mqttws31.js

/*******************************************************************************
 * Copyright (c) 2013 IBM Corp.
 *
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * and Eclipse Distribution License v1.0 which accompany this distribution.
 *
 * The Eclipse Public License is available at
 *    http://www.eclipse.org/legal/epl-v10.html
 * and the Eclipse Distribution License is available at
 *   http://www.eclipse.org/org/documents/edl-v10.php.
 *
 * Contributors:
 *    Andrew Banks - initial API and implementation and initial documentation
 *******************************************************************************/


// Only expose a single object name in the global namespace.
// Everything must go through this module. Global Messaging module
// only has a single public function, client, which returns
// a Messaging client object given connection details.

/**
 * Send and receive messages using web browsers.
 * <p>
 * This programming interface lets a JavaScript client application use the MQTT V3.1 protocol to
 * connect to an MQTT-supporting messaging server.
 *
 * The function supported includes:
 * <ol>
 * <li>Connecting to and disconnecting from a server. The server is identified by its host name and port number.
 * <li>Specifying options that relate to the communications link with the server,
 * for example the frequency of keep-alive heartbeats, and whether SSL/TLS is required.
 * <li>Subscribing to and receiving messages from MQTT Topics.
 * <li>Publishing messages to MQTT Topics.
 * </ol>
 * <p>
 * The API consists of two main objects:
 * <dl>
 * <dt><b>{@link Messaging.Client}</b></dt>
 * <dd>This contains methods that provide the functionality of the API,
 * including provision of callbacks that notify the application when a message
 * arrives from or is delivered to the messaging server,
 * or when the status of its connection to the messaging server changes.</dd>
 * <dt><b>{@link Messaging.Message}</b></dt>
 * <dd>This encapsulates the payload of the message along with various attributes
 * associated with its delivery, in particular the destination to which it has
 * been (or is about to be) sent.</dd>
 * </dl>
 * <p>
 * The programming interface validates parameters passed to it, and will throw
 * an Error containing an error message intended for developer use, if it detects
 * an error with any parameter.
 * <p>
 * Example:
 *
 * <code><pre>
 client = new Messaging.Client(location.hostname, Number(location.port), "clientId");
 client.onConnectionLost = onConnectionLost;
 client.onMessageArrived = onMessageArrived;
 client.connect({onSuccess:onConnect});

 function onConnect() {
// Once a connection has been made, make a subscription and send a message.
console.log("onConnect");
client.subscribe("/World");
message = new Messaging.Message("Hello");
message.destinationName = "/World";
client.send(message);
};
function onConnectionLost(responseObject) {
if (responseObject.errorCode !== 0)
console.log("onConnectionLost:"+responseObject.errorMessage);
};
function onMessageArrived(message) {
console.log("onMessageArrived:"+message.payloadString);
client.disconnect();
};
 * </pre></code>
 * @namespace Messaging
 */

Messaging = (function (global) {

	// Private variables below, these are only visible inside the function closure
	// which is used to define the module.

	var version = "@VERSION@";
	var buildLevel = "@BUILDLEVEL@";

	/**
	 * Unique message type identifiers, with associated
	 * associated integer values.
	 * @private
	 */
	var MESSAGE_TYPE = {
		CONNECT: 1,
		  CONNACK: 2,
		  PUBLISH: 3,
		  PUBACK: 4,
		  PUBREC: 5,
		  PUBREL: 6,
		  PUBCOMP: 7,
		  SUBSCRIBE: 8,
		  SUBACK: 9,
		  UNSUBSCRIBE: 10,
		  UNSUBACK: 11,
		  PINGREQ: 12,
		  PINGRESP: 13,
		  DISCONNECT: 14
	};

	// Collection of utility methods used to simplify module code
	// and promote the DRY pattern.

