sse/lib/sseclient.js

The HTML5 Server-Sent events specification is introduced "to enable servers to push data to Web pages over HTTP or using dedicated server-push protocols".

var util    = require('util'),
    events  = require('events');

module.exports = SSEClient;

function SSEClient(req, res) {
  this.req = req;
  this.res = res;
  var self = this;
  res.on('close', function() {
    self.emit('close');
  });
}

util.inherits(SSEClient, events.EventEmitter);

SSEClient.prototype.initialize = function() {
  this.req.socket.setNoDelay(true);
  this.res.writeHead(200, {
    'Content-Type': 'text/event-stream',
    'Cache-Control': 'no-cache, no-transform',
    'Connection': 'keep-alive'
  });
  this.res.write(':ok\n\n');
};

SSEClient.prototype.send = function(event, data, id) {
  if (arguments.length === 0) return;

  var senderObject = {
    event : event || undefined,
    data  : data || undefined,
    id    : id || undefined,
    retry : undefined
  };

  if (typeof event == 'object') {
    senderObject.event   = event.event || undefined,
    senderObject.data    = event.data || undefined,
    senderObject.id      = event.id || undefined,
    senderObject.retry   = event.retry || undefined
  }

  if (typeof event != 'object' && arguments.length === 1) {
    senderObject.event   = undefined;
    senderObject.data    = event;
  }

  if (senderObject.event) this.res.write('event: ' + senderObject.event + '\n');
  if (senderObject.retry) this.res.write('retry: ' + senderObject.retry + '\n');
  if (senderObject.id) this.res.write('id: ' + senderObject.id + '\n');

  senderObject.data = senderObject.data.replace(/(\r\n|\r|\n)/g, '\n');
  var dataLines = senderObject.data.split(/\n/);

  for (var i = 0, l = dataLines.length; i < l; ++i) {
    var line = dataLines[i];
    if ((i+1) === l) this.res.write('data: ' + line + '\n\n');
    else this.res.write('data: ' + line + '\n');
  }
}

SSEClient.prototype.close = function() {
  this.res.end();
}