Introduction to the Web and.net

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1 Introduction to the Web and.net This material is based on the original slides of Dr. Mark Sapossnek, Computer Science Department, Boston University, Mosh Teitelbaum, evoch, LLC, and Joe Hummel, Lake Forest College Outline Internet Technologies Programming Web & Distributed Applications.NET Overview

2 Internet Technologies The World Wide Web A way to access and share information Technical papers, marketing materials, recipes,... A huge network of computers: the Internet Graphical, not just textual Information is linked to other information Application development platform Shop from home Provide self-help applications for customers and partners... Internet Technologies WWW Architecture Client PC/Mac/Unix + Browser Request: Network TCP/IP Server Response: <html> </html> Web Server

3 Internet Technologies WWW Architecture Client/Server, Request/Response architecture You request a Web page e.g. HTTP request The Web server responds with data in the form of a Web page HTTP response Web page is expressed as HTML Pages are identified as a Uniform Resource Locator (URL) Protocol: http Web server: Web page: default.asp Can also provide parameters:?name=keith Internet Technologies Web Standards Internet Engineering Task Force (IETF) Founded 1986 Request For Comments (RFC) at World Wide Web Consortium (W3C) Founded 1994 by Tim Berners-Lee Publishes technical reports and recommendations

4 Internet Technologies Hypertext Markup Language (HTML) The markup language used to represent Web pages for viewing by people Designed to display data, not store/transfer data Rendered and viewed in a Web browser Can contain links to images, documents, and other pages Not extensible Derived from Standard Generalized Markup Language (SGML) HTML 3.2, 4.01, XHTML 1.0 Internet Technologies HTML Forms Enables you to create interactive user interface elements Buttons Text boxes Drop down lists Check boxes User fills out the form and submits it Form data is sent to the Web server via HTTP when the form is submitted

5 Internet Technologies Hypertext Transport Protocol (HTTP) The top-level protocol used to request and return data E.g. HTML pages, GIFs, JPEGs, Microsoft Word documents, Adobe PDF documents, etc. Request/Response protocol Methods: GET, POST, HTTP 1.0: simple HTTP 1.1: more complex Internet Technologies HTTP Request Method File HTTP version Headers GET /default.asp HTTP/1.0 Accept: image/gif, image/x-bitmap, image/jpeg, */* Accept-Language: en User-Agent: Mozilla/1.22 (compatible; MSIE 2.0; Windows 95) Connection: Keep-Alive If-Modified-Since: Sunday, 17-Apr-96 04:32:58 GMT Blank line Data none for GET

6 Internet Technologies HTTP Response HTTP version Status code Reason phrase Headers HTTP/ OK Date: Sun, 21 Apr :20:42 GMT Server: Microsoft-Internet-Information-Server/5.0 Connection: keep-alive Content-Type: text/html Last-Modified: Thu, 18 Apr :39:05 GMT Content-Length: 2543 Data <HTML> Some data... blah, blah, blah </HTML> Internet Technologies HTTP Server Status Codes Code Description OK Created Moved Permanently Moved Temporarily Bad Request not understood Unauthorized Forbidden not authorized Not Found Internal Server Error

7 Internet Technologies HTTP HTTP is a stateless protocol Each HTTP request is independent of previous and subsequent requests Statelessness has a big impact on how scalable applications are designed Internet Technologies Cookies A mechanism to store a small amount of information (up to 4KB) on the client A cookie is associated with a specific web site Cookie is sent in HTTP header Cookie is sent with each HTTP request Can last for only one session (until browser is closed) or can persist across sessions Can expire some time in the future

8 Internet Technologies HTTPS A secure version of HTTP Allows client and server to exchange data with confidence that the data was neither modified nor intercepted Uses Secure Sockets Layer (SSL)/ Transport Layer Security (TLS) Internet Technologies URIs, URLs and URNs Uniform Resource Identifier (URI = URL or URN) Generic term for all textual names/addresses Uniform Resource Locator (URL) The set of URI schemes that have explicit instructions on how to access the resource over the Internet, e.g. http, ftp, gopher Uniform Resource Name (URN) 1) A URI that has an institutional commitment to availability, etc. 2) A particular scheme intended to identify resources e.g. urn:schemas:httpmail:subject

