node.js setInterval doesn't work

Question

With node.js, I'm trying to send the current server_time to all clients in every second. Therefore, I wanted to use setInterval() to emit an event to all clients and sending the time, but it doesn't work. Did I define the setInterval function at the right place or did missed something else?

var http = require("http");
var socketIO = require('socket.io');
var connect = require('connect');

//keep track of every connected client
var clients = {};

//create Server 
var httpServer = connect.createServer(
    connect.static(__dirname)
).listen(8888);


//socket
var io = socketIO.listen(httpServer);
io.sockets.on('connection', function (socket) {

    //add current client id to array
    clients[socket.id] = socket;
    socket.on('close', function() {
        delete clients[socket.fd]; // remove the client.
    });

    //send news on connection to client
    socket.emit('news', { hello: 'world' }); 

    //this one works fine!
    //send server time on connection to client
    socket.emit("server_time", { time: new Date().toString() });

});

//this doesn't work!
// Write the time to all clients every second.
setInterval(function() { 
    var i, sock;
    for (i in clients) {
        sock = clients[i];
        if (sock.writable) { // in case it closed while we are iterating.
            sock.emit("server_time", {
                console.log("server_time sended");
                time: new Date().toString()

            });
        }
    }
}, 1000);       //every second

Answer 1

May I suggest a workaround/improvement that should fix the problem. Add the clients to a chat room. Somewhere in:

io.sockets.on('connection', function (socket) {

add a

socket.join('timer');

Then the setIntervall would be

setInterval(function() { 
    io.sockets.in('timer').emit("server_time", { time: new Date().toString() })
}, 1000); 

Hope this works for you!

Answer 2

The problem is the following function:

if (sock.writable) { // in case it closed while we are iterating.
  sock.emit("server_time", {
    // console.log("server_time sended"); // get rid of this line -> invalid code
    time: new Date().toString()
  });
}

sock.writable is undefined and therefore the emit event is never sent. Set the property to true on connection and to false on close.