socket.io

Question 1

what is websocket

Answer 1

its just a communicstion protocal like http,ftp,smt

http till now used for api

Question 2

http vs websocket

Answer 2

http - one way : client request and server response to that request . note server can’t send data according to its mood it can send data(resposne) only when there request from the client

websocket - a connection is establish between client and server

it follows duplex communication i.e. even if client is not resquesting anything and connection is still established then server can send data (response) on its own no need of request from client

Question 3

what is io

Answer 3

io represent the circuit and socket represent the client

and this circuit can be coresponding to the server so server has a circuit

io and socket diagram : in the screenshot

Question 4

emit and on

Answer 4

emit - Used to send an event with some data and Can be used on both server and client. sending the data

eg - socket.emit(“eventName”, data);

socket.emit(“hello”,”namaste duniya”)

note: event name should be in “ “

on - Used to listen for an event. and Can be used on both server and client. receiving the data

eg - socket.on(“eventName”, callback function);

socket.on(“hello”,(msg)=>{
console.log(the message send by emit is ${msg});
})

Server listens with .on() and runs a callback

make sure the event name is same for both of them and callback function tells what task to perform when the event is triggered through emit

the data send by emit is revecied as parameter of callback function which can be later manipulated inside the function to perform task needed

when written io.emit or io.on then means we are triggering event or sending message to all the socket in the circuit(io)

whereas if you want to trigger event / send message to particular to one socket then socket.emit / socket.on

Question 5

broadcast , to , join

Answer 5

broadcast is the method used to send data to everyone except the socket that triggered the event

therefore - Broadcasting means sending a message to all connected clients except the one who sent it.

socket.broadcast.emit(“chatMessage”, msg);

.on() and broadcast are not used together.

.on(event, callback) → listens for an event.

.broadcast.emit(event, data) → sends an event to everyone except the sender.

They are used on opposite sides:

One socket emit or broadcast.emit → sends.

Other sockets use on → listen.