9 Internet Technologies Multipurpose Internet Mail Extensions (MIME) Defines types of data/documents text/plain text/html image/gif image/jpeg audio/x-pn-realaudio audio/x-ms-wma video/x-ms-asf application/octet-stream Internet Technologies MIME Specifies character sets, e.g. ASCII Supports multi-part messages Originally designed for , but also used in other places, such as HTTP

10 Internet Technologies Networks - Application Layer Telnet: Remote sessions File Transfer Protocol (FTP) Network News Transfer Protocol (NNTP) Simple Network Management Protocol (SNMP) Simple Mail Transfer Protocol (SMTP) Post Office Protocol (POP3) Interactive Mail Access Protocol (IMAP) Internet Technologies Extensible Markup Language (XML) Represents hierarchical data A meta-language: a language for defining other languages Extensible Useful for data exchange and transformation Simplified version of SGML

11 Outline Internet Technologies Programming the Web.NET Overview Programming the Web Client-Side Code What is client-side code? Software that is downloaded from Web server to browser and then executes on the client Why client-side code? Better scalability: less work done on server Better performance/user experience Create UI constructs not inherent in HTML Drop-down and pull-out menus Tabbed dialogs Cool effects, e.g. animation Data validation

12 DHTML DHTML = Dynamic HTML It allows you to build rich client interfaces and to modify them dynamically There is no DHTML standard It is not a W3C, IEEE, ISO or anything else standard DHTML is a collection of several standards DHTML consists of HTML/XHTML, CSS, DOM and JavaScript (or ECMAScript) Programming the Web Server-Side Code What is server-side code? Software that runs on the server, not the client Receives input from URL parameters HTML form data Cookies HTTP headers Can access server-side databases, servers, files, mainframes, etc. Dynamically builds a custom HTML response for a client

13 Programming the Web Server-Side Code Why server-side code? Accessibility You can reach the Internet from any browser, any device, any time, anywhere Manageability Does not require distribution of application code Easy to change code Security Source code is not exposed Once user is authenticated, can only allow certain actions Scalability Web-based 3-tier architecture can scale out Programming the Web Server-Side Technologies Common Gateway Interface (CGI) Internet Server API (ISAPI) Netscape Server API (NSAPI) Active Server Pages (ASP) Java Server Pages (JSP) Personal Home Page (PHP) Cold Fusion (CFM) ASP.NET

14 Programming the Web Server-Side Programming HTTP request (form data, HTTP header data) HTTP response HTML, XML (static HTML, server-side logic) Outline Internet Technologies Programming Languages and Paradigms Programming the Web.NET Overview

15 .NET Overview Introduction to.net Web Services The.NET Framework Common Language Runtime Windows Forms Web Forms ADO.NET Languages Introduction to.net What is.net? A vision of how information technology will evolve A platform that supports the vision A business model of software as a service

16 A vision Introduction to.net What is.net? Web sites will be joined by Web services New smart devices will join the PC User interfaces will become more adaptable and customizable Enabled by Web standards A platform Introduction to.net What is.net? The.NET Framework Visual Studio.NET.NET Enterprise Servers Database, Messaging, Integration, Commerce, Proxy, Security, Mobility, Content Management.NET Web Services as Building Blocks Goal: make it incredibly easy to build powerful Web applications and Web services

17 A business model Introduction to.net What is.net? Software as a service Subscription-based services Application hosting, e.g. bcentral Introduction to.net The.NET Platform Clients Applications Web Form Web Service Protocols: HTTP, HTML, XML, SOAP, UDDI.NET Framework Windows Tools: Visual Studio.NET, Notepad Your Internal Web Service.NET Foundation Web Services Third-Party Web Services.NET Enterprise Servers

