Node.js Server-Sent Events with Total.js framework

With the Total.js framework, you can create an HTTP route for Server-Sent Events, or you can connect easily to another server with implemented Server-Sent Events.

Server-side implementation:

exports.install = function() {
  ROUTE('GET /sse/', serversentevents, ['sse']);
 };
 function serversentevents() {
  var self = this;
  var lasteventid = self.sseID || '0';
  var counter = U.parseInt(lasteventid);
  var indexer = 0; var interval = setInterval(function() {
  // Closes client after 10 seconds
  if (indexer++ > 10) {
  self.close();
  clearInterval(interval);
  } else {
  // Sends data to the client
  if (!self.sse({ counter: counter++, message: GUID() }, null, counter)) {
  // Something wrong
  // Client closed
  clearInterval(interval);
  }
  } }, 1000);
 }

Client-side (web browser) implementation:

var sse = new EventSource('/sse/');
 sse.onmessage = function(ev)
 {
  // A message
  console.log('Message:', ev.data);
 };
 sse.onerror = function(e) {
  // Some error
  console.log('Error:', e);
 };

With the Total.js framework is very easy to handle messages from another server with implemented Server-Sent Events functionality. For example, the code below captures messages from another HTTP server:

var opt = {};
 opt.url = 'http://127.0.0.1:8000/sse/';
 opt.custom = true;
 opt.headers = { accept: 'text/event-stream' };
 opt.timeout = 0;
 opt.callback = function(err, response)
 {
  response.stream.on('data', U.streamer('\n\n', function(chunk)
  {
  var lines = chunk.toString('utf8').split('\n');
  var msg = {}; // Server sent events parser
  for (var line of lines) {
  var index = line ? line.indexOf(':') : -1;
  if (index !== -1) {
  var key = line.substring(0, index);
  var val = line.substring(index + 2);
  switch (key) {
  case 'data':
  val = val.parseJSON();
  break;
  case 'retry':
  val = +val;
  break;
  }
  msg[key] = val;
  }
  }
  // msg.id {String}
  // msg.data {Object}
  // msg.retry {Number}
  // msg.event {String}
 
  console.log(msg);
  }));
 };
 
 REQUEST(opt);

Source: Medium - Peter Širka

The Tech Platform

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