Transcript Web Services

Web Services
(Programming the Internet)
Yingcai Xiao
What is it?
What it is for?
Examples
How to write one?
What’s inside?
How does it work?
Web Services
Client 1
Proxy of Interface 2
UDDI Registry 2
SOAP
UDDI Registry 1
Client 2
Proxy of Interface 1
SOAP
Application 1
WSDL Interface 1
Application 2
WSDL Interface 2
WEB
A Web service is an application that exposes Web methods over the Web.
Sharing Objects over the Internet: How?
.
 Transmitting => HTTP (Hypertext Transport Ptotocol
http://www.w3.org/Protocols/)
 Sharing => Standard:
SOAP (Simple Object Access Protocol) for objects
“SOAP is a simple XML-based protocol to let applications
exchange information over HTTP.”
http://www.w3schools.com/soap
http://www.w3.org/TR/SOAP
WSDL (Web Service Definition Language) for services
“WSDL (Web Services Description Language) is an XML-based
language for describing Web services and how to access them.”
http://www.w3schools.com/wsdl/default.asp
 Defining => both are based on XML (Extensible Markup Language,
http://www.xml.com/)
Web Services (XML Web Services) (Outside)
 A Web service is a different kind of Web application.
 It’s not designed to serve end users.
 It’s designed to provide services to other applications
through a highly programmable Internet.
 It doesn’t have a user interface.
 It exposes callable API functions, known as Web methods,
over the Internet.
 .NET Framework makes writing Web services and Web
service clients easy.
 Web services are not the property of Microsoft. They’re an
industry standard built on open protocols such as HTTP
and the Simple Object Access Protocol (SOAP).
 You don’t need the .NET Framework to write Web
services or Web service clients.
Web Services (Inside)

A Web service is an application that:
 Runs on a Web server
 Exposes Web methods to interested callers
 Listens for HTTP requests representing commands to
invoke Web methods
 Executes Web methods and returns the results
 Most Web services expect SOAP messages.
Web Service Examples
Cloud Computing: “is location independent computing, whereby
shared servers provide resources, software, and data to computers
and other devices on demand”
http://en.wikipedia.org/wiki/Cloud_computing
In Cloud Computing, software is in the “cloud”. One of the main
techniques for Cloud Computing is software as a service (SaaS),
which is based on web services.
Web Service Examples
 Amazon Web Services (AWS): http://aws.amazon.com/
Web Services based Cloud Computing at Amazon
Elastic Compute Cloud (Amazon EC2)
provides scalable compute capacity
http://aws.amazon.com/ec2/
Amazon CloudFront :
for content delivery
Alexa Web Information Services
http://www.alexa.com/topsites
Discussion Forums:
http://developer.amazonwebservices.com/connect/forumindex.jspa
Eucalyptus (“Elastic Utility Computing Architecture for Linking Your
Programs To Useful Systems”): http://www.eucalyptus.com/
software platform for implementing private cloud computing using AWS API.
Professional Web Service Examples
Google Apps/AppEngine:
http://code.google.com/appengine/ (Google Cloud: run your web
applications on Google's infrastructure.)
developers.google.com : APIs and Tools for developers
http://code.google.com/ (open source project hosting service)
http://www.google.com/apps (usable applications).
Ways to Write WS

There are many ways to write Web services
 write Web services by hand;
 use SOAP toolkits from Microsoft, IBM, and other companies;
 use the .NET Framework (easy, managed). (need to install IIS and
ASP.NET)
Our First Web Service Using ASP.NET
Calc.asmx
<%@ WebService Language="C#" Class="CalcService" %>
using System;
using System.Web.Services;
[WebService (Name="Calculator Web Service",
Description="Performs simple math over the Web")]
class CalcService
{
[WebMethod (Description="Computes the sum of two integers")]
public int Add (int a, int b)
{
return a + b;
}
Our First Web Service Using ASP.NET
[WebMethod
(Description="Computes the difference between two integers")]
public int Subtract (int a, int b)
{
return a - b;
}
}
Our First Web Service Using ASP.NET

