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SSE (Server Sent Events) library for node.js.

sselib is a implementation of the server-side part of the [SSE] 1 protocol written in Coffee Script for the node.js platform.

Build Status NPM version


Install with npm:

$ npm install sselib


None, tested on node.js 0.6 >

Connect and Express Middleware

sselib can be used as a middleware for applications following the Connect convention.



    var sselib = require('sselib'),
    express = require('express');
    var app = express();
    app.get('/events', function(req, res) {
        event: 'update',
        data: 'I am a stray cat.'


    sselib = require 'sselib'
    express = require 'express'
    app = express()
    app.use sselib.middleware()
    app.get '/events'(req, res) ->
        event: 'update'
        data: 'I am a stray cat.'


You can pass options when initializing the middleware.

      retry: 5*1000,
      keepAlive: 15*1000,
      compatibility: true

A already initialized connection can use res.sse.set in order to set a new value for the option. Setting longer retry values and closing connections can be a effective strategy when servers are under high load.

    app.get('/events', function(req, res) {
      res.sse.set('retry', 30*1000);

res.sse.get(option) respectively gets the current configuration.


The time in milliseconds for client reconnects. Default is 5 seconds.
Set to false in order to disable.


Sends pseudo keep alive heartbeats in order to keep the connection open. The value is the amount of milliseconds between each keepAlive heartbeat. Default is 15 seconds.
Set to false in order to disable.


"Quirks mode". Adds support for some polyfills and the way MSIE handles XDomainRequest. Default is true
Set to false in order to disable.

Use as a library to serialize data for your own transmission


    var sselib = require('sselib');
    console.log(sselib.event("notice")); // "event: notice\n" 
    console.log("Hello there!")); // "data: Hello there!\n\n" 
    // or: "Hello there!", function(err, result) {
      if (err) {
        // print the error to console 
      console.log(result) // "data: Hello there!\n\n" 


sselib.comment(comment [, callback])

Returns a SSE-serialized comment string representing a comment (please note that comments are invisible to browser clients).

sselib.event(event [, callback])

Returns a SSE-serialized event string that can be used with a following data type to trigger a event in the browser. [, callback])

Returns a SSE-serialized id string. If called without id it will use a UNIX timestamp as the id. [, callback])

Returns a SSE-serialized data string.

sselib.message(obj [, callback])

message is provided as a meta-serializer. It will return a SSE-serialized string from a message object you pass in.


Returns a Object containing valid HTTP-headers suitable for a http.ServerResponse.


Message Object

sselib.message() graph

A message object is simply a javascript object containing the data and event keys, it can also optionally be given a id key.


{event: 'update', data: 'I am a stray cat.', id: 789}


BSD (see

Made by massförströelse