How to consistently transfer a lot of data through the Socket.io?

From the server side is the SQL query, the result is a lot of data. On average 15K lines. After this piece of rows sorted by date, where the date the array key and value of each - the list of objects on that date. I.e. something like:

points[row.time_update] = [ {val1: 1, val2: 123, val6:321}, {val1: 21, val2: 777, val6:2} ... ]

I.e., the solution to the problem via a limit\offset I channel. What's the problem:

on the client side, the code hangs (the code is rough everywhere, but it reflects the essence):

socket.on('update_recv', function(data) { 
console.log(data);
});

server hangs like this:

socket.on('update', function(data){ 
 knex(sql .... ).then(function(rows){
 // processed line, collect the points array in the required format. 

 var keys = Object.keys(points); // need to issue a batch by date
 for( var k in keys )
{
 // here begins my unknown magic. If bryaknut after socket.emit
 // the data arrives. ie 1 time. otherwise, the cycle goes on, but the front
 // nothing comes. 
 socket.emit('update_recv', {result: JSON.stringify(points[keys[k]]) })
 sleep.sleep(3); // need delay until the rough
}
});
});

How do I sequentially with time intervals, transfer a bunch of lines to the front? To transfer one "packet" with subsequent treatment there, is not very reasonable, plus still is not transmitted.