The ASMX file (calc.asmx) is a complete Web service. It
implements two Web methods: Add and Subtract. Both
take two integers as input and return an integer as well.
 Calc.asmx implements two Web methods: Add and
Subtract.
 Deploying: copying it to a web app directory on your
Web server that is URL-addressable (e.g.
C:\inetpub\wwwroot\xiaotest).
 Accessing:
http://winserv1.cs.uakron.edu/xiaotest/calc.asmx.
How a Web Service can be tested
 Web services do not have user interface for
regular users (even though they do have APIs
for programmers.)
 ASP.NET can generate forms to test web
services on the fly from ASMX files.
 Therefore, we don’t have to write special clients
and GUI to test web services when using
ASP.NET.
 But the tests need to be done locally on the
server.
How does the test work?
Example: Calc.asmx
 Users call http://winserv1.cs.uakron.edu/xiaotest/Calc.asmx up in a
browser.
 IIS sends the request to ASP.NET on winserv1.cs.uakron.edu.
 ASP.NET compiles Calc.asmx into a DLL.
 ASP.NET displays a page that users can test the Add method.
 Users Interact with it by clicking the “Add” button.
 ASP.NET finds the method name and signature by reading them from
the metadata in the DLL.
 It generates an HTML form that users can use to call the Add method
with choice of inputs.
 When the users type 2 and 2 into the “a” and “b” boxes and click
Invoke, the XML returned by the Web method appears in a separate
browser window.
Inside Web Services
Inside ASP.NET based Web services
 ASMX is a file name extension registered to ASP.NET in
Machine.config.
 ASMX files begin with @ WebService directives.
 At a minimum, the directive must contain a Class attribute
identifying the class that makes up the Web service.
 Web service classes can be attributed with optional
WebService attributes.
 Web methods are declared by tagging public methods with
WebMethod attributes.
 Helper methods are not exposed by omitting the attribute.
 HTTP, XML, and SOAP are hidden under the hood.
 The Web methods can be invoked with SOAP, HTTP GET,
and HTTP POST.
 They can return output in SOAP responses or simple XML
wrappers.
The WebService Base Class

class CalcService : WebService

WebService belongs to the System.Web.Services
namespace.

It contributes properties named Application, Session,
Context, Server, and User to derived classes.
The WebMethod Attribute

The WebMethod attribute tags a method as a Web
method and supports the following parameters:
Parameter Name
Description
BufferResponse
Enables and disables response
buffering
CacheDuration
Caches responses, in seconds
Description
Adds a textual description to a
Web method
EnableSession
Enables and disables session
state for this Web method (default:
disabled)
MessageName
Specifies the Web method’s name
TransactionOption
Specifies the transactional
behavior of a Web method
The WebMethod Attribute
[WebMethod (EnableSession="true",
Description="Adds an item to a shopping cart")]
public void AddToCart (Item item)
{ ShoppingCart cart = (ShoppingCart) Session["MyShoppingCart"];
cart.Add (item); }
Web methods cannot be overloaded. (Why?)
[WebMethod (MessageName="AddInts")]
public int Add (int a, int b)
{ return a + b; }
[WebMethod (MessageName="AddFloats")]
public float Add (float a, float b)
{ return a + b; }
The Web Services Description Language (WSDL)







A new standard for describing web services.
An XML vocabulary.
For machines to read.
Documented at http://www.w3.org/TR/wsdl.
Need to publish a WSDL contract when publishing a Web service.
Other developers can use the contract to write clients for your Web
service. Wsdl.exe generates a wrapper class containing all the
elements needed to talk to a Web service.
To generate a WSDL contract :
http://winserv1.cs.uakron.edu/xiaotest/Calc.asmx?wsdl
WSDL Contract

A WSDL contract which contains:
 service element that describes the Web service;
 operation elements that document the “operations,” or Web
methods, that the service supports;
 binding elements that document the protocols that the Web
methods support;
 other descriptive information.
Web Services and Complex Data Types
 Complex types are supported.
 Represented in XML using SOAP.
 A client obtains an XML schema describing
the data type from the service’s WSDL
contract.
 Note: WSDL is for describing web services
(special web applications) while SOAP is
for describing web objects. Both use XML
vocabulary. (books, chapters, paragraphs,
English).
Web Services and Complex Data Types
C# Class
public class Bookstore
{
public string Name;
public string Address;
public string City;
public string State;
…
}
SOAP in XML
<s:complexType name="Bookstore">
<s:sequence>
<s:element minOccurs="1" maxOccurs="1" name="Name"
nillable="true" type="s:string" />
<s:element minOccurs="1" maxOccurs="1" name="Address"
nillable="true" type="s:string" />
<s:element minOccurs="1" maxOccurs="1" name="City"
nillable="true" type="s:string" />
<s:element minOccurs="1" maxOccurs="1" name="State"
nillable="true" type="s:string" />
</s:sequence>
</s:complexType>
Web Services and Complex Data Types



