Socket.io re-authorization

You should be able to do that by enabling the socket.io authorization. Once enabled it will call into the provided function when socket.io connects.

Here is some code I used a while ago that should get you started.

var connect = require('connect');

// these should be the same as you use for setting the cookie
var sessionKey = "yourSessionKey"; 
var sessionSecret = "yourSessionSecret";

socketIO.set('authorization', function (data, accept) {
    // check if there's a cookie header
    if (data.headers.cookie) {
        // if there is, parse the cookie
        data.cookie = connect.utils.parseSignedCookies(cookie.parse(decodeURIComponent(data.headers.cookie)), sessionSecret);
        if (!data.cookie[sessionKey]) return accept('No cookie value for session key ' + sessionKey, false);
        var parts = data.cookie[sessionKey].split('.');
        data.sessionId = parts[0];

        // at this point you would check if the user has been authenticated 
        // by using the session id as key. You could store such a reference
        // in redis after the user logged in for example.

        // you might want to set the userid on `data` so that it is accessible
        // through the `socket.handshake` object later on
        data.userid = username;

        // accept the incoming connection
        return accept(null, true);
    } else {
       // if there isn't, turn down the connection with a message
       // and leave the function.
       return accept('No cookie transmitted.', false);
    }
});

Once you set the data properties (e.g. data.userid in the above example) you can access them by via the socket.handshake object. For example:

io.sockets.on('connection', function (socket) {
    var userId = socket.handshake.userid;

    socket.on('reauthorize-user', function(){
         // check the user status using the userId then emit a socket event back
         // to the client with the result
         socket.emit('reauthorization-result', isAuthorized);
    });
});

On the client you would just emit the reauthorize-user event and listen to the reauthorization-result event. You could obviously have a setTimeout to perform the check in certain intervals.