engine.io-parser

What is engine.io-parser?

The engine.io-parser npm package is designed for encoding and decoding packets used by engine.io, which is a transport layer for real-time data exchange between a client and a server. It handles the framing of messages for transport over various real-time protocols and supports binary data.

What are engine.io-parser's main functionalities?

Encoding messages

This feature allows you to encode a message packet into a format suitable for transport over the network. The `encodePacket` function takes a packet object and a callback function that receives the encoded packet.

const { encodePacket } = require('engine.io-parser');
const packet = { type: 'message', data: 'hello' };
encodePacket(packet, false, (encodedPacket) => {
  // handle the encoded packet
});

Decoding messages

This feature allows you to decode a message packet that was received from the network. The `decodePacket` function takes an encoded packet and the type of data ('string' or 'binary') and returns the decoded packet object.

const { decodePacket } = require('engine.io-parser');
const encodedPacket = '2hello'; // example of an encoded message packet
const packet = decodePacket(encodedPacket, 'string');
// handle the decoded packet

Support for binary data

This feature provides support for encoding and decoding binary data. The `encodePacket` and `decodePacket` functions can handle binary data when the second argument is set to `true` for binary.

const { encodePacket, decodePacket } = require('engine.io-parser');
const binaryData = new ArrayBuffer(100);
const packet = { type: 'message', data: binaryData };
encodePacket(packet, true, (encodedPacket) => {
  // handle the encoded packet with binary data
});
const decodedPacket = decodePacket(encodedPacket, 'binary');
// handle the decoded packet with binary data

Other packages similar to engine.io-parser

ws

The 'ws' package provides a WebSocket client and server implementation. It allows for real-time communication similar to engine.io-parser but is focused on the WebSocket protocol specifically, whereas engine.io-parser is part of the engine.io ecosystem which can fall back to other transport mechanisms if WebSockets are not available.

socket.io-parser

The 'socket.io-parser' is used by Socket.IO to encode and decode messages. It is similar to engine.io-parser but is tailored for the Socket.IO framework, which builds on top of engine.io to provide additional features like rooms, namespaces, and middleware support.

json-socket

The 'json-socket' package is a wrapper around the Node.js net library that adds a layer for seamless JSON message sending. It is similar to engine.io-parser in that it handles message framing, but it is specifically designed for TCP sockets and does not support the variety of transport layers that engine.io-parser does.

README

engine.io-parser

This is the JavaScript parser for the engine.io protocol encoding, shared by both engine.io-client and engine.io.

How to use

Standalone

The parser can encode/decode packets, payloads, and payloads as binary with the following methods: encodePacket, decodePacket, encodePayload, decodePayload.

Example:

const parser = require("engine.io-parser");
const data = Buffer.from([ 1, 2, 3, 4 ]);

parser.encodePacket({ type: "message", data }, encoded => {
  const decodedData = parser.decodePacket(encoded); // decodedData === data
});

With browserify

Engine.IO Parser is a commonjs module, which means you can include it by using require on the browser and package using browserify:

1. install the parser package

   npm install engine.io-parser
   

2. write your app code

   const parser = require("engine.io-parser");
   
   const testBuffer = new Int8Array(10);
   for (let i = 0; i < testBuffer.length; i++) testBuffer[i] = i;
   
   const packets = [{ type: "message", data: testBuffer.buffer }, { type: "message", data: "hello" }];
   
   parser.encodePayload(packets, encoded => {
     parser.decodePayload(encoded,
       (packet, index, total) => {
         const isLast = index + 1 == total;
         if (!isLast) {
           const buffer = new Int8Array(packet.data); // testBuffer
         } else {
           const message = packet.data; // "hello"
         }
       });
   });
   

3. build your app bundle

   $ browserify app.js > bundle.js
   

4. include on your page

   <script src="/path/to/bundle.js"></script>
   

Features

• Runs on browser and node.js seamlessly
• Runs inside HTML5 WebWorker
• Can encode and decode packets
  • Encodes from/to ArrayBuffer or Blob when in browser, and Buffer or ArrayBuffer in Node

API

Note: cb(type) means the type is a callback function that contains a parameter of type type when called.

Node

• encodePacket

  • Encodes a packet.
  • Parameters
    • Object: the packet to encode, has type and data.
      • data: can be a String, Number, Buffer, ArrayBuffer
    • Boolean: binary support
    • Function: callback, returns the encoded packet (cb(String))

• decodePacket

  • Decodes a packet. Data also available as an ArrayBuffer if requested.
  • Returns data as String or (Blob on browser, ArrayBuffer on Node)
  • Parameters
    • String | ArrayBuffer: the packet to decode, has type and data
    • String: optional, the binary type

• encodePayload

  • Encodes multiple messages (payload).
  • If any contents are binary, they will be encoded as base64 strings. Base64 encoded strings are marked with a b before the length specifier
  • Parameters
    • Array: an array of packets
    • Function: callback, returns the encoded payload (cb(String))

• decodePayload

  • Decodes data when a payload is maybe expected. Possible binary contents are decoded from their base64 representation.
  • Parameters
    • String: the payload
    • Function: callback, returns (cb(Object: packet, Number:packet index, Number:packet total))

Tests

Standalone tests can be run with npm test which will run the node.js tests.

Browser tests are run using zuul. (You must have zuul setup with a saucelabs account.)

You can run the tests locally using the following command:

npm run test:browser

Support

The support channels for engine.io-parser are the same as socket.io:

• irc.freenode.net #socket.io
• Github Discussions
• Website

Development

To contribute patches, run tests or benchmarks, make sure to clone the repository:

git clone git://github.com/socketio/engine.io-parser.git

Then:

cd engine.io-parser
npm ci

See the Tests section above for how to run tests before submitting any patches.

License

MIT