You can’t pass complex types to a Web method using
HTTP GET and POST. That’s not a limitation if you use
SOAP to invoke Web methods. (ASP.NET generates
test pages using HTTP GET).
Any fields or properties declared in a class or struct
that’s passed to or from a Web method must be public
if they’re to be serialized (transmitted or saved) when
instances of the class or struct are serialized. That’s
because the .NET Framework’s XML serializer will not
serialize nonpublic members.
Examine a WSDL contract:
http://winserv1.cs.uakron.edu/xiaotest/calc.asmx?wsdl
How to Use/Consume Web Services (WS)
Internal (low-level) code for using web services.
 HTTP commands for using web services through a
web browser.
 How to write a WS client using proxies.
 A console-based WS client.
 An ASP.NET-based WS client.
 For-fee WSs.
 Searching for WSs.

WS Low-level Code
The Web service’s job for responding to each request is to
 receive input from client,
 parse the SOAP envelope containing the inputs,
 compute,
 formulate a SOAP envelope containing the result,
 return it to the client in the body of the HTTP response.
 The WSDL contract is published just once for each web service,
not for each request.
http://winserv1.cs.uakron.edu/xiaotest/calc.asmx?wsdl
• .NET Framework insulates developers from the low-level details
of SOAP, HTTP, and XML and provides a high-level framework
for writing Web services and Web service clients.

WS Low-level Code
Example: a Web service that publishes Web
methods named Add and Subtract at
www.wintellect.com/calc.asmx.
• Before sending a request to the web service, the
client needs to know the services provided by the
web service by reading its WSDL contract.
• http://tempuri.org/ provides namespaces for XML
Web Services under development.

WS Low-level Code
A client sent a request to add 2 and 2 to the “Add” Web method using SOAP.
POST /calc.asmx HTTP/1.1
Host: www.wintellect.com
Content-Type: text/xml; charset=utf-8
Content-Length: 338
SOAPAction: "http://tempuri.org/Add"
<?xml version="1.0" encoding="utf-8"?>
<soap:Envelope
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:xsd=http://www.w3.org/2001/XMLSchema
xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/">
<soap:Body>
<Add xmlns="http://tempuri.org/">
<a>2</a>
<b>2</b>
</Add>
</soap:Body>
</soap:Envelope>
WS Low-level Code
• And here’s how the Web service would respond using SOAP:
HTTP/1.1 200 OK
Content-Type: text/xml; charset=utf-8
Content Length: 353
<?xml version="1.0" encoding="utf8"?>
<soap:Envelope
xmlns:xsi=http://www.w3.org/2001/XMLSchemainstance
xmlns:xsd=http://www.w3.org/2001/XMLSchema
xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/">
<soap:Body>
<AddResponse xmlns="http://tempuri.org/">
<AddResult>4</AddResult>
</AddResponse>
</soap:Body>
</soap:Envelope>
WS Using HTTP GET
 .NET Framework also allows Web methods to be invoked using
ordinary HTTP GET and POST commands instead of SOAP.
This is a non-OO approach and can’t take care of ComplexType
objects.
Using Get:
GET /calc.asmx/Add?a=2&b=2 HTTP/1.1 Host: www.wintellect.com
The Web service responds as follows:
HTTP/1.1 200 OK
Content-Type: text/xml; charset=utf-8
Content-Length: 80
<?xml version="1.0" encoding="utf-8"?>
<int xmlns="http://tempuri.org/">4</int>
WS Using HTTP POST
Here’s a POST command that adds 2 and 2:
POST /calc.asmx/Add HTTP/1.1
Host: www.wintellect.com
Content-Type: application/x-www-form-urlencoded
Content-Length: 7
a=2&b=2
And here’s the Web service’s response:
HTTP/1.1 200 OK
Content-Type: text/xml; charset=utf-8
Content-Length: 80
<?xml version="1.0" encoding="utf-8"?>
<int xmlns="http://tempuri.org/">4</int>
Writing Clients to
Consume
Web Services
Web Services
Client 1
Proxy of Interface 2
UDDI Registry 2
SOAP
UDDI Registry 1
Client 2
Proxy of Interface 1
SOAP
Application 1
WSDL Interface 1
Application 2
WSDL Interface 2
WEB
A Web service is an application that exposes Web methods over the Web.
Web Service Clients & Proxies
Web service clients—applications that use, or
consume, Web methods.
Web Service Proxies
 A Web service proxy is an object that
provides a local representation of a remote
Web service.
 A proxy is instantiated in the client’s own
application domain, but calls to the proxy flow
through the proxy and out to the Web service
that the proxy represents.
Web Service Clients & Proxies
 Calling the corresponding Web service is a simple
matter of calling methods on the proxy.
CalculatorWebService calc = new CalculatorWebService ();
int sum = calc.Add (2, 2);
 When you call one of these methods, the proxy
packages up the input parameters and invokes the
Web method using the protocol encapsulated in the
proxy (typically SOAP).
 The proxy insulates you from the low-level details of
the Web service and of the protocols that it uses. It
even parses the XML that comes back and makes the
result available as managed types.
Generation of a Web Service Proxy

