I am using the "ws" NodeJS websocket library. Previously I was trying out socket.io; with socket.io I could implement callbacks between the client and server like this:
socket.emit('Data', data, function(data){
console.log(data);
});
socket.on('Data', function(data, callback){
callback('it worked');
});
I have tried to do the same thing using the ws library, but have not had any success. Is it possible, and if so how?
The API is pretty similar and you can do pretty much the same things.
For example on the server side instead of:
s.emit('message', 'message from server');
you use:
s.send('message from server', ()=>{});
To receive it on the client side instead of:
s.on('message', function (m) {
// ...
});
you use:
s.addEventListener('message', function (m) {
// ...
});
And so on.
In this answer I showed example code (both frontend and backend) to demonstrate the difference between Socket.io and WebSocket:
This is example server code:
var path = require('path');
var app = require('express')();
var ws = require('express-ws')(app);
app.get('/', (req, res) => {
console.error('express connection');
res.sendFile(path.join(__dirname, 'ws.html'));
});
app.ws('/', (s, req) => {
console.error('websocket connection');
for (var t = 0; t < 3; t++)
setTimeout(() => s.send('message from server', ()=>{}), 1000*t);
});
app.listen(3001, () => console.error('listening on http://localhost:3001/'));
console.error('websocket example');
Example browser code:
var l = document.getElementById('l');
var log = function (m) {
var i = document.createElement('li');
i.innerText = new Date().toISOString()+' '+m;
l.appendChild(i);
}
log('opening websocket connection');
var s = new WebSocket('ws://'+window.location.host+'/');
s.addEventListener('error', function (m) { log("error"); });
s.addEventListener('open', function (m) { log("websocket connection open"); });
s.addEventListener('message', function (m) { log(m.data); });
See this for more info.
This can be done with WebSockets-Callback like this
wscb.send({cmd: 'Hello server!'},
function(response){
//do something...
}
)
