server.js

//Including Web server
var web = require("./server/web.js");
//Starting server on Port 8080
web.start(8080);

//Main logic
//
var socket;
//server needs to store whiteboards and content
var rooms = [];
//room id used to distinguish rooms
var roomIds = {};

function getRoom(roomId)
{
    if (!(roomId in roomIds))
    {
        roomIds[roomId] = rooms.length;
        rooms.push([]);
    }
    return rooms[roomIds[roomId]];
}

function sendRoom(roomId)
{
    web.io.emit("servermessage", {
        "room": roomId,
        "command": "send_room",
        "data": getRoom(roomId)
    });
}

function draw(msg)
{
    var room = getRoom(msg["room"]);
    room.push(msg["data"]);
    web.io.emit("servermessage", {
        "room": msg["room"],
        "command": "draw",
        "data": msg["data"]
    });
}

function clear(msg)
{
    var room = getRoom(msg["room"]);
    while (room.length) room.pop();

    web.io.emit("servermessage", {
        "room": msg["room"],
        "command": "clear"
    });
}

function join(msg)
{
    console.log("Client wants to join " + msg["room"]);
    sendRoom(msg["room"]);
}

function handleMessage(msg)
{
    try
    {
        //check if message is valid
        if (!("room" in msg &&
            "command" in msg))
            return;

        if (msg["command"] == "draw") draw(msg);
        if (msg["command"] == "join") join(msg);
        if (msg["command"] == "clear") clear(msg);
    }
    catch (err)
    {
        console.log(err);
    }
}

web.io.on('connection', function (socket) {
    console.log((new Date()) + ' Connection established.');
    socket.on("message", handleMessage);
});