One method might be a self referencing ajax polling function something like...
(function getData() { setTimeout(function() {
$.ajax({
url: "locationofserver",
success: function(data){
// handle data returned (append chunks?)
// get next bit
getData();
},
dataType: "json"});
}, 20000);
})();
Where the first call returns information about the data length and how many chunks are available. This of course means the server needs to manage the breaking up of the data into chunks...
I would ask why you would need to chunk it though instead of just ensuring a persistent ajax connection until done? If you are truly looking to handle a data stream then maybe http://signalr.net/ or other push technology?