	/**
	 * Validate an object's parameter names to ensure they
	 * match a list of expected variables name for this option
	 * type. Used to ensure option object passed into the API don't
	 * contain erroneous parameters.
	 * @param {Object} obj - User options object
	 * @param {Object} keys - valid keys and types that may exist in obj.
	 * @throws {Error} Invalid option parameter found.
	 * @private
	 */
	var validate = function(obj, keys) {
		for(key in obj) {
			if (obj.hasOwnProperty(key)) {
				if (keys.hasOwnProperty(key)) {
					if (typeof obj[key] !== keys[key])
						throw new Error(format(ERROR.INVALID_TYPE, [typeof obj[key], key]));
				} else {
					var errorStr = "Unknown property, " + key + ". Valid properties are:";
					for (key in keys)
						if (keys.hasOwnProperty(key))
							errorStr = errorStr+" "+key;
					throw new Error(errorStr);
				}
			}
		}
	};

	/**
	 * Return a new function which runs the user function bound
	 * to a fixed scope.
	 * @param {function} User function
	 * @param {object} Function scope
	 * @return {function} User function bound to another scope
	 * @private
	 */
	var scope = function (f, scope) {
		return function () {
			return f.apply(scope, arguments);
		};
	};

	/**
	 * Unique message type identifiers, with associated
	 * associated integer values.
	 * @private
	 */
	var ERROR = {
		OK: {code:0, text:"AMQJSC0000I OK."},
		CONNECT_TIMEOUT: {code:1, text:"AMQJSC0001E Connect timed out."},
		SUBSCRIBE_TIMEOUT: {code:2, text:"AMQJS0002E Subscribe timed out."},
		UNSUBSCRIBE_TIMEOUT: {code:3, text:"AMQJS0003E Unsubscribe timed out."},
		PING_TIMEOUT: {code:4, text:"AMQJS0004E Ping timed out."},
		INTERNAL_ERROR: {code:5, text:"AMQJS0005E Internal error."},
		CONNACK_RETURNCODE: {code:6, text:"AMQJS0006E Bad Connack return code:{0} {1}."},
		SOCKET_ERROR: {code:7, text:"AMQJS0007E Socket error:{0}."},
		SOCKET_CLOSE: {code:8, text:"AMQJS0008I Socket closed."},
		MALFORMED_UTF: {code:9, text:"AMQJS0009E Malformed UTF data:{0} {1} {2}."},
		UNSUPPORTED: {code:10, text:"AMQJS0010E {0} is not supported by this browser."},
		INVALID_STATE: {code:11, text:"AMQJS0011E Invalid state {0}."},
		INVALID_TYPE: {code:12, text:"AMQJS0012E Invalid type {0} for {1}."},
		INVALID_ARGUMENT: {code:13, text:"AMQJS0013E Invalid argument {0} for {1}."},
		UNSUPPORTED_OPERATION: {code:14, text:"AMQJS0014E Unsupported operation."},
		INVALID_STORED_DATA: {code:15, text:"AMQJS0015E Invalid data in local storage key={0} value={1}."},
		INVALID_MQTT_MESSAGE_TYPE: {code:16, text:"AMQJS0016E Invalid MQTT message type {0}."},
		MALFORMED_UNICODE: {code:17, text:"AMQJS0017E Malformed Unicode string:{0} {1}."},
	};

	/** CONNACK RC Meaning. */
	var CONNACK_RC = {
		0:"Connection Accepted",
		1:"Connection Refused: unacceptable protocol version",
		2:"Connection Refused: identifier rejected",
		3:"Connection Refused: server unavailable",
		4:"Connection Refused: bad user name or password",
		5:"Connection Refused: not authorized"
	};

	/**
	 * Format an error message text.
	 * @private
	 * @param {error} ERROR.KEY value above.
	 * @param {substitutions} [array] substituted into the text.
	 * @return the text with the substitutions made.
	 */
	var format = function(error, substitutions) {
		var text = error.text;
		if (substitutions) {
			for (var i=0; i<substitutions.length; i++) {
				field = "{"+i+"}";
				start = text.indexOf(field);
				if(start > 0) {
					var part1 = text.substring(0,start);
					var part2 = text.substring(start+field.length);
					text = part1+substitutions[i]+part2;
				}
			}
		}
		return text;
	};

	//MQTT protocol and version        6    M    Q    I    s    d    p    3
	var MqttProtoIdentifier = [0x00,0x06,0x4d,0x51,0x49,0x73,0x64,0x70,0x03];