18 Web Services A programmable application component accessible via standard Web protocols The center of the.net architecture Exposes functionality over the Web Built on existing and emerging standards HTTP, XML, SOAP, UDDI, WSDL, Web Services Evolution of the Web HTML, XML HTML HTML HTML, XML Generation 1 Static HTML Generation 2 Web Applications Generation 3 Web Services

19 The.NET Framework What Is the.net Framework? A set of technologies for developing and using components to create: Web Forms Web Services Windows Applications Supports the software lifecycle Development Debugging Deployment Maintenance The.NET Framework The.NET Framework and Visual Studio.NET VB C++ C# JScript Common Language Specification ASP.NET: Web Services and Web Forms ADO.NET: Data and XML Windows Forms.NET Framework Base Classes Visual Studio.NET Common Language Runtime

20 Services Description Discovery Protocols Caching Configuration OLEDB Design Collections Configuration Diagnostics Globalization The.NET Framework.NET Framework Classes System.Web System.Data UI HtmlControls WebControls Security SessionState SQL SQLTypes IO Net Reflection Resources System System.Windows.Forms Form Button MessageBox Drawing2D Imaging XSLT XPath Security ServiceProcess Text Threading ListControl System.Drawing Printing Text System.Xml Serialization Runtime InteropServices Remoting Serialization Common Language Runtime Goals Development services Deep cross-language interoperability Increased productivity Deployment services Simple, reliable deployment Fewer versioning problems NO MORE DLL HELL Run-time services Performance Scalability Availability Reliability Security Safety

21 Common Language Runtime Compilation Source Code Assembly C++, C#, VB or any.net language Compiler csc.exe or vbc.exe DLL or EXE Common Language Runtime Assemblies Assembly Logical unit of deployment Contains Manifest, Metadata, MSIL and resources Manifest Metadata about the components in an assembly (version, types, dependencies, etc.) Type Metadata Completely describes all types defined in an assembly: properties, methods, arguments, return values, attributes, base classes,

22 Common Language Runtime Assemblies Microsoft Intermediate Language (MSIL, IL) All languages compile to IL (managed code) IL is always compiled to native code before being executed Resources E.g..bmp,.jpg Common Language Runtime Execution Model Source code VB Compiler C# Compiler C++ Compiler MSIL Assembly Assembly Assembly Ngen Common Language Runtime JIT Compiler Native code Managed Code CLR Services Managed Code CLR Managed Code Unmanaged Code Operating System Services

23 Assemblies 1 assembly = 1 or more compiled classes.exe represents an assembly with classes + Main program.dll represents an assembly with classes code.vb code.vb code.cs Development Tools assembly.exe /.DLL.NET development There are currently 3 ways to develop assemblies: 1).NET Framework SDK free (100 MB) complete set of command-line tools and docs available for Windows NT, 2000, XP Pro, other platforms? FreeBSD / Mac OS X via Rotor (i.e. SSCLI) Linux via Mono project

24 Development options, cont'd 2) Visual Studio.NET 5-6 CDs, 192 MB RAM (bare minimum) powerful, integrated development environment (IDE) one IDE for all: GUI, web-based, web service, DLLs, etc. this is what 99% of the world uses $$ MSDNAA reduces cost to $800/year for unlimited access 3) free IDEs #develop, a simplified clone of VS.NET WebMatrix, for building web-based applications Hello World in C# Here's the source code: /* hello.cs */ public class Startup { public static void Main() { System.Console.WriteLine("Hello World!"); } }//class hello.cs

25 Why System.Console prefix? In.NET, all code & data must live within a module / class Often nested within namespaces to help organize things a namespace is really just a named collection Example: System.Console.WriteLine("Hello World!"); System namespace in FCL Console class WriteLine subroutine Compiling and running To compile C# with Framework SDK, use the C# compiler c:\> csc /t:exe hello.cs Microsoft (R) Visual C#.NET Compiler version for Microsoft (R).NET Framework version Copyright (C) Microsoft Corporation All rights reserved. open Visual Studio.NET command prompt window to set path csc is the command-line C# compiler use /t:exe option to specify console-based EXE as target c:\> hello.exe Hello World!

