Chapter 15Remoting

Yingcai Xiao

• ASP.NET is for building traditional thin-client applications (Web applications).

• Such applications rely on browsers to display HTML generated on servers.

• Benefits:1. shorter development cycles2. more scalable3. more maintainable4. more robust

.

ASP.NET

XML Web Services

Proxy of Interface 2

Client 2

Application 1

UDDI Registry 1

WSDL Interface 1

UDDI Registry 2

Application 2 WSDL Interface 2

SOAP

SOAP

WEB

Proxy of Interface 1

Client 1

WS Class, Contract, Registry, Proxy. XML/HTML: inefficient communication, limited representation power.

• Remoting is for closely coupled applications with a tighter coupling of client and server.

• Such applications have their own client programs and don’t depend on browsers to communicate with the servers. They are “rich-client” applications and distributed applications.

• Better suited for two-way communication between clients and servers than are conventional Web applications.

• Closely coupled applications utilize network bandwidth more efficiently because they can use lean binary protocols in lieu of HTTP.

• “Rich-clients” can use Windows forms to better overcome the limitations of HTML.

• Close coupling facilitates stateful connections between clients and servers, which in turn simplifies the task of building stateful applications.

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Remoting

• Closely coupled applications building tools: – DCOM (Distributed Component Object Model),– CORBA (Common Object Request Broker Architecture), – Java RMI (Remote Method Invocation).

• .NET Remoting: System.Runtime.Remoting is for building closely coupled rich-client applications without the hassles that come with COM programming—apartments, IDL (Interface Definition Language), reference counting, lack of exception handling, incompatible languages and data types, and so on.

• .NET remoting is a better COM than COM.

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Remoting

Basics Remoting begins with the class or classes you want to remote.

A remotable class can be used by clients in other application domains, which can mean other application domains in the client’s process, application domains in other processes, or application domains on other machines.

To write a remotable class, all you have to do is derive from System.MarshalByRefObject.

Both client and server are applications in their own domains.

Basics When a client creates a remote instance of RemotableClass,

the .NET Framework creates a proxy in the client’s application domain.

The proxy looks and feels like the real object. Calls received by the proxy, however, are transmitted to the remote object through a channel connecting the two application domains.

We say that an object served by a proxy has been marshaled by reference because the object isn’t copied to the client’s application domain; the client merely holds a reference to the object. That reference is the proxy.

A remote object needs a server process register the remotable class so that it can be activated from another application domain.

Remoting Architecture

ExampleA simple remote class.

ClockServer.cs

using System;

public class Clock : MarshalByRefObject

{

public string GetCurrentTime ()

{

return DateTime.Now.ToLongTimeString ();

}

}

Communication Client and server communicate usually through a TCP

channel. Each TCP channel is identified by an IP address and a port

number.winserv1.cs.uakron.edu:1234

Each open channel needs to be registered on the server to accept port calls.

Binding also needs to be registered to specify which program to on the server handles the calls.

Binary communication, more efficient than HTTP. The communicate channel can be HTTP too. The other possible type of channel is named pipes.

ExampleA simple remoting server: TimeServer.cs

using System;

using System.Runtime.Remoting;

using System.Runtime.Remoting.Channels;

using System.Runtime.Remoting.Channels.Tcp;

class MyApp

{

static void Main ()

{

//Create and register a channel

TcpServerChannel channel = new TcpServerChannel (1234);

ChannelServices.RegisterChannel (channel);

Example//Set the “Clock” class to be used remotely

RemotingConfiguration.RegisterWellKnownServiceType

(typeof (Clock), "Clock", WellKnownObjectMode.SingleCall);

Console.WriteLine ("Press Enter to terminate...");

Console.ReadLine ();

}

}

ExampleA simple client: TimeClient.cs

using System;

using System.Runtime.Remoting;

using System.Runtime.Remoting.Channels;

using System.Runtime.Remoting.Channels.Tcp;

class MyApp

{

static void Main ()

{

//Create a channel to connect to the server

TcpClientChannel channel = new TcpClientChannel ();

ChannelServices.RegisterChannel (channel);

Example

//Get the “Clock” class to be used.

RemotingConfiguration.RegisterWellKnownClientType

(typeof (Clock), "tcp:/winserv1.cs.uakron.edu:1234/Clock");

//Create and use a “Clock” object as if it was local.

Clock clock = new Clock ();

Console.WriteLine (clock.GetCurrentTime ());

}

}

ExampleBuild and run the example.

csc /t:library clockserver.cs

csc /r:clockserver.dll timeserver.cs

csc /r:clockserver.dll timeclient.cs

Start TimeServer first (in a console window)

Run TimeClient (in another console window).

.NET 3.0, 3.5, 4.0

WCF, WPF, WF, CardSpace, LINQ,

Task Parallel

Windows Communication Foundation

(WCF)

WCF: Windows Communication Foundation

• For distributed applications.

• Using service oriented architecture (SOA).

• Clients can consume multiple services; Services can be consumed by multiple clients. (M:M)

• Services have WSDL interface.

• WCF examples: WSS (Web Services Security, extension to SOAP to apply security to web services), WS-Discovery (Web Services Dynamic Discovery, a multicast discovery protocol to locate services),

WCF: Windows Communication Foundation

• Endpoints: client connects to a WCF service at an Endpoint, each service exposes its contract via endpoints.

• End point ABC: address, binding, contract

• WCF endpoints use SOAP envelope to communicate with clients (for platform independence).

• Behaviors allow the developer to customize how the messages are handled.

Windows Presentation Foundation

(WPF)

WCF: Windows Presentation Foundation

• Graphical subsystem.

• Based on DirectX

• 2D and 3D graphics, vector graphics and animation

• Remote or standalone

• Safe remote view with IE.

• Uses XAML to define UI elements.

• XAML: eXtensible Application Markup Language

Windows Workflow Foundation

(WF)

WF: Windows Workflow Foundation

• Workflow: a series of distinct programming steps.

• An activity at each step.

• Workflow Designer in Visual Studio.• Workflow engine: scheduling, managing, tracking workflows.• To create applications that execute an ordered business

process (UA curriculum proposal approval system).

Windows CardSpace

Windows CardSpace

• Identification metasystem.• Resistance to phishing attacks• Follow the “7 laws of identity” (User Control and Consent,

Minimal Disclosure for a Constrained Use, Justifiable Parties, Directed Identity, Pluralism of Operators and Technologies, Human Integration, Consistent Experience Across Contexts)

• To be replaced by U-Prove.

LINQ

Language Integrated Query

Embedded SQL in C# as strings

StringBuilder builder = new StringBuilder ();

builder.Append ("select count(*) from users " +

"where username = \'");

builder.Append (username);

builder.Append ("\' and pwd = \'");

builder.Append (password);

builder.Append ("\';");

MySqlCommand command = new MySqlCommand (builder.ToString (), connection);

Int64 count = (Int64) command.ExecuteScalar ();

LINQ: Language Integrated Query

var results = from c in SomeCollection

where c.SomeProperty < 10

select new {c.SomeProperty};

foreach (var result in results) Console.WriteLine(result);

Task Parallel

Parallel Extensions

• Managed concurrency library• TPL: Task Parallel Library

• PLINQ: Parallel LINQ

• Multithreading based.• Take advantages of muti-core (Intel) and many core (Nvidia GPU)

That’s all. Folks.