Module 3: Remoting and XML Web Services

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Module 3 Remoting and XML Web Services
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Overview

• Remoting
• Remoting Configuration Files
• XML Web Services

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Remoting

• Remoting Overview
• Channels and Formatters
• Activation and Proxies
• Lease-Based Lifetime
• Object Marshaling
• Server Side
• Client Side
• Client Compilation Techniques

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Remoting Overview
Client AppDomain
Server AppDomain
Formatter
Formatter
Client Object
Server Object
Channel
Channel
Server Proxy
Remoting Boundary
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Channels and Formatters

• Channels Transport Messages To and From Remote
  Objects
• Client Selects a Channel That Is Registered on
  the Server
• Before calling a remote object, the client
  registers the channel Channels are registered on
  a per application domain basis
• One computer cannot have multiple channels
  listening to same port
• .NET Provides Implementation of HTTP and TCP
  Channels
• HTTP Channel default SOAP protocol to transport
  XML messages
• TCP Channel defaultTCP protocol to transport
  binary messages
• Faster than HTTP SOAP Web Services but not
  as open
• Example Programmatic Registration of TCP Channel
  on Port 8085

using System.Runtime.Remoting.Channels using
System.Runtime.Remoting.Channels.Tcp TcpChannel
chan new TcpChannel(8085) ChannelServices.Regi
sterChannel(chan)
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Activation and Proxies

• Before Using a Remote Object, the Client Must
  Activate It
• By calling new, Activator.CreateInstance, or
  Activator.GetObject
• Activation Returns Proxy Used by Client to Access
  Remote Object
• Proxy represents remote object in clients
  AppDomain
• Proxy forwards clients calls, and returns
  results and exceptions
• Server-Side Activation Automatic Instantiation
  by Server
• Single call object handles only one request
  (stateless)
• Singleton object services multiple clients and
  requests (stateful)
• Client-Side Activation Instantiation by
  Explicit Client Call
• State maintained between method calls for
  specific client instance

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Object Marshaling

• Objects Instantiated Remotely Are Returned by
  Reference and Accessed by the Client Through a
  Proxy
• Remote Call Parameters, Return Values, and Fields
  Can Be
• Marshal-by-value objects A copy of the object
  is passed from one AppDomain to another
• - Value types and classes that are serializable
• Marshal-by-reference objects A reference to the
  object is passed from one AppDomain to another
• - Classes that derive from the System.MarshalByRef
  Object class
• Not-marshaled objects Objects suitable for
  local use only
• - Any class that is not Marshal-By-Value or
  Marshal-By-Reference

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Server Side

• Register the Channel
• Register Remote Objects by Using
• The RegisterWellKnownServiceType call
• Or a configuration file

RemotingConfiguration.RegisterWellKnownServiceType
( typeof(HelloServer), "SayHello",
WellKnownObjectMode.SingleCall)
RemotingConfiguration.Configure("MyHello.exe.confi
g")
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Client Side

• Register the Channel
• Activate Remote Object by Using
• Activator.GetObject
• new and a configuration file

ChannelServices.RegisterChannel(new
TcpChannel())
HelloServer obj (HelloServer)Activator.GetObject
( typeof(RemotingSamples.HelloServer), "tcp//lo
calhost8085/SayHello")
RemotingConfiguration.Configure("MyHello.exe.confi
g") HelloServer obj new HelloServer()
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Client Compilation Techniques

• When the Client Is Compiled, the Compiler Needs
  Server Class Data
• Class Information Can Be Provided by
• A reference to the assembly where the class is
  stored
• Splitting the remote object into an
  implementation class and an interface type
• Using Wsdl.exe to extract the required metadata
  directly from the endpoint

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Remoting Configuration Files

• Configure Method on RemotingConfiguration
• An Application Configuration File is an XML
  Document
• Configuration files are case-sensitive
• Can be specified on a machine or on an
  application level
• Application level configuration takes
  priority over machine level configuration
• For more information see Remoting Configuration
  File Format in the .NET Framework SDK
  documentation

RemotingConfiguration.Configure(foo.exe.config)
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Demonstration Remoting
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XML Web Services

• ASP.NET XML Web Services Overview
• ASP.NET Features
• Consuming an XML Web Service
• XML Web Service Discovery

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What Is an XML Web Service?
A programmable application component accessible
via standard Web protocols
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ASP.NET XML Web Services Overview

• ASP.NET Files with .asmx Extensions Are Web
  Services
• Example of HelloWorld .asmx File
• If File Is Placed on Server Foo Inside a Virtual
  Directory Bar
• Access service by using
• Access WSDL of service by using

lt_at_ WebService Language"C" Class"HelloWorld"
gt using System using System.Web.Services public
class HelloWorld WebService  
WebMethod public String SayHelloWorld()
return "Hello World"
http//Foo/Bar/HelloWorld.asmx
http//Foo/Bar/HelloWorld.asmx?wsdl
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ASP.NET Features

• ASP.NET Can Expose Web Services Defined in a .NET
  Class
• Class derives from WebService, method attribute
  WebMethod
• Class source file is compiled into a library DLL
  and placed in \Bin
• The .asmx file contains a single line that names
  the class
• Advanced ASP.NET Features
• Data sets, Global.asax, Session and Application
  objects, pattern matching

namespace MyNameSpace public class HelloWorld
WebService WebMethod public String
SayHelloWorld() return "Hello
World"
csc /outbin\helloworld.dll /tlibrary
helloworld.cs
lt_at_ WebService Class"MyNameSpace.HelloWorld" gt
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Demonstration Using Visual Studio .NET to Create
an XML Web Service
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Consuming an XML Web Service

• To Consume a Web Service, Use Wsdl.exe
• Identify the object or service URI to be used
• Run Wsdl.exe on the services URI
• Write the client code that calls the remote
  object
• Build the client and proxy code

http//localhost/MathService/Service1.asmx
wsdl http//localhost/MathService/Service1.asmx?ws
dl
Service1 salesTaxService new Service1() float
totalAmount salesTaxService.SalesTax( amount,ta
xRate)
csc salestaxclient.cs service1.cs
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XML Web Service Discovery

• Discovery The Process of Locating and
  Interrogating XML Web Service Descriptions
• Discovery Services Are Evolving and Changing
  Rapidly
• Disco Microsoft XML Web Services Discovery Tool
  
• Disco file is an XML document that links to
  descriptions of XML Web Services
• Disco file is currently created and used by
  Visual Studio
• Universal Description, Discovery, and Integration
  Project
• Open framework for describing services,
  discovering businesses, and integrating business
  services that use the Internet
• Cross-industry support and platform independence
• For more information, see http//www.uddi.org