The wsdl.exe utility that comes with the .NET Framework SDK
generates Web service proxy classes from WSDL contracts.
http://msdn.microsoft.com/en-us/library/aa529578.aspx

For Web services written with .NET:
All Programs->…-> Visual Studio Command Prompt
cd to the directory you are going to write your client
wsdl http://winserv1.cs.uakron.edu/xiaotest/calc.asmx
(use V.S. 2010 Command Prompt on winsrev1 )
In the lab:
Z:
mkdir ws
cd ws
wsdl http://winserv1.cs.uakron.edu/xiaotest/calc.asmx

For Web services not written with .NET:
find the WSDL contract (calc.wsdl), then wsdl calc.wsdl
Generation of a Web service proxy



Wsdl.exe generates a CS file containing a class that
represents the Web service proxy.
Use the class to invoke the Web service’s methods.
The proxy class’s name comes from the service name.
Example:
[WebService (Name="Calculator Web Service")]
The resulting <service> tag in the WSDL contract looks like this:
Name=Calculator_x0020_Web_x0020_Service
The resulting proxy class is named CalculatorWebService.
Wsdl.exe switches:
/out:Calc.cs
/language:vb
/namespace:Calc
/protocol:httpget
/protocol:httppost
/proxy:http://myproxy
A Simple Web Service Client
Write a console client (not a web client) for web service Calc.asmx.
1.
Use Wsdl.exe to create a proxy class for Calc.asmx.
wsdl http://winserv1.cs.uakron.edu/xiaotest/calc.asmx
wsdl.exe responds by creating a file named
CalculatorWebService.cs
which contains the proxy class.
2.
Create a new text file named CalcConsoleClient.cs to use the
proxy class.
using System;
class MyApp
{ public static void Main ()
{ CalculatorWebService calc = new CalculatorWebService ();
int sum = calc.Add (2, 2);
Console.WriteLine ("2 + 2 = " + sum);
}}
A Simple Web Service Client
3.
Compile the CS files into a console application:
csc CalcConsoleClient.cs CalculatorWebService.cs
4.
Run CalcConsoleClient.exe.
5. The WS client program instantiates a Web service proxy, calls
the service’s Add method, and displays the result.
Write an ASP client for Calc.asmx
1.
2.
Create a proxy class for Calc.asmx the same way as above.
Create a new CS file named CalcASPClient.cs to use the
proxy class.
using System; using System.Web.UI;
using System.Web.UI.WebControls;
public class CalcASPClient : Page
{ protected Label Sum;
protected TextBox op1, op2;
public void OnAdd (Object sender, EventArgs e)
{ int a = Convert.ToInt32 (op1.Text);
int b = Convert.ToInt32 (op2.Text);
CalculatorWebService calc = new CalculatorWebService ();
int c = calc.Add (a, b); Sum.Text = c.ToString ();
}
Write an ASP client for Calc.asmx
3.
Compile the CS files into a dll for code behind:
csc /target:library /out:bin\CalcASPClient.dll
CalcASPClient.cs CalculatorWebService.cs
4. Create a new ASP file named CalcASPClient.aspx file to use
the code behind.
<%@ Page Inherits="CalcASPClient" %>
<html> <body> <form runat="server">
<asp:TextBox ID="op1" RunAt="server" /> +
<asp:TextBox ID="op2" RunAt="server" />
<asp:Button Text="=" OnClick="OnAdd" RunAt="server" />
<asp:Label ID="Sum" RunAt="server" />
</form> </body> </html>
Write an ASP client for Calc.asmx
5.
Create a web application directory: CalcClient.
6.
Access the “client” through a browser.
http://winserv1.cs.uakron.edu/xiaotest/CalcClient/CalcASPClient.aspx
The event flow when the user clicks to add:
User->
Web Client (a browser)->
Web Server (IIS) where Web app CalcASPClient.aspx is ->
ASP.NET->
ASP Application (CalcASPClient.aspx and
CalcASPClient::OnAdd)->
Web Service Proxy (CalculatorWebService::Add) ->
Web Server (IIS) where Calc.asmx is->
ASP.NET->
Web Service (CalcService::Add)->
Web Service Client (Web Server (IIS) where
CalcASPClient.aspx is) ->
Web Client of Web Application CalcASPClient.aspx ->
User.
The CityView Application
 A real Web application as a Web service client.
 The Web service is the Microsoft TerraService
(msrmaps.com/terraservice2.asmx).
 It is a Web service front end to the Microsoft TerraServer
database.
 TerraServer (msrmaps.com) is one of the world’s largest online
databases of photographs and maps of the Earth’s surface.
 TerraService exposes TerraServer’s content via Web methods.
Its WSDL contract is available at
http://msrmaps.com/terraservice2.asmx?wsdl
 http://winserv1.cs.uakron.edu/xiaotest/CityView/CityView.aspx
Web Services and More
Code-Behind
Asynchronous
For-fee
Web Services and Code-Behind
 Coding: Calc2.asmx:
<%@ WebService Class="CalcService" %>
 Calc.cs: contains the class code and needs to be
compiled into bin\Calc.dll.
 Deploying: Root must be a web application directory (WSCalc). http://localhost/calc2.asmx
 Benefits: (a) Catches compilation errors before the
service is deployed. (b) Enables to write Web services in
languages that ASP.NET doesn’t natively support.
Asynchronous Method Calls


