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app_vue/node_modules/faye-websocket/README.md
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# faye-websocket
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This is a general-purpose WebSocket implementation extracted from the
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[Faye](http://faye.jcoglan.com) project. It provides classes for easily building
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WebSocket servers and clients in Node. It does not provide a server itself, but
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rather makes it easy to handle WebSocket connections within an existing
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[Node](https://nodejs.org/) application. It does not provide any abstraction
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other than the standard [WebSocket
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API](https://html.spec.whatwg.org/multipage/comms.html#network).
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It also provides an abstraction for handling
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[EventSource](https://html.spec.whatwg.org/multipage/comms.html#server-sent-events)
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connections, which are one-way connections that allow the server to push data to
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the client. They are based on streaming HTTP responses and can be easier to access
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via proxies than WebSockets.
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## Installation
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```
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$ npm install faye-websocket
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```
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## Handling WebSocket connections in Node
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You can handle WebSockets on the server side by listening for HTTP Upgrade
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requests, and creating a new socket for the request. This socket object exposes
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the usual WebSocket methods for receiving and sending messages. For example this
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is how you'd implement an echo server:
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```js
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var WebSocket = require('faye-websocket'),
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http = require('http');
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var server = http.createServer();
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server.on('upgrade', function(request, socket, body) {
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if (WebSocket.isWebSocket(request)) {
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var ws = new WebSocket(request, socket, body);
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ws.on('message', function(event) {
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ws.send(event.data);
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});
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ws.on('close', function(event) {
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console.log('close', event.code, event.reason);
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ws = null;
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});
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}
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});
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server.listen(8000);
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```
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`WebSocket` objects are also duplex streams, so you could replace the
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`ws.on('message', ...)` line with:
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```js
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ws.pipe(ws);
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```
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Note that under certain circumstances (notably a draft-76 client connecting
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through an HTTP proxy), the WebSocket handshake will not be complete after you
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call `new WebSocket()` because the server will not have received the entire
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handshake from the client yet. In this case, calls to `ws.send()` will buffer
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the message in memory until the handshake is complete, at which point any
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buffered messages will be sent to the client.
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If you need to detect when the WebSocket handshake is complete, you can use the
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`onopen` event.
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If the connection's protocol version supports it, you can call `ws.ping()` to
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send a ping message and wait for the client's response. This method takes a
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message string, and an optional callback that fires when a matching pong message
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is received. It returns `true` if and only if a ping message was sent. If the
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client does not support ping/pong, this method sends no data and returns
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`false`.
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```js
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ws.ping('Mic check, one, two', function() {
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// fires when pong is received
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});
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```
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## Using the WebSocket client
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The client supports both the plain-text `ws` protocol and the encrypted `wss`
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protocol, and has exactly the same interface as a socket you would use in a web
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browser. On the wire it identifies itself as `hybi-13`.
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```js
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var WebSocket = require('faye-websocket'),
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ws = new WebSocket.Client('ws://www.example.com/');
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ws.on('open', function(event) {
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console.log('open');
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ws.send('Hello, world!');
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});
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ws.on('message', function(event) {
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console.log('message', event.data);
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});
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ws.on('close', function(event) {
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console.log('close', event.code, event.reason);
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ws = null;
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});
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```
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The WebSocket client also lets you inspect the status and headers of the
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handshake response via its `statusCode` and `headers` properties.
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To connect via a proxy, set the `proxy` option to the HTTP origin of the proxy,
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including any authorization information, custom headers and TLS config you
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require. Only the `origin` setting is required.
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```js
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var ws = new WebSocket.Client('ws://www.example.com/', [], {
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proxy: {
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origin: 'http://username:password@proxy.example.com',
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headers: { 'User-Agent': 'node' },
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tls: { cert: fs.readFileSync('client.crt') }
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}
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});
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```
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The `tls` value is an object that will be passed to
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[`tls.connect()`](https://nodejs.org/api/tls.html#tls_tls_connect_options_callback).
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## Subprotocol negotiation
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The WebSocket protocol allows peers to select and identify the application
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protocol to use over the connection. On the client side, you can set which
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protocols the client accepts by passing a list of protocol names when you
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construct the socket:
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```js
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var ws = new WebSocket.Client('ws://www.example.com/', ['irc', 'amqp']);
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```
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On the server side, you can likewise pass in the list of protocols the server
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supports after the other constructor arguments:
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```js
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var ws = new WebSocket(request, socket, body, ['irc', 'amqp']);
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```
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If the client and server agree on a protocol, both the client- and server-side
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socket objects expose the selected protocol through the `ws.protocol` property.
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## Protocol extensions
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faye-websocket is based on the
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[websocket-extensions](https://github.com/faye/websocket-extensions-node)
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framework that allows extensions to be negotiated via the
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`Sec-WebSocket-Extensions` header. To add extensions to a connection, pass an
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array of extensions to the `:extensions` option. For example, to add
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[permessage-deflate](https://github.com/faye/permessage-deflate-node):
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```js
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var deflate = require('permessage-deflate');
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var ws = new WebSocket(request, socket, body, [], { extensions: [deflate] });
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```
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## Initialization options
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Both the server- and client-side classes allow an options object to be passed in
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at initialization time, for example:
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```js
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var ws = new WebSocket(request, socket, body, protocols, options);
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var ws = new WebSocket.Client(url, protocols, options);
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```
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`protocols` is an array of subprotocols as described above, or `null`.
