HTML and The Internet Flashcards
IP
- each device has unique IP address
- IPv4, IP address represented as 4 “8 bit” integer in range 0,255
Static IP
IP reserved for a given device
Dynamic IP
IP allocated to device when it connects to the internet
Local IP
addressable only on a private network
- local IPS can often still access open internet through proxy servers or gateways, gateways have connection to the global internet
External IP
directly addressable from anywhere on the internet
Hostnames
- Hierarchical to domain name
- Top Level Domain (TLD) e.g. .au
- hostnames resole to IP address via Domain Name System (DNS) using “name servers”
2 hostnames, same IP address
2 servers on same computer
1 hostname, multiple IP address
big servers like youtube
Structure of Internet
- devices address each other by iP but communicate via Internet routers
- communication from client to server
Applications and ports
- multiple apps run over IP networks e.g. email, messenger
- machines communicate with other machines over the internet via collection of numbered ports, differentiated by application
e. g. 25 = outgoing mail, 110 = incoming mail - to identify which application wants which port
URL
- uniform resource locators
- internet resources addressed with URLs
scheme: //hostname:port/path - scheme = protocol for accessing file
- hostname = device the file lives on
- port = access port (optional)
- path = where file lives on device
HTML
- Hypertext markup language
- primary language used to markup web documents
- elements = tag,s entities
- tags may optionally contain attributes
Line breaks
<br></br>
Horizontal breaks
<hr></hr>
hyperlinks
<a></a><a></a>
Absolute URL
complete URL including hostname
Relative URL
relative to current location on same server
. = current directory
.. = parent directory
- more flexible
Dynamically generating a webpage
“serving” printer HTML output of Python script