An asynchronous call returns immediately, no matter how
long the Web service requires to process the call.
To retrieve the results from an asynchronous call, you
make a separate call later on by setting up a callback
function.
AsyncCallback cb = new AsyncCallback (AddCompleted);
IAsyncResult res = calc.BeginAdd (2, 2, cb, null);
public void AddCompleted (IAsyncResult res)
{ int sum = calc.EndAdd (res); }
For-Fee Web Services
Authenticate Web Service Callers:
 Assign authorized callers an authentication key and
require them to pass the key in each method call.
 Transmit user credentials in HTTP Authorization headers.
 Transmit user credentials in SOAP headers.
System.Web.Services.Protocols.SoapHeader
For-Fee Web Services
Server Side:
public class AuthHeader : SoapHeader
{ public string UserName;
public string Password;
}
class SafeService
{ public AuthHeader header;
[WebMethod]
[SoapHeader ("header", Required="true")]
public int Add (int a, int b)
{
if (header.UserName == "jeffpro" &&
header.Password == "imbatman")
return a + b;
else throw new HttpException (401, "Not authorized");
}}
For-Fee Web Services
Client Side:
SafeService calc = new SafeService ();
AuthHeader header = new AuthHeader ();
header.UserName = "jeffpro";
header.Password = "imbatman";
calc.AuthHeaderValue = header;
int sum = calc.Add (2, 2);
For-Fee Web Services
The outgoing SOAP envelope (generated by .NET):
<?xml version="1.0" encoding="utf-8"?>
<soap:Envelope xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:xsd=http://www.w3.org/2001/XMLSchema
xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/">
<soap:Header>
<AuthHeader xmlns="http://tempuri.org/">
<UserName>jeffpro</UserName>
<Password>imbatman</Password>
</AuthHeader>
</soap:Header>
<soap:Body>
<Add xmlns="http://tempuri.org/">
<a>2</a>
<b>2</b>
</Add>
</soap:Body>
</soap:Envelope>
Converting Congo to Web Service
http://winserv1.cs.uakron.edu/xiaotest/Congo-MySQL/Congo.aspx
Congo.aspx : GUI + Event Handlers
Congo.asax: Initialization
Congo.cs: Web Service
Level One: Export methods in ShoppingCart.
[WebMethod (MessageName="AddOrder")]
public void AddOrder (BookOrder Order) { … }
Only Congo.cs code are reused
Converting Congo to Web Service
Level Two: Enabling Sessions
(1) Export methods in ShoppingCart (Congo.cs)
(2) Initialization of ShoppingCart (Congo.asax)
(3) Create WS wrappers for some event handlers too (Congo.aspx)
[WebMethod (EnableSession="true",
Description="Adds an item to a shopping cart")]
public void AddToCart (Item item)
{ ShoppingCart cart = (ShoppingCart) Session["MyShoppingCart"];
cart.Add (item); }
Web Services
Client 1
Proxy of Interface 2
UDDI Registry 2
SOAP
UDDI Registry 1
Client 2
Proxy of Interface 1
SOAP
Application 1
WSDL Interface 1
Application 2
WSDL Interface 2
WEB
A Web service is an application that exposes Web methods over the Web.
Finding Web Services
On a Server (DISCO)
On the Internet (UDDI)
Web Service Discovery—DISCO
How do clients know that a Web service exists?

