Create a list of Connected Clients using socket.io - node.js

Question

Here are 2 related questions. Posting them together makes more sense.
Question 1
I have a node.js app which emits an event out to all clients, and all current clients will respond with a ready emit. How can I create a list of all the clients that replied to the initial emit, and what kind of identification can be used to distinguish the clients?
Question2:
What I am trying to do after collect a list of connected clients, is to then access a MySQL database table of N number of rows and assign each client X rows each. These rows will be emitted back to their respective clients. How can this be done?
Current Code for Qn 1
Node Code
setInterval(function() {
util.log('Checking for new jobs...');
dbCheckQueue(function(results) { // checks if there are new rows to "distribute" to clients
if (results.length) {
util.log(results.length + ' new jobs found.');
io.sockets.emit('job_available');
}
});
}, 10*1000);
Client-side JS Code
socket.on('job_available', function() {
console.log('Job Available.. Responding with Ready!');
socket.emit('ready');
});
io.sockets.on('connection', function(socket) {
socket.on('ready', function() {
// UPDATE N rows with client_id in column checkout.
// Then SELECTS * from table where checkout = client_id
getListings(client_id, function(listings) {
socket.emit('job', listings); // send jobs
});
});
});
Current Code for Qn 2
The code works for a single client, but how do I loop through all connected clients and perform the same updating of column and selecting of rows?
io.sockets.on('connection', function(socket) {
socket.on('ready', function() {
// UPDATE N rows with client_id in column checkout.
// Then SELECTS * from table where checkout = client_id
getListings(client_id, function(listings) {
socket.emit('job', listings); // send jobs
});
});
});

Answer 1

Socket.io provides you with a public api for that, so instead of hacking something up like Bryan suggest you can use:
io.sockets.clients()
That will returns an array of all connected clients.
If you want all clients connected to a certain namespace:
io.of('/namespace').clients()
But you can even filter it even more.. if you want to have all sockets in a room:
io.sockets.clients('room name here as first argument')
Will return a array of connected sockets for the room room name here as first argument

Answer 2

You will need to keep track of the connected clients yourself. The simple way to do that would be to use an array:
var clients = [];
io.sockets.on('connect', function(client) {
clients.push(client);
client.on('disconnect', function() {
clients.splice(clients.indexOf(client), 1);
});
});
Then you can references that clients array on the server wherever you need to, in your ready event handler or whatever. Something like:
io.sockets.on('connection', function(socket) {
socket.on('ready', function() {
// UPDATE N rows with client_id in column checkout.
// Then SELECTS * from table where checkout = client_id
clients.forEach(function(client, index) {
var client_id = index; // Just use the index in the clients array for now
getListings(client_id, function(listings) {
socket.emit('job', listings); // send jobs
});
});
});
});