1 | # faye-websocket
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2 |
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3 | This is a general-purpose WebSocket implementation extracted from the
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4 | [Faye](http://faye.jcoglan.com) project. It provides classes for easily building
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5 | WebSocket servers and clients in Node. It does not provide a server itself, but
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6 | rather makes it easy to handle WebSocket connections within an existing
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7 | [Node](https://nodejs.org/) application. It does not provide any abstraction
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8 | other than the standard [WebSocket
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9 | API](https://html.spec.whatwg.org/multipage/comms.html#network).
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10 |
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11 | It also provides an abstraction for handling
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12 | [EventSource](https://html.spec.whatwg.org/multipage/comms.html#server-sent-events)
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13 | connections, which are one-way connections that allow the server to push data to
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14 | the client. They are based on streaming HTTP responses and can be easier to access
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15 | via proxies than WebSockets.
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16 |
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17 |
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18 | ## Installation
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19 |
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20 | ```
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21 | $ npm install faye-websocket
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22 | ```
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23 |
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24 |
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25 | ## Handling WebSocket connections in Node
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26 |
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27 | You can handle WebSockets on the server side by listening for HTTP Upgrade
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28 | requests, and creating a new socket for the request. This socket object exposes
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29 | the usual WebSocket methods for receiving and sending messages. For example this
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30 | is how you'd implement an echo server:
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31 |
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32 | ```js
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33 | var WebSocket = require('faye-websocket'),
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34 | http = require('http');
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35 |
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36 | var server = http.createServer();
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37 |
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38 | server.on('upgrade', function(request, socket, body) {
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39 | if (WebSocket.isWebSocket(request)) {
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40 | var ws = new WebSocket(request, socket, body);
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41 |
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42 | ws.on('message', function(event) {
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43 | ws.send(event.data);
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44 | });
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45 |
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46 | ws.on('close', function(event) {
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47 | console.log('close', event.code, event.reason);
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48 | ws = null;
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49 | });
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50 | }
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51 | });
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52 |
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53 | server.listen(8000);
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54 | ```
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55 |
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56 | `WebSocket` objects are also duplex streams, so you could replace the
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57 | `ws.on('message', ...)` line with:
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58 |
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59 | ```js
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60 | ws.pipe(ws);
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61 | ```
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62 |
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63 | Note that under certain circumstances (notably a draft-76 client connecting
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64 | through an HTTP proxy), the WebSocket handshake will not be complete after you
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65 | call `new WebSocket()` because the server will not have received the entire
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66 | handshake from the client yet. In this case, calls to `ws.send()` will buffer
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67 | the message in memory until the handshake is complete, at which point any
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68 | buffered messages will be sent to the client.
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69 |
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70 | If you need to detect when the WebSocket handshake is complete, you can use the
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71 | `onopen` event.
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72 |
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73 | If the connection's protocol version supports it, you can call `ws.ping()` to
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74 | send a ping message and wait for the client's response. This method takes a
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75 | message string, and an optional callback that fires when a matching pong message
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76 | is received. It returns `true` if and only if a ping message was sent. If the
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77 | client does not support ping/pong, this method sends no data and returns
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78 | `false`.
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79 |
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80 | ```js
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81 | ws.ping('Mic check, one, two', function() {
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82 | // fires when pong is received
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83 | });
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84 | ```
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85 |
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86 |
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87 | ## Using the WebSocket client
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88 |
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89 | The client supports both the plain-text `ws` protocol and the encrypted `wss`
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90 | protocol, and has exactly the same interface as a socket you would use in a web
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91 | browser. On the wire it identifies itself as `hybi-13`.
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92 |
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93 | ```js
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94 | var WebSocket = require('faye-websocket'),
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95 | ws = new WebSocket.Client('ws://www.example.com/');
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96 |
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97 | ws.on('open', function(event) {
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98 | console.log('open');
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99 | ws.send('Hello, world!');
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100 | });
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101 |
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102 | ws.on('message', function(event) {
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103 | console.log('message', event.data);
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104 | });
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105 |
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106 | ws.on('close', function(event) {
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107 | console.log('close', event.code, event.reason);
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108 | ws = null;
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109 | });
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110 | ```
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111 |
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112 | The WebSocket client also lets you inspect the status and headers of the
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113 | handshake response via its `statusCode` and `headers` properties.
