No tutorial needed. The Socket.IO FAQ is pretty straightforward on this one:
socket.emit('news', { hello: 'world' });
EDIT: Folks are linking to this question when asking about how to get that socket object later. There is no need to. When a new client connects, save a reference to that socket on whatever object you’re keeping your user information on. My comment from below:
In the top of your script somewhere, setup an object to hold your users’ information.
var connectedUsers = {};In your
.on('connection')function, add that socket to your new object.connectedUsers[USER_NAME_HERE] = socket;Then you can easily retrieve it later.connectedUsers[USER_NAME_HERE].emit('something', 'something');