$(i.e. generic asm) ILDasm = IL Disassembler c:\> ildasm hello.exe IL?$ Very similar to Java bytecodes: generic assembly language stack-based

26 Viewing an assembly with ILDasm IL = Microsoft's Intermediate Language (i.e. generic asm) ILDasm = IL Disassembler c:\> ildasm hello.exe IL? Very similar to Java bytecodes: generic assembly language stack-based strictly typed no direct memory addressing verifiable for safe execution

Development on FreeBSD Working on FreeBSD is exactly the same! i.e. same command-line tools as Framework SDK produces *binary-compatible*.dll and.exe files!

27 Development on FreeBSD Working on FreeBSD is exactly the same! i.e. same command-line tools as Framework SDK produces *binary-compatible*.dll and.exe files! Class-based development: Example Here's the source code for a simple Customer class: /* customer.cs */ public class Customer { public string Name; public int ID; // fields public Customer(string name, int id) { this.name = name; this.id = id; } public override string ToString() { return "Customer: " + this.name; } }//class // constructor // method

28 Main class Here's the source code for Main, using our Customer class: /* main.cs */ public class App { public static void Main() { Customer c; c = new Customer("joe hummel", 94652); System.Console.WriteLine( c.tostring() ); } }//class Compiling and running application Compile and run as before /out: option specifies name of resulting EXE in this case we are building monolithic app (single EXE, no DLLs) c:\> csc /t:exe /out:app.exe main.cs customer.cs Microsoft (R) Visual C#.NET Compiler version for Microsoft (R).NET Framework version Copyright (C) Microsoft Corporation All rights reserved. c:\> app.exe Customer: joe hummel

29 Component-based development: Example Let's rebuild previous app based on components Customer class ==> DLL Main class ==> EXE main.cs customer.cs app.exe + customer.dll Compiling a component Use the C# compiler with /t:library option to specify component library as target csc produces a DLL in this case c:\> csc /t:library customer.cs Microsoft (R) Visual C#.NET Compiler version for Microsoft (R).NET Framework version Copyright (C) Microsoft Corporation All rights reserved. c:\> dir *.dll customer.dll

$reference also stored inside assembly so CLR can locate c:\> csc /t:exe /out:app.exe main.cs /r:customer.dll Microsoft (R) Visual C#.NET Compiler version 7.00.$ $9466 for Microsoft (R).NET Framework version 1.0.3705 Copyright (C) Microsoft Corporation 2001. All rights reserved. c:\> app.$

30 Compiling and running application Compile using C# compiler as before, except reference component so compiler can locate Customer class! reference also stored inside assembly so CLR can locate c:\> csc /t:exe /out:app.exe main.cs /r:customer.dll Microsoft (R) Visual C#.NET Compiler version for Microsoft (R).NET Framework version Copyright (C) Microsoft Corporation All rights reserved. c:\> app.exe Customer: joe hummel To run, use name of assembly containing Main CLR follows reference to locate DLL Where are references stored? Within assembly as part of assembly manifest Visible via ILDasm c:\> ildasm app.exe

31 mscorlib = "ms-core-lib" Core FCL assembly mscorlib? contains core system classes like string contains System.Console class for console-based I/O Automatically referenced for us by C# compiler All assemblies must be present.exe.dll.dll.dll OS Process JIT Compiler other FCL assemblies obj code obj code obj code obj code Core FCL assembly CLR Underlying OS and HW

Introduction to the Web and.net

Introduction to the Web and.net This material is based on the original slides of Dr. Mark Sapossnek, Computer Science Department, Boston University, Mosh Teitelbaum, evoch, LLC, and Joe Hummel, Lake Forest