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114 |
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115 | To connect via a proxy, set the `proxy` option to the HTTP origin of the proxy,
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116 | including any authorization information, custom headers and TLS config you
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117 | require. Only the `origin` setting is required.
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118 |
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119 | ```js
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120 | var ws = new WebSocket.Client('ws://www.example.com/', [], {
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121 | proxy: {
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122 | origin: 'http://username:password@proxy.example.com',
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123 | headers: { 'User-Agent': 'node' },
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124 | tls: { cert: fs.readFileSync('client.crt') }
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125 | }
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126 | });
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127 | ```
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128 |
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129 | The `tls` value is an object that will be passed to
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130 | [`tls.connect()`](https://nodejs.org/api/tls.html#tls_tls_connect_options_callback).
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131 |
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132 |
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133 | ## Subprotocol negotiation
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134 |
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135 | The WebSocket protocol allows peers to select and identify the application
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136 | protocol to use over the connection. On the client side, you can set which
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137 | protocols the client accepts by passing a list of protocol names when you
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138 | construct the socket:
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139 |
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140 | ```js
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141 | var ws = new WebSocket.Client('ws://www.example.com/', ['irc', 'amqp']);
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142 | ```
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143 |
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144 | On the server side, you can likewise pass in the list of protocols the server
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145 | supports after the other constructor arguments:
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146 |
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147 | ```js
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148 | var ws = new WebSocket(request, socket, body, ['irc', 'amqp']);
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149 | ```
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150 |
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151 | If the client and server agree on a protocol, both the client- and server-side
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152 | socket objects expose the selected protocol through the `ws.protocol` property.
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153 |
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154 |
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155 | ## Protocol extensions
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156 |
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157 | faye-websocket is based on the
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158 | [websocket-extensions](https://github.com/faye/websocket-extensions-node)
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159 | framework that allows extensions to be negotiated via the
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160 | `Sec-WebSocket-Extensions` header. To add extensions to a connection, pass an
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161 | array of extensions to the `:extensions` option. For example, to add
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162 | [permessage-deflate](https://github.com/faye/permessage-deflate-node):
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163 |
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164 | ```js
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165 | var deflate = require('permessage-deflate');
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166 |
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167 | var ws = new WebSocket(request, socket, body, [], { extensions: [deflate] });
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168 | ```
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169 |
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170 |
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171 | ## Initialization options
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172 |
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173 | Both the server- and client-side classes allow an options object to be passed in
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174 | at initialization time, for example:
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175 |
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176 | ```js
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177 | var ws = new WebSocket(request, socket, body, protocols, options);
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178 | var ws = new WebSocket.Client(url, protocols, options);
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179 | ```
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180 |
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181 | `protocols` is an array of subprotocols as described above, or `null`.
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182 | `options` is an optional object containing any of these fields:
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183 |
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184 | - `extensions` - an array of
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185 | [websocket-extensions](https://github.com/faye/websocket-extensions-node)
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186 | compatible extensions, as described above
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187 | - `headers` - an object containing key-value pairs representing HTTP headers to
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188 | be sent during the handshake process
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189 | - `maxLength` - the maximum allowed size of incoming message frames, in bytes.
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190 | The default value is `2^26 - 1`, or 1 byte short of 64 MiB.
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191 | - `ping` - an integer that sets how often the WebSocket should send ping frames,
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192 | measured in seconds
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193 |
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194 | The client accepts some additional options:
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195 |
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196 | - `proxy` - settings for a proxy as described above
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197 | - `net` - an object containing settings for the origin server that will be
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198 | passed to
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199 | [`net.connect()`](https://nodejs.org/api/net.html#net_socket_connect_options_connectlistener)
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200 | - `tls` - an object containing TLS settings for the origin server, this will be
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201 | passed to
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202 | [`tls.connect()`](https://nodejs.org/api/tls.html#tls_tls_connect_options_callback)
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203 | - `ca` - (legacy) a shorthand for passing `{ tls: { ca: value } }`
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204 |
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205 |
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206 | ## WebSocket API
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207 |
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208 | Both server- and client-side `WebSocket` objects support the following API.
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209 |
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210 | - **`on('open', function(event) {})`** fires when the socket connection is
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211 | established. Event has no attributes.
