merge socket.io and express.js sessions

I want to merge express.js and socket.io sessions together. Below is my code (socket.io part)

var io = require('socket.io').listen(app);
io.set('log level', 1);

io.sockets.on('connection', function (socket) {
    console.log('client connected');
client.send(client.id);//send client id to client itself
socket.on('connect', function(){
    console.log(socket.id + ' connected');
});
socket.on('disconnect', function(){
    console.log(socket.id + ' disconnected');
});
});

My express.js Session settings:

app.configure(function() {
  //app.use(express.logger());
  app.use(express.bodyParser());
  app.use(express.methodOverride());
  app.use(express.static(__dirname + '/static'));
  app.use(express.cookieParser());
  app.use(express.session({store: MemStore({
    reapInterval: 60000 * 10
  }), secret:'foobar', key: 'express.sid'
}));

My main problem is in my terminal when user travels from one url to another, the session id changes also: But I don't want it to be changed.

info  - socket.io started
client connected
client connected
4Z0bYHzfWCEFzbbe4WUK disconnected
e_uSvxhSLbLAC9-F4WUL disconnected
client connected
bKDy90gsrWWTRJDD4WUM disconnected
client connected
RJ5qqCL2wfmXbd7U4WUN disconnected
client connected
wjN5Sqx4rucRtWL_4WUO disconnected