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Overview. Internet Internet Protocols Fundamentals about HTTP Communication HTTP-Server, mode of operation Static/Dynamic Webpages HTML PHP programming. Internet. Internet. Server. Text, Audio, Video and Gra phics. Connection via TCP/IP - Proto c o l. Client. History.

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Overview
Overview

  • Internet

  • Internet Protocols

  • Fundamentals about HTTP Communication

  • HTTP-Server, mode of operation

  • Static/Dynamic Webpages

  • HTML

  • PHP programming

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Internet

Internet

Internet

Server

Text, Audio, Video

and Graphics

Connectionvia

TCP/IP-Protocol

Client

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History
History

  • The WWW is 18 years old

  • On the 30th April 1993 the originator of the WWW Tim Berners-Lee declared: Everyone is allowed to use the World Wide Web and all possibilities it offers without any licenses. Eine gute Idee.

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Internet services

Internet

Internet Services

  • E-Mail

  • WWW

  • Chat

  • Internet News

  • FTP

  • Telnet

  • Applications

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Internet protocols

Internet

Internet Protocols

Server

  • HTTP

  • HTTPS

  • FTP

  • SMTP

  • NNTP

Data

Connection via

Internet Protocol

Client

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Protocols
Protocols

HTTP

FTP

SMTP

DNS

SNMP

RIP

Application

TCP

UDP

Transport

IP

Internet

Ethernet

Token-Ring

ATM

Phys. Network

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Http hypertext transfer protocol
http (Hypertext Transfer Protocol)

  • Two Types of http messages: Request, Response

  • Requests:

    • Request method i.e.: Get, Post

    • wanted URL

    • HTTP-Protocol version (actual 1.1)

    • Headerinfo i.e.: which documents could be received by the client

  • Responses:

    • Status messages i.e.: 200 : OK, 404: File Not Found

    • Headerinfo i.e.: Content-Length, Content-Type (Text, Html, etc.)

    • The requested document

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Http interaction
http (Interaction)

  • HTTP Interaction Principles :

    • Connection establishmentTCP-Connection from Client to Server (usually Port 80 on the Server)

    • Request from Client to ServerMethod selectionadditional parameters for the method

    • Response from Server to ClientResult as a status codeadditional parameters on the result

    • Connection terminationusually ending the connectionnewer versions (newer then HTTP/1.1) can keep connection longer alive

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Http methods
http (Methods)

  • OPTIONS requests server features

  • GET fetch a resource from server

  • HEAD provides only meta information about a resource

  • PUT saves a resource

  • POST sends a data set to a resource (CGI-Script)

  • DELETE deletes a resource

  • TRACE allows tracking of the processing of requests

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Https 1
https (1)

  • Widely used security technology

  • http-Server accepts ssl (secure socket-layer) connection

  • Identification of secure connection viahttps://url

  • SSL connection uses port 443

  • Transmitted data are quasi tap-proof (key length)

  • Higher working load on server, because encryption causes additional computing time

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Https 2
https (2)

HTTPS

Application

SSL

Security

TCP

Transport

IP

Internet

Ethernet

Token Ring

ATM

Phys. Network

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Client server principle
Client Server Principle

Client withWebbrowser

Webserver

Request over

http request

Results

HTTP

http answer

IP-Adresse

TCP/IP

TCP/IP

Netzwerk

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Overview
URL

  • URL = unified resource locator

  • The access to the server is done by the URL

  • Format:access_method://computerername:port/document?querystring

  • Example:http://www.uni-duisburg.de/netlab/student.php?matr=123456

    • access method: http

    • computer name: fb9dv.uni-duisburg.de

    • port: standard port (80 for HTTP), here not specified

    • document: netlab/students.html (path/filename)

    • Query string: matr=123456

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Domain names

de

uni-duisburg.de

fb9dv.uni-duisburg.de

Domain names

  • Domain name: fb9dv.uni-duisburg.de

    • de: first layer name (top-level-domain)

    • uni-duisburg: second layer name

    • fb9dv: third layer name

iis.uni-duisburg.de

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Port communication
Port communication

  • communication via TCP/IP operates by IP-Addresses and Ports

  • each IP-Adresse has 216 potential ports

  • The ports below 1024 are standardized (standard ports), which are allocated to dedicated services, i.e.:23 telnet25 smtp80 http443 https

134.91.100.1

. . . . . . . .

23

25

80

30000

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Query get post
Query GET/POST

  • Data transfer to server

  • Data are computed by the server and the resulted page is sent to the client

  • Two procedures: Get and Post method

  • Get: Query-String is specified within the url http://www.uni-duisburg.de/student.php?name=peter

  • Post: Data are transmitted in HTTP query’s body (not in url)

    Example: form data

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Http server 1
HTTP-Server (1)

  • Document Root Folderroot directory where all files for the website are stored

  • Documents are organized in directories

  • Access rights are considered read, write, deletepublic accessed web pages have to be readable by everyone, in terms of access rights

  • Definition of standard documents like index.html, start.htm

  • Modular structured, additional services like php-Modul can be integrated

  • Multiple configurations i.e. - directory level control- allow access only from specific IP-Addresses

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Http server 2
HTTP-Server (2)

  • Apache-Server configuration is done using the file httpd.conf. This file is read in and evaluated when starting the servers

  • Contains information about the Apache Web-Server itself, about logs and additional configuration files. Examples:

    • ServerRootThe statement ServerRoot defines the path to the top level directory, which includes configuration folders and files, log-files and documents.

    • DocumentRootThe document folder is the directory, where the server tries to locate the file, in case no path was specified within the url. Only one DocumentRoot can be defined in the resource list of the Apache Web-Servers.