DISCO (short for “discovery”) is a file-based protocol for
local Web service discovery—that is, for getting a list of
available Web services from DISCO files deployed on
Web servers.

Publish a DISCO file on your Web server that describes
the Web services.

Clients interrogate the DISCO file to find out what Web
services are available and where the services’ WSDL
contracts can be found.

DISCO’s chief disadvantage is that you can’t read a
DISCO file if you don’t have its URL.
Web Service Discovery—DISCO
As an example, to publish two Web services:
http://www.wintellect.com/calc.asmx
http://www.wintellect.com/locator.asmx
Deploy the following DISCO file at a well-known URL on your server.
The contractRef elements identify the URLs of the Web services’
WSDL contracts.
<?xml version="1.0" ?>
<discovery xmlns="http://schemas.xmlsoap.org/disco/"
xmlns:scl="http://schemas.xmlsoap.org/disco/scl/">
<scl:contractRef ref="http://www.wintellect.com/calc.asmx?wsdl"
docRef="http://www.wintellect.com/calc.asmx" />
<scl:contractRef
ref="http://www.wintellect.com/locator.asmx?wsdl"
docRef="http://www.wintellect.com/locator.asmx" />
</discovery>
Web Service Discovery—DISCO
Or deploy a VSDISCO file to enable dynamic discovery. The
following VSDISCO file automatically exposes all ASMX
and DISCO files in a host directory and its subdirectories,
with the exception of those subdirectories noted with
exclude elements:
<?xml version="1.0" ?>
<dynamicDiscovery
xmlns="urn:schemas-dynamicdiscovery:disco.2000-03-17">
<exclude path="_vti_cnf" />
<exclude path="_vti_pvt" />
</dynamicDiscovery>
Web Service Discovery—UDDI
 UDDI (Universal Description, Discovery,
and Integration) is a global (Internet)
Web service directory that is itself
implemented as a Web service.
 Developed by IBM, Microsoft, and Ariba.
 A specification for building distributed
databases that enable interested parties
to “discover” each other’s Web services.
 No one company owns the databases;
anyone is free to publish a UDDI-based
business registry.
 Operator sites have already been
established by IBM and Microsoft.
Web Service Discovery—UDDI
 UDDI sites are themselves Web service sites.
 They publish a pair of SOAP-based APIs:
an inquiry API for inquiring about companies
and their Web services
a publisher API for advertising a company’s
Web services (operator sites typically limit
the publisher API to registered members).
 Most developers will use high-level tools to
query UDDI business registries and generate
wrapper classes that allow them to place calls
to the Web services.
Referencing Web Services in Visual Studio .NET
•
Project->Add Service Reference->Advanced->Add Web Reference
•
URL: http://winserv1.cs.uakron.edu/xiaotest/ws/Calc.asmx?wsdl
•
Go (you should see the service description and methods)
•
Web reference name:
CalcService (any name you want for the name space for the proxy)
•
Add Reference
•
View->Class View to explore the classes
•
In your forms1.cs file
using your-project-name-space.CalcService
CalculatorWebService calcws;
calcws = new
CalculatorWebService ();
Dawn of a New Era
 True cross-platform distributed computing based on HTTP,
XML, and SOAP.
Summary:
 Web Services (Architecture), Web Methods, WSDL,
SOAP, XML, DISCO, UDDI, Web Service Clients (Stand
Alone, Web Based), Web Service Proxies, For-Fee Web
Services.