WebSocket protocol handler with pluggable I/O
This module provides a complete implementation of the WebSocket protocols that can be hooked up to any I/O stream. It aims to simplify things by decoupling the protocol details from the I/O layer, such that users only need to implement code to stream data in and out of it without needing to know anything about how the protocol actually works. Think of it as a complete WebSocket system with pluggable I/O.
Due to this design, you get a lot of things for free. In particular, if you hook this module up to some I/O object, it will do all of this for you:
This library was originally extracted from the Faye project but now aims to provide simple WebSocket support for any Node-based project.
$ npm install websocket-driver
This module provides protocol drivers that have the same interface on the server and on the client. A WebSocket driver is an object with two duplex streams attached; one for incoming/outgoing messages and one for managing the wire protocol over an I/O stream. The full API is described below.
A Node webserver emits a special event for 'upgrade' requests, and this is where you should handle WebSockets. You first check whether the request is a WebSocket, and if so you can create a driver and attach the request's I/O stream to it.
var http =websocket = ;var server = http;server;
Note the line
driver.io.write(body) - you must pass the
body buffer to the
socket driver in order to make certain versions of the protocol work.
You can also handle WebSocket connections in a bare TCP server, if you're not using an HTTP server and don't want to implement HTTP parsing yourself.
The driver will emit a
connect event when a request is received, and at this
point you can detect whether it's a WebSocket and handle it as such. Here's an
example using the Node
var net =websocket = ;var server = net;server;
connect event, the driver gains several properties to describe the
request, similar to a Node request object, such as
headers. However you should remember it's not a real request object; you
cannot write data to it, it only tells you what request data we parsed from the
If the request has a body, it will be in the
driver.body buffer, but only as
much of the body as has been piped into the driver when the
Similarly, to implement a WebSocket client you just need to make a driver by passing in a URL. After this you use the driver API as described below to process incoming data and send outgoing data.
var net =websocket = ;var driver = websockettcp = net;tcp;tcp;drivermessages;
Client drivers have two additional properties for reading the HTTP data that was sent back by the server:
driver.statusCode- the integer value of the HTTP status code
driver.headers- an object containing the response headers
The client driver supports connections via HTTP proxies using the
method. Instead of sending the WebSocket handshake immediately, it will send a
CONNECT request, wait for a
200 response, and then proceed as normal.
To use this feature, call
url is the origin of the
proxy, including a username and password if required. This produces a duplex
stream that you should pipe in and out of your TCP connection to the proxy
server. When the proxy emits
connect, you can then pipe
driver.io to your
TCP stream and call
var net =websocket = ;var driver = websocketproxy = drivertcp = net;tcp;tcp;proxy;drivermessages;
connect event is also where you should perform a TLS handshake on
your TCP stream, if you are connecting to a
In the event that proxy connection fails,
proxy will emit an
error. You can
inspect the proxy's response via
proxy.start() you can set custom headers using
Drivers are created using one of the following methods:
driver = websocketdriver = websocketdriver = websocket
http method returns a driver chosen using the headers from a Node HTTP
request object. The
server method returns a driver that will parse an HTTP
request and then decide which driver to use for it using the
http method. The
client method always returns a driver for the RFC version of the protocol with
masking enabled on outgoing frames.
options argument is optional, and is an object. It may contain the
maxLength- the maximum allowed size of incoming message frames, in bytes. The default value is
2^26 - 1, or 1 byte short of 64 MiB.
protocols- an array of strings representing acceptable subprotocols for use over the socket. The driver will negotiate one of these to use via the
Sec-WebSocket-Protocolheader if supported by the other peer.
A driver has two duplex streams attached to it:
driver.io- this stream should be attached to an I/O socket like a TCP stream. Pipe incoming TCP chunks to this stream for them to be parsed, and pipe this stream back into TCP to send outgoing frames.
driver.messages- this stream emits messages received over the WebSocket. Writing to it sends messages to the other peer by emitting frames via the
All drivers respond to the following API methods, but some of them are no-ops depending on whether the client supports the behaviour.
Note that most of these methods are commands: if they produce data that should
be sent over the socket, they will give this to you by emitting
data events on
Adds a callback to execute when the socket becomes open.
Adds a callback to execute when a message is received.
event will have a
data attribute containing either a string in the case of a text message or a
Buffer in the case of a binary message.
You can also listen for messages using the
which emits strings for text messages and buffers for binary messages.
Adds a callback to execute when a protocol error occurs due to the other peer
sending an invalid byte sequence.
event will have a
describing the error.
Adds a callback to execute when the socket becomes closed. The
Registers a protocol extension whose operation will be negotiated via the
extension is any extension compatible with
Sets a custom header to be sent as part of the handshake response, either from
the server or from the client. Must be called before
start(), since this is
when the headers are serialized and sent.
Initiates the protocol by sending the handshake - either the response for a
server-side driver or the request for a client-side one. This should be the
first method you invoke. Returns
true if and only if a handshake was sent.
Takes a string and parses it, potentially resulting in message events being
on('message') above) or in data being sent to
should send all data you receive via I/O to this method by piping a stream into
Sends a text message over the socket. If the socket handshake is not yet
complete, the message will be queued until it is. Returns
true if the message
was sent or queued, and
false if the socket can no longer send messages.
This method is equivalent to
Buffer and sends it as a binary message. Will queue and return
false the same way as the
text method. It will also return
false if the
driver does not support binary messages.
This method is equivalent to
Sends a ping frame over the socket, queueing it if necessary.
string and the
callback are both optional. If a callback is given, it will be invoked when the
socket receives a pong frame whose content matches
frames can no longer be sent, or if the driver does not support ping/pong.
Sends a pong frame over the socket, queueing it if necessary.
false if frames can no longer be sent, or if the driver does
not support ping/pong.
You don't need to call this when a ping frame is received; pings are replied to automatically by the driver. This method is for sending unsolicited pongs.
Initiates the closing handshake if the socket is still open. For drivers with no
closing handshake, this will result in the immediate execution of the
on('close') driver. For drivers with a closing handshake, this sends a closing
emit('close') will execute when a response is received or a protocol
Returns the WebSocket version in use as a string. Will either be
Returns a string containing the selected subprotocol, if any was agreed upon
Sec-WebSocket-Protocol mechanism. This value becomes available after
emit('open') has fired.
(The MIT License)
Copyright (c) 2010-2016 James Coglan
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