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`options` is an optional object containing any of these fields:
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- `extensions` - an array of
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[websocket-extensions](https://github.com/faye/websocket-extensions-node)
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compatible extensions, as described above
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- `headers` - an object containing key-value pairs representing HTTP headers to
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be sent during the handshake process
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- `maxLength` - the maximum allowed size of incoming message frames, in bytes.
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The default value is `2^26 - 1`, or 1 byte short of 64 MiB.
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- `ping` - an integer that sets how often the WebSocket should send ping frames,
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measured in seconds
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The client accepts some additional options:
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- `proxy` - settings for a proxy as described above
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- `net` - an object containing settings for the origin server that will be
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passed to
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[`net.connect()`](https://nodejs.org/api/net.html#net_socket_connect_options_connectlistener)
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- `tls` - an object containing TLS settings for the origin server, this will be
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passed to
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[`tls.connect()`](https://nodejs.org/api/tls.html#tls_tls_connect_options_callback)
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- `ca` - (legacy) a shorthand for passing `{ tls: { ca: value } }`
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## WebSocket API
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Both server- and client-side `WebSocket` objects support the following API.
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- **`on('open', function(event) {})`** fires when the socket connection is
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established. Event has no attributes.
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- **`on('message', function(event) {})`** fires when the socket receives a
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message. Event has one attribute, **`data`**, which is either a `String` (for
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text frames) or a `Buffer` (for binary frames).
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- **`on('error', function(event) {})`** fires when there is a protocol error due
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to bad data sent by the other peer. This event is purely informational, you do
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not need to implement error recover.
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- **`on('close', function(event) {})`** fires when either the client or the
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server closes the connection. Event has two optional attributes, **`code`**
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and **`reason`**, that expose the status code and message sent by the peer
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that closed the connection.
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- **`send(message)`** accepts either a `String` or a `Buffer` and sends a text
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or binary message over the connection to the other peer.
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- **`ping(message, function() {})`** sends a ping frame with an optional message
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and fires the callback when a matching pong is received.
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- **`close(code, reason)`** closes the connection, sending the given status code
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and reason text, both of which are optional.
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- **`version`** is a string containing the version of the `WebSocket` protocol
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the connection is using.
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- **`protocol`** is a string (which may be empty) identifying the subprotocol
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the socket is using.
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## Handling EventSource connections in Node
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EventSource connections provide a very similar interface, although because they
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only allow the server to send data to the client, there is no `onmessage` API.
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EventSource allows the server to push text messages to the client, where each
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message has an optional event-type and ID.
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```js
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var WebSocket = require('faye-websocket'),
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EventSource = WebSocket.EventSource,
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http = require('http');
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var server = http.createServer();
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server.on('request', function(request, response) {
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if (EventSource.isEventSource(request)) {
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var es = new EventSource(request, response);
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console.log('open', es.url, es.lastEventId);
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// Periodically send messages
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var loop = setInterval(function() { es.send('Hello') }, 1000);
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es.on('close', function() {
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clearInterval(loop);
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es = null;
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});
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} else {
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// Normal HTTP request
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response.writeHead(200, { 'Content-Type': 'text/plain' });
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response.end('Hello');
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}
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});
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server.listen(8000);
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```
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The `send` method takes two optional parameters, `event` and `id`. The default
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event-type is `'message'` with no ID. For example, to send a `notification`
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event with ID `99`:
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```js
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es.send('Breaking News!', { event: 'notification', id: '99' });
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```
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The `EventSource` object exposes the following properties:
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- **`url`** is a string containing the URL the client used to create the
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EventSource.
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- **`lastEventId`** is a string containing the last event ID received by the
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client. You can use this when the client reconnects after a dropped connection
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to determine which messages need resending.
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When you initialize an EventSource with ` new EventSource()`, you can pass
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configuration options after the `response` parameter. Available options are:
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- **`headers`** is an object containing custom headers to be set on the
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EventSource response.
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- **`retry`** is a number that tells the client how long (in seconds) it should
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wait after a dropped connection before attempting to reconnect.
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- **`ping`** is a number that tells the server how often (in seconds) to send
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'ping' packets to the client to keep the connection open, to defeat timeouts
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set by proxies. The client will ignore these messages.
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For example, this creates a connection that allows access from any origin, pings
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every 15 seconds and is retryable every 10 seconds if the connection is broken:
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```js
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var es = new EventSource(request, response, {
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headers: { 'Access-Control-Allow-Origin': '*' },
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ping: 15,
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retry: 10
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});
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```
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You can send a ping message at any time by calling `es.ping()`. Unlike
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WebSocket, the client does not send a response to this; it is merely to send
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some data over the wire to keep the connection alive.
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