js/tcp-client.js

   1 /*
   2 Copyright 2012 Google Inc.
   3
   4 Licensed under the Apache License, Version 2.0 (the "License");
   5 you may not use this file except in compliance with the License.
   6 You may obtain a copy of the License at
   7
   8      http://www.apache.org/licenses/LICENSE-2.0
   9
  10 Unless required by applicable law or agreed to in writing, software
  11 distributed under the License is distributed on an "AS IS" BASIS,
  12 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  13 See the License for the specific language governing permissions and
  14 limitations under the License.
  15
  16 Author: Boris Smus (smus@chromium.org)
  17 */
  18
  19 (function(exports) {
  20
  21   // Define some local variables here.
  22   var socket = chrome.socket;
  23
  24   /**
  25    * Creates an instance of the client
  26    *
  27    * @param {String} host The remote host to connect to
  28    * @param {Number} port The port to connect to at the remote host
  29    */
  30   function TcpClient(host, port) {
  31     this.host = host;
  32     this.port = port;
  33
  34     // Callback functions.
  35     this.callbacks = {
  36       connect: null,    // Called when socket is connected.
  37       disconnect: null, // Called when socket is disconnected.
  38       recv: null,       // Called when client receives data from server.
  39       sent: null        // Called when client sends data to server.
  40     };
  41
  42     // Socket.
  43     this.socketId = null;
  44     this.isConnected = false;
  45     this.pollerId = null;
  46
  47     log('initialized tcp client');
  48   }
  49
  50   /**
  51    * Connects to the TCP socket, and creates an open socket.
  52    *
  53    * @see http://developer.chrome.com/apps/socket.html#method-create
  54    * @param {Function} callback The function to call on connection
  55    */
  56   TcpClient.prototype.connect = function(callback) {
  57     socket.create('tcp', {}, this._onCreate.bind(this));
  58
  59     // Register connect callback.
  60     this.callbacks.connect = callback;
  61   };
  62
  63   /**
  64    * Sends a message down the wire to the remote side
  65    *
  66    * @see http://developer.chrome.com/apps/socket.html#method-write
  67    * @param {String} msg The message to send
  68    * @param {Function} callback The function to call when the message has sent
  69    */
  70   TcpClient.prototype.sendMessage = function(msg, callback) {
  71     this._stringToArrayBuffer(msg + '\n', function(arrayBuffer) {
  72       socket.write(this.socketId, arrayBuffer, this._onWriteComplete.bind(this));
  73     }.bind(this));
  74
  75     // Register sent callback.
  76     this.callbacks.sent = callback;
  77   };
  78
  79   /**
  80    * Sets the callback for when a message is received
  81    *
  82    * @param {Function} callback The function to call when a message has arrived
  83    */
  84   TcpClient.prototype.addResponseListener = function(callback) {
  85     // Register received callback.
  86     this.callbacks.recv = callback;
  87   };
  88
  89   /**
  90    * Disconnects from the remote side
  91    *
  92    * @see http://developer.chrome.com/apps/socket.html#method-disconnect
  93    */
  94   TcpClient.prototype.disconnect = function() {
  95     socket.disconnect(this.socketId);
  96     if (this.isConnected) {
  97       clearInterval(this.pollerId);
  98       this.pollerId = null;
  99       this.isConnected = false;
 100     }
 101   };
 102
 103   /**
 104    * The callback function used for when we attempt to have Chrome
 105    * create a socket. If the socket is successfully created
 106    * we go ahead and connect to the remote side.