    • UserDirUserDir makes it possible for the web-server to access documents out of the user’s home directory. Example: http:/server/~username/document.htm

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Http server 3
HTTP-Server (3)

Configuration panel for IIS (Windows 2000)

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Static internet pages

Pages (content) are already available before they are requested

Pages are quickly available

The Server does not need any additional services (applications) like: Interpreter, Database.

Interaction with Server is limited to links

Pages can be computed, respectively displayed, on the client computer, without any additional procedures

Static Internet Pages

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Html 1
HTML (1) requested

  • HTML (Hypertext Markup Language)

  • Markup language: it describes the logical part of a text oriented document.

  • HTML offers the possibility to define typical elements of a text oriented document, like: header, paragraphs, lists, tables or graphical references.

  • Advantages:

    • HTML is a so called clear text format (can be edited with every text editor)

    • Easy to learn

  • Disadvantages:

    • No separation between form and content

    • Design and Interaction possibilities are limited

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Html 2
HTML (2) requested

<html>

<head>

<title>Beispiel 1</title>

</head>

<body>

Textfeld<br>

</body>

</html>

Browser

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Dynamic internet pages server1
Dynamic Internet Pages (Server1) requested

  • Page content is generated (immediately) after request

  • Access may be slower, due to the need of page generation

  • System has to have adequate resources

  • Optional applications possible

    • Database access

    • Graphics generation

    • Access of processes (application), which offer interfaces

  • General 2 methods

    • GGI (Common Gateway Interface)i.e.: perl, c++

    • As a modul (server extension)i.e.: php

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Dynamic internet pages server2
Dynamic Internet Pages (Server2) requested

Server

Client

CGI

DB

Request

Generated

HTML-File

Generated

HTML-File

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Dynamic internet pages client
Dynamic Internet Pages (Client) requested

  • DHTML

  • Browser can execute (interpret) scripts, which are included in HTML-Files.

  • By the use of a script language a dynamic page can be created on the client.

  • Example: JavaScript (Browser independent) Alternatively JavaScript can be embedded in the HTML-File or it can be located in a separate file. JavaScript is interpreted by the web browser at runtime. Therefore modern web browser have an interpreter software integrated.Example

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Sessions
Sessions requested

  • HTTP is a stateless protocol

  • After the request (and response) for a web page the connection between client and server is terminated

  • Server do not have a history list or anything similar, which means that two consecutive requests from the same client are treated as two different independent requests

  • How is this problem solved? i.e. online shops

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Sessions 2
Sessions (2) requested

  • Implementation of a mechanism, which generates (on the server) an unique session-ID at the first request. It will be sent with each further client request to the server.

  • Session ID is transmitted

    • Within the URL, which means each link, used within a session, includes the session-ID

    • With use of cookiesmax 4 KB text files, which are initiated by the server and sent to the client. They can be used by the client on demand.

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Overview
Php requested

  • PHP is an interpreted language

  • Platform independent (Windows/UNIX)

  • Easy Syntax (C-similar)

  • Easy to integrate in http-Servers (Apache, IIS)

  • Powerful functions (database access, graphical libraries, etc)

  • Free Software (no license costs)

  • Frequently used (as well by public providers)

  • A lot of ready-to-use modules (forums, web pages, sample scripts)

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Php structure
PHP: Structure requested

  • PHP can be embedded in HTML documents or used as pure PHP files.

    • The PHP code is between two tags:

      <?php

      and

      ?>

    • The file name has in both cases the extension .php

  • Each command ends in PHP by a semicolon „;“ or by the PHP end tag.

  • Example

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Php comments
PHP: Comments requested

  • Comments in PHP are characterized as follows:

    • By the symbol # or // Denotes the following text, until the end of the line as a comment.

    • by /* … */ Hereby the enclosed text is denoted as a comment.

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Php variables
PHP: Variables requested

  • PHP uses an automatic data type conversion (i.e. integer to string, etc.).

  • Definition:

    • Variables

      $variable_name=“value“

    • Arrays

      $Array_name = array {

      value1,

      value2,

      }

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Php control structures
PHP: Control Structures requested

IF (condition) {

# instructions, if condition is true

}

ELSEIF (further conditions) {

# instructions, if the first condition was false and this condition is true

}

ELSE {

# instructions, if all conditions are false

}

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Php loops
PHP: Loops requested

  • WHILE-loop

    WHILE (condition) {

    # instructions, execute while condition is true

    }

  • FOR-loop

    FOR (start value; condition; instruction) {

    # instructions

    }

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Php functions
PHP: Functions requested

FUNCTION function_name (variables as parameters) {

# instructions

# optional: RETURN (return value);

}

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Php text output
PHP: Text Output requested

  • TEXT (HTML-Code) generation with PHP using the command „PRINT“commands:

    • PRINT („output text“);

    • PRINT ($variable);

    • PRINT ($variable.“output text“);

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Php file operations
PHP: File Operations requested

  • Open file for writing

  • Save data in file

  • Read data from fileImportant: adequate file permissions are required!!!

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Php hand over data
PHP: hand over data requested

  • The array $HTTP_POST_VARS contains all the variables handed over via POST method. i.e.: from a form via POST.

  • The Array $HTTP_GET_VARS contains all the variables handed over via GET method. i.e.: from a form via GET.

  • Example

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Sample program
Sample Program requested

Source-Code

of the example

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Links about php html
Links about PHP/HTML requested

  • PHP developers homepagehttp://www.php.net

  • selfhtml: Excellent document (tutorial) about HTML and morehttp://selfaktuell.teamone.de/

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