What is engine.io-client?
The engine.io-client npm package is a client-side library that provides bidirectional event-based communication between web clients and servers. It is the client component of the Engine.IO protocol, which is a transport layer built on top of WebSocket and other transport mechanisms to provide a reliable, low-latency connection for real-time applications.
What are engine.io-client's main functionalities?
Establishing a connection
This feature allows you to establish a connection to an Engine.IO server. The 'open' event is emitted when the connection is successfully established.
const eio = require('engine.io-client');
const socket = eio('ws://localhost');
socket.on('open', function(){
console.log('Connection established');
});
Sending messages
Once a connection is established, you can send messages to the server using the 'send' method.
socket.send('Hello World!');
Receiving messages
You can listen for messages from the server with the 'message' event. The callback function receives the message data as its argument.
socket.on('message', function(data){
console.log('Received message:', data);
});
Handling connection errors
The 'error' event is emitted when there is a connection error. The callback function receives the error object as its argument.
socket.on('error', function(error){
console.error('Connection error:', error);
});
Closing the connection
The 'close' event is emitted when the connection is closed. The callback function receives the reason and a description as arguments.
socket.on('close', function(reason, description){
console.log('Connection closed', reason, description);
});
Other packages similar to engine.io-client
socket.io-client
Socket.IO-client is a more feature-rich client-side library that provides real-time bidirectional event-based communication, similar to engine.io-client. It is built on top of engine.io-client and adds additional features like namespaces, rooms, and automatic reconnection.
ws
The 'ws' package is a simple WebSocket client and server implementation for Node.js. Unlike engine.io-client, it does not provide built-in mechanisms for features like automatic reconnection and binary data handling, but it allows for more control over the WebSocket connection.
faye-websocket
Faye-websocket is a WebSocket client and server for Node.js and Ruby. It provides a simple API for handling WebSocket connections but does not include the higher-level abstractions and fallback mechanisms that engine.io-client offers.
Engine.IO client
This is the client for Engine, the
implementation of transport-based cross-browser/cross-device bi-directional
communication layer for Socket.IO.
Hello World
<script src="/path/to/engine.js"></script>
<script>
var socket = new eio.Socket({ host: 'localhost', port: 80 });
socket.onopen = function () {
socket.onmessage = function (data) { });
socket.onclose = function () { });
};
</script>
Features
- Lightweight
- Lazyloads Flash transport
- Isomorphic with WebSocket API
- Written for node, runs on browser thanks to
browserbuild
- Maximizes code readability / maintenance.
- Simplifies testing.
- Transports are independent of
Engine
- Easy to debug
- Easy to unit test
- Runs inside HTML5 WebWorker
API
Top-level
These are exposed in the eio
global namespace (in the browser), or by
require('engine.io-client')
(in Node.JS).
Properties
version
(String): client versionprotocol
(Number): protocol revision numberSocket
(Function): client constructor
Socket
The client class. Inherits from EventEmitter.
Properties
onopen
(Function)
onmessage
(Function)
onclose
(Function)
Events
open
- Fired upon successful connection.
message
- Fired when data is received from the server.
- Arguments
String
: utf-8 encoded data
close
- Fired upon disconnection.
error
- Fired when an error occurs.
Methods
- constructor
- Initializes the client
- Parameters
Object
: optional, options object
- Options
host
(String
): host name (localhost
)port
(Number
): port name (80
)path
(String
): path to intercept requests to (/engine.io
)resource
(String
): name of resource for this server (default
).
Setting a resource allows you to initialize multiple engine.io
endpoints on the same host without them interfering, and without
changing the path
directly.query
(Object
): optional query string addition (eg: { a: 'b' }
)secure
(`Boolean): whether the connection is secureupgrade
(Boolean
): defaults to true, whether the client should try
to upgrade the transport from long-polling to something better.forceJSONP
(Boolean
): forces JSONP for polling transport.timestampRequests
(Boolean
): whether to add the timestamp with
each transport request. Note: this is ignored if the browser is
IE or Android, in which case requests are always stamped (false
)timestampParam
(String
): timestamp parameter (t
)flashPath
(String
): path to flash client files with trailing slashpolicyPort
(Number
): port the policy server listens on (843
)transports
(Array
): a list of transports to try (in order).
Defaults to ['polling', 'websocket', 'flashsocket']
. Engine
always attempts to connect directly with the first one, provided the
feature detection test for it passes.
send
- Sends a message to the server
- Parameters
close
Transport
The transport class. Private. Inherits from EventEmitter.
Events
poll
: emitted by polling transports upon starting a new requestpollComplete
: emitted by polling transports upon completing a requestdrain
: emitted by polling transports upon a buffer drain
Flash transport
In order for the Flash transport to work correctly, ensure the flashPath
property points to the location where the files web_socket.js
,
swfobject.js
and WebSocketMainInsecure.swf
are located.
Tests
engine.io-client
is used to test
engine
Support
The support channels for engine.io-client
are the same as socket.io
:
Development
To contribute patches, run tests or benchmarks, make sure to clone the
repository:
git clone git://github.com/LearnBoost/engine.io-client.git
Then:
cd engine.io-client
npm install
License
(The MIT License)
Copyright (c) 2011 Guillermo Rauch <guillermo@learnboost.com>
Permission is hereby granted, free of charge, to any person obtaining
a copy of this software and associated documentation files (the
'Software'), to deal in the Software without restriction, including
without limitation the rights to use, copy, modify, merge, publish,
distribute, sublicense, and/or sell copies of the Software, and to
permit persons to whom the Software is furnished to do so, subject to
the following conditions:
The above copyright notice and this permission notice shall be
included in all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.