Using node and express, the below works just fine.
var app = express();
app.listen(app.get('port'), function() {
});
I assume that a server is created implicitly in the above construct.
When adding socket.io, I've seen the following being done.
var app = express();
var server = http.createServer(app);
var io = require('socket.io').listen(server);
app.listen(app.get('port'), function() {
});
What is the need for explicitly adding http.createServer(app) ? Won't the creation of an additional server mess up things ? Or put it other way, is it ok to create many more http.createServer(app) ?
In either case, only one server is created. When using socket.io, you share the same http server between socket.io and express. Both libraries attach event listeners to the same server and have a chance to respond to the same events. They cooperate nicely because socket.io only handles relevant requests and express handles all the non-websocket requests. And just FYI you could not create more than one server on the same port. Only one process can listen on a TCP port at a time in the OS, so the second one would fail with an error when attempting to bind an in-use port.