node.js - socket.emit() vs. socket.send()

Question

What's the difference between these two?

I noticed that if I changed from socket.emit to socket.send in a working program, the server failed to receive the message, although I don't understand why.

I also noticed that in my program if I changed from socket.emit to socket.send, the server receives a message, but it seems to receive it multiple times. When I use console.log() to see what the server received, it shows something different from when I use socket.emit.

Why this behavior? How do you know when to use socket.emit or socket.send?

question from:https://stackoverflow.com/questions/65927308/what-is-the-difference-between-emit-and-send-in-flask-socketio

Answer 1

With socket.emit you can register custom event like that:

server:

var io = require('socket.io').listen(80);

io.sockets.on('connection', function (socket) {
  socket.emit('news', { hello: 'world' });
  socket.on('my other event', function (data) {
    console.log(data);
  });
});

client:

var socket = io.connect('http://localhost');
socket.on('news', function (data) {
  console.log(data);
  socket.emit('my other event', { my: 'data' });
});

Socket.send does the same, but you don't register to 'news' but to message:

server:

var io = require('socket.io').listen(80);

io.sockets.on('connection', function (socket) {
  socket.send('hi');
});

client:

var socket = io.connect('http://localhost');
socket.on('message', function (message) {
  console.log(message);
});