node js server: issue passing a variable to a function

I am building my first node.js server to perform a mysql query and return results from the database. Everything works but now I cannot find the right way to pass a value from the url (query section) to the function that performs the query (the PollingLoop function). No problems to retrieve the url and to get the parameter in the handler function but to move it to pollingLoop I have tried almost all I know about javascript (not enough I see). This is my code now that fails to run because of the reference error in pollingLoop for hwkey that is not defined.

var app = require('http').createServer(handler),
  io = require('socket.io').listen(app),
  url = require('url'),
  fs = require('fs'),
  mysql = require('mysql'),
  connectionsArray = [],
  connection = mysql.createConnection({
    host: 'localhost',
    user: 'root',
    password: 'flipper',
    database: 'oclock',
    port: 3306
  }),
  POLLING_INTERVAL = 3000,
  pollingTimer;

// If there is an error connecting to the database
connection.connect(function(err) {
  // connected! (unless `err` is set)
  if (err) {
    console.log(err);
  }
});

// creating the server ( localhost:8000 )
app.listen(8000);


function handler(req, res) {

    console.log("INCOMING REQUEST: "+req.method+" "+req.url);
    req.parsed_url = url.parse(req.url, true);
    var getp = req.parsed_url.query;
    var hwkey = getp.hk;
    console.log(hwkey);

    fs.readFile(__dirname + '/client.html', function(err, data) {
    if (err) {
      console.log(err);
      res.writeHead(500);
      return res.end('Error loading client.html');
    }
    res.writeHead(200);
    res.end(data);
  });
}


function pollingLoop(){
  // Doing the database query
  var query = connection.query('SELECT max(id), testo, created_by FROM flashmsgs WHERE hwk="'+hwkey+'"'),
  //var query = connection.query('SELECT max(id), testo, created_by FROM flashmsgs'),
    flashmsgs = []; // this array will contain the result of our db query

  // setting the query listeners
  query
    .on('error', function(err) {
      // Handle error, and 'end' event will be emitted after this as well
      console.log(err);
      updateSockets(err);
    })
    .on('result', function(flashmsg) {
      // it fills our array looping on each user row inside the db
      flashmsgs.push(flashmsg);
    })
    .on('end', function() {
      // loop on itself only if there are sockets still connected
      if (connectionsArray.length) {

        pollingTimer = setTimeout(pollingLoop, POLLING_INTERVAL);

        updateSockets({
          flashmsgs: flashmsgs
        });
      } else {

        console.log('The server timer was stopped because there are no more socket connections on the app')

      }
    });
};


// creating a new websocket to keep the content updated without any AJAX request
io.sockets.on('connection', function(socket) {

  console.log('Number of connections:' + connectionsArray.length);
  // starting the loop only if at least there is one user connected
  if (!connectionsArray.length) {
    pollingLoop();
  }

  socket.on('disconnect', function() {
    var socketIndex = connectionsArray.indexOf(socket);
    console.log('socketID = %s got disconnected', socketIndex);
    if (~socketIndex) {
      connectionsArray.splice(socketIndex, 1);
    }
  });

  console.log('A new socket is connected!');
  connectionsArray.push(socket);

});

var updateSockets = function(data) {
  // adding the time of the last update
  data.time = new Date();
  console.log('Pushing new data to the clients connected ( connections amount = %s ) - %s', connectionsArray.length , data.time);
  // sending new data to all the sockets connected
  connectionsArray.forEach(function(tmpSocket) {
    tmpSocket.volatile.emit('notification', data);
  });
};

console.log('Please use your browser to navigate to http://localhost:8000');