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
?
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);
});
TL;DR:
socket.send(data, callback)
is essentially equivalent to calling socket.emit('message', JSON.stringify(data), callback)
Without looking at the source code, I would assume that the send function is more efficient edit: for sending string messages, at least?
So yeah basically emit allows you to send objects, which is very handy.
Take this example with socket.emit
:
sendMessage: function(type, message) {
socket.emit('message', {
type: type,
message: message
});
}
and for those keeping score at home, here is what it looks like using socket.send
:
sendMessage: function(type, message) {
socket.send(JSON.stringify({
type: type,
message: message
}));
}
Simple and precise (Source: Socket.IO google group):
socket.emit
allows you to emit custom events on the server and client
socket.send
sends messages which are received with the 'message'
event
In basic two way communication systems, socket.emit has proved to be more convincing and easy to use (personal experience) and is a part of Socket.IO which is primarily built for such purposes
https://socket.io/docs/client-api/#socket-send-args-ack
socket.send
// Sends a message event
socket.emit(eventName[, ...args][, ack])
// you can custom eventName
socket.send
is implemented for compatibility with vanilla WebSocket interface. socket.emit
is feature of Socket.IO only. They both do the same, but socket.emit
is a bit more convenient in handling messages.
Source: Stackoverflow.com