	/**
	 * Construct an MQTT wire protocol message.
	 * @param type MQTT packet type.
	 * @param options optional wire message attributes.
	 *
	 * Optional properties
	 *
	 * messageIdentifier: message ID in the range [0..65535]
	 * payloadMessage:	Application Message - PUBLISH only
	 * connectStrings:	array of 0 or more Strings to be put into the CONNECT payload
	 * topics:			array of strings (SUBSCRIBE, UNSUBSCRIBE)
	 * requestQoS:		array of QoS values [0..2]
	 *
	 * "Flag" properties
	 * cleanSession:	true if present / false if absent (CONNECT)
	 * willMessage:		true if present / false if absent (CONNECT)
	 * isRetained:		true if present / false if absent (CONNECT)
	 * userName:		true if present / false if absent (CONNECT)
	 * password:		true if present / false if absent (CONNECT)
	 * keepAliveInterval:	integer [0..65535]  (CONNECT)
	 *
	 * @private
	 * @ignore
	 */
	var WireMessage = function (type, options) {
		this.type = type;
		for(name in options) {
			if (options.hasOwnProperty(name)) {
				this[name] = options[name];
			}
		}
	};

	WireMessage.prototype.encode = function() {
		// Compute the first byte of the fixed header
		var first = ((this.type & 0x0f) << 4);

		/*
		 * Now calculate the length of the variable header + payload by adding up the lengths
		 * of all the component parts
		 */

		remLength = 0;
		topicStrLength = new Array();

		// if the message contains a messageIdentifier then we need two bytes for that
		if (this.messageIdentifier != undefined)
			remLength += 2;

		switch(this.type) {
			// If this a Connect then we need to include 12 bytes for its header
			case MESSAGE_TYPE.CONNECT:
				remLength += MqttProtoIdentifier.length + 3;
				remLength += UTF8Length(this.clientId) + 2;
				if (this.willMessage != undefined) {
					remLength += UTF8Length(this.willMessage.destinationName) + 2;
					// Will message is always a string, sent as UTF-8 characters with a preceding length.
					var willMessagePayloadBytes = this.willMessage.payloadBytes;
					if (!(willMessagePayloadBytes instanceof Uint8Array))
						willMessagePayloadBytes = new Uint8Array(payloadBytes);
					remLength += willMessagePayloadBytes.byteLength +2;
				}
				if (this.userName != undefined)
					remLength += UTF8Length(this.userName) + 2;
				if (this.password != undefined)
					remLength += UTF8Length(this.password) + 2;
				break;

				// Subscribe, Unsubscribe can both contain topic strings
			case MESSAGE_TYPE.SUBSCRIBE:
				first |= 0x02; // Qos = 1;
				for ( var i = 0; i < this.topics.length; i++) {
					topicStrLength[i] = UTF8Length(this.topics[i]);
					remLength += topicStrLength[i] + 2;
				}
				remLength += this.requestedQos.length; // 1 byte for each topic's Qos
				// QoS on Subscribe only
				break;

			case MESSAGE_TYPE.UNSUBSCRIBE:
				first |= 0x02; // Qos = 1;
				for ( var i = 0; i < this.topics.length; i++) {
					topicStrLength[i] = UTF8Length(this.topics[i]);
					remLength += topicStrLength[i] + 2;
				}
				break;

			case MESSAGE_TYPE.PUBLISH:
				if (this.payloadMessage.duplicate) first |= 0x08;
				first  = first |= (this.payloadMessage.qos << 1);
				if (this.payloadMessage.retained) first |= 0x01;
				destinationNameLength = UTF8Length(this.payloadMessage.destinationName);
				remLength += destinationNameLength + 2;
				var payloadBytes = this.payloadMessage.payloadBytes;
				remLength += payloadBytes.byteLength;
				if (payloadBytes instanceof ArrayBuffer)
					payloadBytes = new Uint8Array(payloadBytes);
				else if (!(payloadBytes instanceof Uint8Array))
					payloadBytes = new Uint8Array(payloadBytes.buffer);
				break;

			case MESSAGE_TYPE.DISCONNECT:
				break;

			default:
				;
		}

		// Now we can allocate a buffer for the message

		var mbi = encodeMBI(remLength);  // Convert the length to MQTT MBI format
		var pos = mbi.length + 1;        // Offset of start of variable header
		var buffer = new ArrayBuffer(remLength + pos);
		var byteStream = new Uint8Array(buffer);    // view it as a sequence of bytes

		//Write the fixed header into the buffer
		byteStream[0] = first;
		byteStream.set(mbi,1);

