Question

I have a basic Socket.io server setup like this:

var server = express.createServer().listen(port);
    this.io = socketIO.listen(server);

this.io.sockets.on('connection', function(socket){
        initSocket(socket);
    });

I also have socket.io configured to use XHR polling like so:

io.set("transports", ["xhr-polling"]);
io.set("close timeout", 3);
io.set("heartbeat interval", 2); 

The issue is every time the client sends a heartbeat (every 2 sec), the ‘connection’ event is being fired. Is there a different event I can use that will fire once each time a socket initially connects?

I would use the “authorization” event, but that only passes in a handshake object not the actual socket.

Answer 1

Found the problem. I had my xhr “polling duration” set to heroku’s suggested 10s like so:

io.set("polling duration", 10);

Which means that the client only makes a new xhr request every 10 seconds (as soon as the previous request returns). At the same time I had the “close timeout” set to 3 seconds:

io.set("close timeout", 3);

Which means if the server does not hear from the client within 3 seconds since its last request it closes the connection, hence the continuous ‘disconnect/connection’ events being fired.

The solution was to set the close timeout higher than the polling duration. It would seem that the “heartbeat interval” is not relevant for xhr connections.