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

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
            });
        });
    });
});