		// If this is a PUBLISH then the variable header starts with a topic
		if (this.type == MESSAGE_TYPE.PUBLISH)
			pos = writeString(this.payloadMessage.destinationName, destinationNameLength, byteStream, pos);
		// If this is a CONNECT then the variable header contains the protocol name/version, flags and keepalive time

		else if (this.type == MESSAGE_TYPE.CONNECT) {
			byteStream.set(MqttProtoIdentifier, pos);
			pos += MqttProtoIdentifier.length;
			var connectFlags = 0;
			if (this.cleanSession)
				connectFlags = 0x02;
			if (this.willMessage != undefined ) {
				connectFlags |= 0x04;
				connectFlags |= (this.willMessage.qos<<3);
				if (this.willMessage.retained) {
					connectFlags |= 0x20;
				}
			}
			if (this.userName != undefined)
				connectFlags |= 0x80;
			if (this.password != undefined)
				connectFlags |= 0x40;
			byteStream[pos++] = connectFlags;
			pos = writeUint16 (this.keepAliveInterval, byteStream, pos);
		}

		// Output the messageIdentifier - if there is one
		if (this.messageIdentifier != undefined)
			pos = writeUint16 (this.messageIdentifier, byteStream, pos);

		switch(this.type) {
			case MESSAGE_TYPE.CONNECT:
				pos = writeString(this.clientId, UTF8Length(this.clientId), byteStream, pos);
				if (this.willMessage != undefined) {
					pos = writeString(this.willMessage.destinationName, UTF8Length(this.willMessage.destinationName), byteStream, pos);
					pos = writeUint16(willMessagePayloadBytes.byteLength, byteStream, pos);
					byteStream.set(willMessagePayloadBytes, pos);
					pos += willMessagePayloadBytes.byteLength;

				}
				if (this.userName != undefined)
					pos = writeString(this.userName, UTF8Length(this.userName), byteStream, pos);
				if (this.password != undefined)
					pos = writeString(this.password, UTF8Length(this.password), byteStream, pos);
				break;

			case MESSAGE_TYPE.PUBLISH:
				// PUBLISH has a text or binary payload, if text do not add a 2 byte length field, just the UTF characters.
				byteStream.set(payloadBytes, pos);

				break;

				//			case MESSAGE_TYPE.PUBREC:
				//			case MESSAGE_TYPE.PUBREL:
				//			case MESSAGE_TYPE.PUBCOMP:
				//				break;

			case MESSAGE_TYPE.SUBSCRIBE:
				// SUBSCRIBE has a list of topic strings and request QoS
				for (var i=0; i<this.topics.length; i++) {
					pos = writeString(this.topics[i], topicStrLength[i], byteStream, pos);
					byteStream[pos++] = this.requestedQos[i];
				}
				break;

			case MESSAGE_TYPE.UNSUBSCRIBE:
				// UNSUBSCRIBE has a list of topic strings
				for (var i=0; i<this.topics.length; i++)
					pos = writeString(this.topics[i], topicStrLength[i], byteStream, pos);
				break;

			default:
				// Do nothing.
		}

		return buffer;
	}

	function decodeMessage(input,pos) {
		var startingPos = pos;
		var first = input[pos];
		var type = first >> 4;
		var messageInfo = first &= 0x0f;
		pos += 1;


		// Decode the remaining length (MBI format)

		var digit;
		var remLength = 0;
		var multiplier = 1;
		do {
			if (pos == input.length) {
				return [null,startingPos];
			}
			digit = input[pos++];
			remLength += ((digit & 0x7F) * multiplier);
			multiplier *= 128;
		} while ((digit & 0x80) != 0);

		var endPos = pos+remLength;
		if (endPos > input.length) {
			return [null,startingPos];
		}

		var wireMessage = new WireMessage(type);
		switch(type) {
			case MESSAGE_TYPE.CONNACK:
				wireMessage.topicNameCompressionResponse = input[pos++];
				wireMessage.returnCode = input[pos++];
				break;

			case MESSAGE_TYPE.PUBLISH:
				var qos = (messageInfo >> 1) & 0x03;

				var len = readUint16(input, pos);
				pos += 2;
				var topicName = parseUTF8(input, pos, len);
				pos += len;
				// If QoS 1 or 2 there will be a messageIdentifier
				if (qos > 0) {
					wireMessage.messageIdentifier = readUint16(input, pos);
					pos += 2;
				}

