Basics of Websockets

Internet Porotocol Suite

{ Application Layer } [ HTTP, Websockets, SSL, IMAP, POP ] { InternetLayer } [ ipv4, ipv6 ] { Transport Layer } [ TCP, UDP ]

The TCP takes care of amking sure all packages reach the destination unaffected and in proper oder The UDP is used for streaming videos and other similar tasks

HTTP is a stateless protocol that is the present state is not depend on

{ HTTP is sateless After the initial request is done, the server-client communication is lost. }

{ Clients specify actions . GET / POST / PUT / DELETE }

{ Data sent with headers Headers sent with request AND response }

{ AJAX asynchronously send data to server without refreshing request-> ____________________________________________________ <- Response

request -> 

Client ___________________________________________________ Server <- Response

request ->
____________________________________________________
					<- Response

can countinue to send data and make request after conection }

WebSockets

{ Full-duplex bi-directional Communication! }

// To switch to websockets you send a header that you wana shift over to websocket
// it uses the same tcp conection that was originaly established
// no headers in socket requests( only sent during initial handshake)
// 
{ webSockets is a HTTP upgrade!
	uses the same TCP connection over ws:// or wss:// }
{ Easy to implement and standardised! }
{ Only sends headers once! }

// caniuse.com check browser compatability

// Alternative to Websockets

Polling and long Polling

{ Alternative to WebSockets 
	Much better backwards compatibillity! }

{ Polling 
	Send AJAX request every x amount of seconds for new data
	(not real time) }
{ Long Pollig
	Send request to server and keep connection open untill new data }

Server sent Events

{ Another "real-time" alternative 
	Uses EventSource API to send messages from server 
	Not truly bi-directional }

{ Generally requires an event loop }

{ No binary message capability }

Intended Use case

{ WebSockets not==replacement for HTTp
	WS is an upgrade for HTTP.
	HTTP provides automatic caching
	WS often needs special configuration for load balancing
	cant communicate with REST }
{ Use when You need full-duplex connection
	Useful web-based games, chatting application,anything 
	which needs low-latency realtime connection! } 

WebSockets CLients

{ USed to interface with WebSocket Servers 
// The Js file that i fetched in script in chat app sort of cdn
	Bulit in many languages(including python) }
{ Most common client is web based and uses javascript }
{ Require the server to be able to interface WS }

Websocket clientside code

const socket = new WebSocket('ws://localhost:8000');

// this fucntion is called when socket is connected
socket.onopen = (event) => {
//on connection, do something..
socket.send("hi hi connectd me "); // sending the string to server
});

//This is called when the server sends back something

socket.onmessage = (event) => {
// message from server
console.log(event.data);
});

SocketIO

Makes the native socket makes then nicer and easier to use
it has certain fallback mechanish. Like if a server and client do 
not agree on a handshake it can fallback to long polling

{ Javascript library for manupulating WebSockets
	includes fallback mechanism and auto-reconnection }
{ Hndles disconnection and connection events }
{ Namespacing and Room broadcasting } // group of clients to talk to 


## clinet side code of socket.io

var socket = io("http://localhost:8000/<MY_NAMESPACE>');

//this connects to the socket server
socket.on('connect', () => {
  socket.emit('event_on_my_server', data="new conection");
});

// custom made events can be sent
socket.on('my_custom_event', (data) => {
  // do something
});

Python Servers w/WebSockets

{ SocketIO with python-socketio: flask, Tornado, Pyramid, Bottle, Sanic, AioHTTP, Tornado } { Native webSockets out of the box sanic,AioHTTP,Tornado with library Flask,Django(Channels 2.0), Bottle }

Native sockets in flask

// import setup application above

socket = Sockets(app)

@socket.route('/my_sockets')
def my_socket_event(WS):
  while not ws.closed:
    message = WS.receive()
    ws.send(message)

SocketIO Server

// you can use custom events and can send to mutliple people that is to a groups
//import setup application above
socket = socketio.Server()

@socket.on('my custom event', namespace='/pycon')
def custom_event(session_id, data):
  // do stuff with data from client, send to all connected tp 'Pycon'
  socket.emit('my event on the server', data, broadcast = True)

app = socketio.Middleware(socket, app)
# start server below

Performance comparision

{ HTTP and websockets have same sized header } // socket only sends its once
{ 2bytes/msgoverhead } // for other messages unlike 
{ SocketIO increaes latency and initial conection
   uder the hood starts:
         uses AJAX long Polling initialy and then upgrades }