1. Fundamentals of WEB Programming

2. The Web
There is no such protocol, called “WEB”, it is a non-technical expression!
HTTP: The protocol used by modern web browsers to access webpages. It is a client-server textual protocol (originally a 7-bit protocol!) that uses host names
Client: The computer that initiates the connection
Server: The computer that accepts the connection and provides the data

3. Subdomain/IP assignments
A DNS zone file
Subdomain/IP assignments

4. How it works? Internet Home network Root NS Provider Home network
facebook.com

5. How to start?
The future owner of facebook.com buys a computer (real or virtual) and subscribes an internet connection
The internet connection must be 7/24, unfiltered, with a static IPv4 address (IPv4 exhausted: , only available from ISPs)
Then the domain name facebook.com must be registered via a domain registrator (registrar), and must be renewed once in every years
The root servers contain every IP-DNS association. Only dedicated (“country- level”) DNS servers can access the root name servers. Every other computer must use the name server provided by the ISP (Alternative: )

6. DNS resolution Send results (or authority info)
Local cache
Send results (or authority info)
Not in cache
Home router
Send results (or authority info)
Not in cache
ISP
Not in cache
Send results (or authority info)
Root / additional DNS

7. Internet vs. WEB Internet marika.hu zoo.com theater.com school.com
receptek.html
cats.html
allatok.html
dogs.html
marika.hu
zoo.com
intro.html
math.html
Internet
faq.html
arts.html
theater.com
school.com

8. WEB: The documents spreaded all over the world can link to each other
Internet vs. WEB
WEB: The documents spreaded all over the world can link to each other
receptek.html
cats.html
allatok.html
dogs.html
marika.hu
zoo.com
intro.html
math.html
Internet
faq.html
arts.html
WEB
theater.com
school.com

9. Three standards hirek allas cimlap.html URL (Uniform Resource Locator)
belfold.html
allas
ajanlatok.html
cimlap.html

10. Three standards HTML (Hyper Text Markup Language)
Document formatter standard
Extensible with other document parts (e.g. styles=CSS, scripts=JS)
<table border = "1">
<tr>
<th>I. hely</th>
<th>II. hely</th>
<th>III. hely</th>
</tr>
<td>Béla</td>
<td>Gizi</td>
<td>Saci</td>
</table>
eredmeny.html
contents
Shown in browser

11. Three standards
HTTP (Hyper Text Transfer Protocol)

12. HTTP Testable from home Execute -> cmd.exe Install telnet:
pkgmgr /iu:"TelnetClient„
Establish TCP connection:
telnet users.nik.uni-obuda.hu 80
Send command:
GET /kovacs.andras/webprog/hello.html HTTP/1.0
Host: users.nik.uni-obuda.hu

13. HTTP GET /kovacs.andras/webprog/hello.html HTTP/1.0 HTTP commands
GET method
We want the contents of the document
URL without hostname
Full path, filename with extension
Version number
1.0 or 1.1
HTTP/2:
published in the end of 2015
13.7% supported in May 2017

14. HTTP HTTP methods Method Description HEAD GET POST PUT DELETE
Get only the HTTP headers
GET
Get the whole document
POST
Send data to server (form data, can encode files too)
PUT
Send file to the server (Historically. Now: REST API)
DELETE
Remove file from the server (Historically. Now: REST API)

15. HTTP HTTP is a stateless protocol – no built-in session management
By default, every request is connection:close
Even when using connection pooling, two requests cannot be paired
Solution: cookies/sessions
Local vs server-side storage

16. Cookies
OE NIK PHP/Symfony

17. Session
OE NIK PHP/Symfony