Websockets-NodeJS. Is it possible to broadcast a message to all connected clients(from the server) without having a client message the client first

With NodeJS and websockets, I am trying to implement an online game server, for a multiplier game, I have people moving around with the ability to see each other, but when the server spawns a new enemy, I want to be able to broadcast the message to all connected clients.

But without the clients messaging the server first.

For example - The game spawns an enemy, send information to all clients.

My code so far:

/**************************************************
** NODE.JS REQUIREMENTS
**************************************************/

var util = require("util"),                 
// Utility resources (logging, object inspection, etc)

    io = require("socket.io"),              
// Socket.IO

    Player = require("./Player").Player,    // Player class
    Zombie = require("./Zombie").Zombie;

// Socket controller

var socket, 

// Array of connected players   

    players,

    zombies;

var level = 1,
    score = 0,
    levelling = false;



function init() {
    // Create an empty array to store players

    players = [];

    zombies = [];

    // Set up Socket.IO to listen on port 8000

    socket = io.listen(8000);

    // Configure Socket.IO

    socket.configure(function() {
        // Only use WebSockets

        socket.set("transports", ["websocket"]);


        // Restrict log output

        socket.set("log level", 2);
    });

    // Start listening for events

    setEventHandlers();
};

blah blah blah -- tl;dr -- Game loop:

function mainLoop(){

//Main loop for the server. Called 60 times a second. May be modified for game  
     speed.
//setTimeout(mainLoop, 1000/5000);

this.broadcast.emit("update"); 

    //THIS broadcast.emit line is where the error is being thrown. I need to know how   
    to broadcast here without the client initializing first.
};

I have tried a few things, socket.broadcast.emit("update");, but with no success.

I have tried for looping through currently known users and using "this.emit" but I always get "cannot call method emit of undefined" so damn annoying.

but when I have the clients send a message first, for example, when the client moves, it sends some information to the server, the server reacts with:

 function onSocketConnection(client) {
        util.log("New player has connected: " + client.id);

        // Listen for client disconnected

        client.on("disconnect", onClientDisconnect);

        // Listen for new player message

        client.on("new player", onNewPlayer);

        // Listen for move player message

        client.on("move player", onMovePlayer);

        //listen for deaths

        client.on("death", onPlayerDeath);

        //listen for not moved message, to stop sprite animation

        client.on("not moved", notMoved);
    };

    // Player has moved

    function onMovePlayer(data) {
        // Find player in array

        var movePlayer = playerById(this.id);

        // Player not found

        if (!movePlayer) {
            util.log("Player not found: "+this.id + " when asking if moved");
            return;
        };

        // Update player position
        movePlayer.setX(data.x);
        movePlayer.setY(data.y);
        movePlayer.setDir(data.dir);

        // Broadcast updated position to connected socket clients

        this.broadcast.emit("move player", {id: movePlayer.id, x:
            movePlayer.getX(), y:movePlayer.getY(), dir: movePlayer.getDir()});
    };

AND THEN the "this.broadcast.emit" has no issues. Without throwing the error.