1.0.7 • Public • Published

Stream module for Socket.IO

This library is an update to the socket.io-stream node module. No code changes have been made, but the debug module has been updated to avoid a security vulnerability in the existing project.

REUSE status


  • node.js 4.x or higher

Download and installation

npm install @sap_oss/node-socketio-stream

Known issues

Issues on the original socket.io-stream module (listed here) also apply to this module.

How to obtain support

This project is provided as-is. No new features or bug fixes are anticipated.


Copyright 2020-2023 SAP SE or an SAP affiliate company and node-socketio-stream contributors. See also the LICENSE file.


If you are not familiar with Stream API, be sure to check out the docs. I also recommend checking out the awesome Stream Handbook.

For streaming between server and client, you will send stream instances first. To receive streams, you just wrap socket with node-socketio-stream, then listen any events as usual.


var io = require('socket.io').listen(80);
var ss = require('@sap_oss/node-socketio-stream');
var path = require('path');

io.of('/user').on('connection', function(socket) {
  ss(socket).on('profile-image', function(stream, data) {
    var filename = path.basename(data.name);

createStream() returns a new stream which can be sent by emit().


var io = require('socket.io-client');
var ss = require('@sap_oss/node-socketio-stream');

var socket = io.connect('http://example.com/user');
var stream = ss.createStream();
var filename = 'profile.jpg';

ss(socket).emit('profile-image', stream, {name: filename});

You can stream data from a client to server, and vice versa.

// send data
ss(socket).on('file', function(stream) {

// receive data
ss(socket).emit('file', stream);


This module can be used on the browser. To do so, just copy a file to a public directory.

$ cp node_modules/@sap_oss/node-socketio-stream/node-socketio-stream.js somewhere/public/

You can also use browserify to create your own bundle.

$ npm install browserify -g
$ cd node_modules/@sap_oss/node-socketio-stream
$ browserify index.js -s ss > node-socketio-stream.js
<input id="file" type="file" />

<script src="/socket.io/socket.io.js"></script>
<script src="/js/node-socketio-stream.js"></script>
<script src="/js/jquery.js"></script>
$(function() {
  var socket = io.connect('/foo');

  $('#file').change(function(e) {
    var file = e.target.files[0];
    var stream = ss.createStream();

    // upload a file to the server.
    ss(socket).emit('file', stream, {size: file.size});

Upload progress

You can track upload progress like the following:

var blobStream = ss.createBlobReadStream(file);
var size = 0;

blobStream.on('data', function(chunk) {
  size += chunk.length;
  console.log(Math.floor(size / file.size * 100) + '%');
  // -> e.g. '42%'


Socket.IO v0.9 support

You have to set forceBase64 option true when using the library with socket.io v0.9.x.

ss.forceBase64 = true;



  • sio socket.io Socket A socket of Socket.IO, both for client and server
  • return Socket

Look up an existing Socket instance based on sio (a socket of Socket.IO), or create one if it doesn't exist.

socket.emit(event, [arg1], [arg2], [...])

  • event String The event name

Emit an event with variable number of arguments including at least a stream.

ss(socket).emit('myevent', stream, {name: 'thefilename'}, function() { ... });

// send some streams at a time.
ss(socket).emit('multiple-streams', stream1, stream2);

// as members of array or object.
ss(socket).emit('flexible', [stream1, { foo: stream2 }]);

// get streams through the ack callback
ss(socket).emit('ack', function(stream1, stream2) { ... });

socket.on(event, listener)

  • event String The event name
  • listener Function The event handler function

Add a listener for event. listener will take stream(s) with any data as arguments.

ss(socket).on('myevent', function(stream, data, callback) { ... });

// access stream options
ss(socket).on('foo', function(stream) {
  if (stream.options && stream.options.highWaterMark > 1024) {
    console.error('Too big highWaterMark.');


  • options Object
    • highWaterMark Number
    • encoding String
    • decodeStrings Boolean
    • objectMode Boolean
    • allowHalfOpen Boolean if true, then the stream won't automatically close when the other endpoint ends. Default to false.
  • return Duplex Stream

Create a new duplex stream. See the docs for the details of stream and options.

var stream = ss.createStream();

// with options
var stream = ss.createStream({
  highWaterMark: 1024,
  objectMode: true,
  allowHalfOpen: true

ss.createBlobReadStream(blob, [options])

  • options Object
    • highWaterMark Number
    • encoding String
    • objectMode Boolean
  • return Readable Stream

Create a new readable stream for Blob and File on browser. See the docs for the details of stream and options.

var stream = ss.createBlobReadStream(new Blob([1, 2, 3]));


Node Buffer class to use on browser, which is exposed for convenience. On Node environment, you should just use normal Buffer.

var stream = ss.createStream();
stream.write(new ss.Buffer([0, 1, 2]));

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