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212 | - **`on('message', function(event) {})`** fires when the socket receives a
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213 | message. Event has one attribute, **`data`**, which is either a `String` (for
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214 | text frames) or a `Buffer` (for binary frames).
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215 | - **`on('error', function(event) {})`** fires when there is a protocol error due
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216 | to bad data sent by the other peer. This event is purely informational, you do
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217 | not need to implement error recover.
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218 | - **`on('close', function(event) {})`** fires when either the client or the
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219 | server closes the connection. Event has two optional attributes, **`code`**
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220 | and **`reason`**, that expose the status code and message sent by the peer
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221 | that closed the connection.
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222 | - **`send(message)`** accepts either a `String` or a `Buffer` and sends a text
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223 | or binary message over the connection to the other peer.
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224 | - **`ping(message, function() {})`** sends a ping frame with an optional message
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225 | and fires the callback when a matching pong is received.
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226 | - **`close(code, reason)`** closes the connection, sending the given status code
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227 | and reason text, both of which are optional.
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228 | - **`version`** is a string containing the version of the `WebSocket` protocol
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229 | the connection is using.
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230 | - **`protocol`** is a string (which may be empty) identifying the subprotocol
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231 | the socket is using.
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232 |
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233 |
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234 | ## Handling EventSource connections in Node
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235 |
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236 | EventSource connections provide a very similar interface, although because they
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237 | only allow the server to send data to the client, there is no `onmessage` API.
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238 | EventSource allows the server to push text messages to the client, where each
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239 | message has an optional event-type and ID.
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240 |
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241 | ```js
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242 | var WebSocket = require('faye-websocket'),
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243 | EventSource = WebSocket.EventSource,
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244 | http = require('http');
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245 |
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246 | var server = http.createServer();
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247 |
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248 | server.on('request', function(request, response) {
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249 | if (EventSource.isEventSource(request)) {
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250 | var es = new EventSource(request, response);
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251 | console.log('open', es.url, es.lastEventId);
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252 |
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253 | // Periodically send messages
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254 | var loop = setInterval(function() { es.send('Hello') }, 1000);
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255 |
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256 | es.on('close', function() {
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257 | clearInterval(loop);
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258 | es = null;
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259 | });
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260 |
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261 | } else {
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262 | // Normal HTTP request
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263 | response.writeHead(200, { 'Content-Type': 'text/plain' });
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264 | response.end('Hello');
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265 | }
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266 | });
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267 |
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268 | server.listen(8000);
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269 | ```
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270 |
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271 | The `send` method takes two optional parameters, `event` and `id`. The default
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272 | event-type is `'message'` with no ID. For example, to send a `notification`
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273 | event with ID `99`:
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274 |
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275 | ```js
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276 | es.send('Breaking News!', { event: 'notification', id: '99' });
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277 | ```
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278 |
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279 | The `EventSource` object exposes the following properties:
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280 |
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281 | - **`url`** is a string containing the URL the client used to create the
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282 | EventSource.
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283 | - **`lastEventId`** is a string containing the last event ID received by the
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284 | client. You can use this when the client reconnects after a dropped connection
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285 | to determine which messages need resending.
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286 |
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287 | When you initialize an EventSource with ` new EventSource()`, you can pass
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288 | configuration options after the `response` parameter. Available options are:
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289 |
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290 | - **`headers`** is an object containing custom headers to be set on the
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291 | EventSource response.
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292 | - **`retry`** is a number that tells the client how long (in seconds) it should
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293 | wait after a dropped connection before attempting to reconnect.
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294 | - **`ping`** is a number that tells the server how often (in seconds) to send
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295 | 'ping' packets to the client to keep the connection open, to defeat timeouts
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296 | set by proxies. The client will ignore these messages.
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297 |
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298 | For example, this creates a connection that allows access from any origin, pings
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299 | every 15 seconds and is retryable every 10 seconds if the connection is broken:
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300 |
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301 | ```js
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302 | var es = new EventSource(request, response, {
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303 | headers: { 'Access-Control-Allow-Origin': '*' },
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304 | ping: 15,
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305 | retry: 10
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306 | });
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307 | ```
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308 |
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309 | You can send a ping message at any time by calling `es.ping()`. Unlike
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310 | WebSocket, the client does not send a response to this; it is merely to send
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311 | some data over the wire to keep the connection alive.
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