 107    *
 108    * @private
 109    * @see http://developer.chrome.com/apps/socket.html#method-connect
 110    * @param {Object} createInfo The socket details
 111    */
 112   TcpClient.prototype._onCreate = function(createInfo) {
 113     this.socketId = createInfo.socketId;
 114     if (this.socketId > 0) {
 115       socket.connect(this.socketId, this.host, this.port, this._onConnectComplete.bind(this));
 116     } else {
 117       error('Unable to create socket');
 118     }
 119   };
 120
 121   /**
 122    * The callback function used for when we attempt to have Chrome
 123    * connect to the remote side. If a successful connection is
 124    * made then polling starts to check for data to read
 125    *
 126    * @private
 127    * @param {Number} resultCode Indicates whether the connection was successful
 128    */
 129   TcpClient.prototype._onConnectComplete = function(resultCode) {
 130     log('resultCode: ' + resultCode);
 131
 132     // XXX: Can this ever be positive ?
 133     this.isConnected = (resultCode >= 0);
 134
 135     // Start polling for reads.
 136     clearInterval(this.pollerId);
 137     if (this.isConnected) {
 138       this.pollerId = setInterval(this.poll.bind(this), 500);
 139     }
 140
 141     if (this.callbacks.connect) {
 142       log('connect complete');
 143       this.callbacks.connect(resultCode);
 144     }
 145     log('onConnectComplete');
 146   };
 147
 148   /**
 149    * Checks for new data to read from the socket
 150    *
 151    * @see http://developer.chrome.com/apps/socket.html#method-read
 152    */
 153   TcpClient.prototype.poll = function() {
 154     socket.read(this.socketId, null, this._onDataRead.bind(this));
 155   };
 156
 157   /**
 158    * Callback function for when data has been read from the socket.
 159    * Converts the array buffer that is read in to a string
 160    * and sends it on for further processing by passing it to
 161    * the previously assigned callback function.
 162    *
 163    * @private
 164    * @see TcpClient.prototype.addResponseListener
 165    * @param {Object} readInfo The incoming message
 166    */
 167   TcpClient.prototype._onDataRead = function(readInfo) {
 168     // Call received callback if there's data in the response.
 169     if (readInfo.resultCode > 0 && this.callbacks.recv) {
 170       log('onDataRead');
 171       // Convert ArrayBuffer to string.
 172       this._arrayBufferToString(readInfo.data, function(str) {
 173         this.callbacks.recv(str);
 174       }.bind(this));
 175     }
 176   };
 177
 178   /**
 179    * Callback for when data has been successfully
 180    * written to the socket.
 181    *
 182    * @private
 183    * @param {Object} writeInfo The outgoing message
 184    */
 185   TcpClient.prototype._onWriteComplete = function(writeInfo) {
 186     log('onWriteComplete');
 187     // Call sent callback.
 188     if (this.callbacks.sent) {
 189       this.callbacks.sent(writeInfo);
 190     }
 191   };
 192
 193   /**
 194    * Converts an array buffer to a string
 195    *
 196    * @private
 197    * @param {ArrayBuffer} buf The buffer to convert
 198    * @param {Function} callback The function to call when conversion is complete
 199    */
 200   TcpClient.prototype._arrayBufferToString = function(buf, callback) {
 201     var bb = new Blob([new Uint8Array(buf)]);
 202     var f = new FileReader();
 203     f.onload = function(e) {
 204       callback(e.target.result);
 205     };
 206     f.readAsText(bb);
 207   };
 208
 209   /**
 210    * Converts a string to an array buffer
 211    *
 212    * @private
 213    * @param {String} str The string to convert
 214    * @param {Function} callback The function to call when conversion is complete
 215    */
 216   TcpClient.prototype._stringToArrayBuffer = function(str, callback) {
 217     var bb = new Blob([str]);
 218     var f = new FileReader();
 219     f.onload = function(e) {
 220         callback(e.target.result);
 221     };
 222     f.readAsArrayBuffer(bb);
 223   };
 224
 225   /**
 226    * Wrapper function for logging
 227    */
 228   function log(msg) {
 229     //console.log('tcp-client:', msg);
 230   }
 231
 232   /**
 233    * Wrapper function for error logging
 234    */
 235   function error(msg) {
 236     console.error('tcp-client:', msg);
 237   }
 238
 239   exports.TcpClient = TcpClient;
 240
 241 })(window);