificationServiceClient.SubscribeForNotification(_notificationTypes);
}

private void UnsubscribeForNotification()
{
NotificationServiceClient.UnsubscribeForNotification(_notificationTypes);
}

private void SendNotification(string msg)
{
NotificationServiceClient.SendNotification(new Notification()
{
NotificationMsg = msg,
PostingTime = DateTime.Now
});
}
}

The client application has a property of

InstanceContext

and

NotificationServiceClient

, also it specifies the implementation of the

INotificationServiceCallback

interface. When a client subscribes for the notifications to the service, the service will send the notifications to the client using the callback contract specified.

Implement Service Client

    public class NotificationServiceClient :
DuplexClientBase<INotificationService>, INotificationService
{
public NotificationServiceClient(InstanceContextcallbackInstance) :
base(callbackInstance)
{
}

public NotificationServiceClient(InstanceContext
callbackInstance, string endpointConfigurationName) :
base(callbackInstance, endpointConfigurationName)
{
}

public void SendNotification(Notification notification)
{
Channel.SendNotification(notification);
}

public void SubscribeForNotification
(List<NotificationType> notificationTypes)
{
Channel.SubscribeForNotification(notificationTypes);
}

public void UnsubscribeForNotification
(List<NotificationType> notificationTypes)
{
Channel.UnsubscribeForNotification(notificationTypes);
}
}

Client Configuration

<?xml version="1.0"?>
<configuration>
<system.serviceModel>
<bindings>
<netHttpBinding>
<binding name="NetHttpBinding_INotificationService">
<webSocketSettings transportUsage="Always" />
</binding>
</netHttpBinding>
</bindings>
<client>
<endpoint address="ws://localhost/websocket/NotificationService.svc"
binding="netHttpBinding"
contract="Rashim.RND.WCF.WebSockect.Interfaces.INotificationService"
bindingConfiguration="NetHttpBinding_INotificationService"
name="netHttpBinding_INotificationService">
<identity>
<dns value="localhost" />
</identity>
</endpoint>
</client>
</system.serviceModel>
</configuration>

This is as usual and not anything special, what you need to do in the client configuration is to specify the client side endpoint using the

NetHttpBinding

.

Finally DataContracts

[DataContract]
public class Notification
{
[DataMember]
public string NotificationMsg { get; set; }
[DataMember]
public DateTime PostingTime { get; set; }
[DataMember]
public NotificationType NotificationType { get; set; }
}

[DataContract]
public enum NotificationType
{
[EnumMember]
General,
[EnumMember]
Greetings
}

Using the Source Code

You need to host the

Rashim.RND.WCF.WebSockect.Services

in IIS8 and then put the appropriate endpoint address to the client configuration file. After completing the Service hosting, you need to run the two instances of

Rashim.RND.WCF.WebSockect.Clients

, then you can send message from instance to another one just like the given figure below:

References

http://msdn.microsoft.com/en-us/library/hh674271.aspx

http://msdn.microsoft.com/en-us/library/hh674273.aspx

http://msdn.microsoft.com/en-us/library/hh977020.aspx

http://rashimuddin.wordpress.com/2012/09/30/171/

http://rashimuddin.wordpress.com/2013/04/06/duplex-service-in-wcf/

原文：http://www.codeproject.com/Articles/613677/WebSocket-in-WCF

继承DuplexClientBase类，初始化时关联WCF，并进行业务扩展。

WCF提供相关的数据服务和回调接口，通过OperationContext.Current.GetCallbackChannel获取通道对象，调用回调方法。