Network
Internet
History
- Before www, there was internet, computer connect each other, but hard to communicate each other
- In 1989 www invented by Tim Berners-Lee: a protocol (common language computer can speak)
- Internet is a phone, www is an application
- In 1991 first website was created
What happens when you click a website?
Click google ⮕
ISP (internet service provider) ⮕
DNS (domain name server) like a phone book store the address of google.com IP address ⮕
send back to browser
Browser send IP address ⮕
google servers (like a computer, store file) ⮕
server send HTML CSS Javascript file to the browser
How to transmit data:
Router ⮕ Modem of the house ⮕ ISP ⮕internet backbone (physical cable) ⮕ servers
How to make visit website fast:
- Location of server (nearer faster)
- How many trips
- Size of file
Internet Protocols
HTTP, HTTPS
Reference: W3S
HTTP(Hypertext Transfer Protocol) works as a request-response protocol between a client and server.
Example: A client (browser) sends an HTTP request to the server; then the server returns a response to the client.
Request consist of:
-
Headers
-
Body
-
Method
Most used methods are:
- GET
- POST(add)
- PUT(update)
- DELETE - browser can use query strings (the string after the
?of website link in the address bar) or the body to send request
Response consist of:
-
Headers
-
Status
HTTPS: communication between client(browser) and server is encryted.
JSON, XML
They are data formats used for communication between client and server when HTTP protocol is used.
XML: HTML like syntax.
JSON: object like syntax.
// JSON object methods in Javascript
var obj = JSON.parse({"name":"Bob","age":29})
var myJSON = JSON.stringify(obj)
AJAX
- A way browser make request to server.
- Without AJAX everytime need to update the page, need to refresh the whole page.
- Now it can only update a small proportion dynamically.
Usage example in Javascript:
- Old way: XML HTTP request
- New: jQuery
-
Newer:
fetch('url').then()// fetch can have its own json convert .then(response => response.json())