Signalk delta performance

var WebSocket = require('ws')

var url = "ws://" + "localhost:3000" + "/signalk/stream/v1?stream=delta";
var count = 0;

var connection = new WebSocket(url);
connection.onopen = function(msg) {
  console.log("open")
  var sub = '{"context":"vessels.self","subscribe":[{"path":"*"}]}';
  connection.send(sub);
};
connection.onerror = function(error) {
  console.log(error)
};
connection.onmessage = function(msg) {
  count++;
};

setInterval(function() {
  console.log(count);
  count = 0;
}, 1000)