				var message = new Messaging.Message(input.subarray(pos, endPos));
				if ((messageInfo & 0x01) == 0x01)
					message.retained = true;
				if ((messageInfo & 0x08) == 0x08)
					message.duplicate =  true;
				message.qos = qos;
				message.destinationName = topicName;
				wireMessage.payloadMessage = message;
				break;

			case  MESSAGE_TYPE.PUBACK:
			case  MESSAGE_TYPE.PUBREC:
			case  MESSAGE_TYPE.PUBREL:
			case  MESSAGE_TYPE.PUBCOMP:
			case  MESSAGE_TYPE.UNSUBACK:
				wireMessage.messageIdentifier = readUint16(input, pos);
				break;

			case  MESSAGE_TYPE.SUBACK:
				wireMessage.messageIdentifier = readUint16(input, pos);
				pos += 2;
				wireMessage.grantedQos = input.subarray(pos);
				break;

			default:
				;
		}

		return [wireMessage,endPos];
	}

	function writeUint16(input, buffer, offset) {
		buffer[offset++] = input >> 8;      //MSB
		buffer[offset++] = input % 256;     //LSB
		return offset;
	}

	function writeString(input, utf8Length, buffer, offset) {
		offset = writeUint16(utf8Length, buffer, offset);
		stringToUTF8(input, buffer, offset);
		return offset + utf8Length;
	}

	function readUint16(buffer, offset) {
		return 256*buffer[offset] + buffer[offset+1];
	}

	/**
	 * Encodes an MQTT Multi-Byte Integer
	 * @private
	 */
	function encodeMBI(number) {
		var output = new Array(1);
		var numBytes = 0;

		do {
			var digit = number % 128;
			number = number >> 7;
			if (number > 0) {
				digit |= 0x80;
			}
			output[numBytes++] = digit;
		} while ( (number > 0) && (numBytes<4) );

		return output;
	}

	/**
	 * Takes a String and calculates its length in bytes when encoded in UTF8.
	 * @private
	 */
	function UTF8Length(input) {
		var output = 0;
		for (var i = 0; i<input.length; i++)
		{
			var charCode = input.charCodeAt(i);
			if (charCode > 0x7FF)
			{
				// Surrogate pair means its a 4 byte character
				if (0xD800 <= charCode && charCode <= 0xDBFF)
				{
					i++;
					output++;
				}
				output +=3;
			}
			else if (charCode > 0x7F)
				output +=2;
			else
				output++;
		}
		return output;
	}

	/**
	 * Takes a String and writes it into an array as UTF8 encoded bytes.
	 * @private
	 */
	function stringToUTF8(input, output, start) {
		var pos = start;
		for (var i = 0; i<input.length; i++) {
			var charCode = input.charCodeAt(i);

			// Check for a surrogate pair.
			if (0xD800 <= charCode && charCode <= 0xDBFF) {
				lowCharCode = input.charCodeAt(++i);
				if (isNaN(lowCharCode)) {
					throw new Error(format(ERROR.MALFORMED_UNICODE, [charCode, lowCharCode]));
				}
				charCode = ((charCode - 0xD800)<<10) + (lowCharCode - 0xDC00) + 0x10000;

			}

			if (charCode <= 0x7F) {
				output[pos++] = charCode;
			} else if (charCode <= 0x7FF) {
				output[pos++] = charCode>>6  & 0x1F | 0xC0;
				output[pos++] = charCode     & 0x3F | 0x80;
			} else if (charCode <= 0xFFFF) {
				output[pos++] = charCode>>12 & 0x0F | 0xE0;
				output[pos++] = charCode>>6  & 0x3F | 0x80;
				output[pos++] = charCode     & 0x3F | 0x80;
			} else {
				output[pos++] = charCode>>18 & 0x07 | 0xF0;
				output[pos++] = charCode>>12 & 0x3F | 0x80;
				output[pos++] = charCode>>6  & 0x3F | 0x80;
				output[pos++] = charCode     & 0x3F | 0x80;
			};
		}
		return output;
	}

	function parseUTF8(input, offset, length) {
		var output = "";
		var utf16;
		var pos = offset;

		while (pos < offset+length)
		{
			var byte1 = input[pos++];
			if (byte1 < 128)
				utf16 = byte1;
			else
			{
				var byte2 = input[pos++]-128;
				if (byte2 < 0)
					throw new Error(format(ERROR.MALFORMED_UTF, [byte1.toString(16), byte2.toString(16),""]));
				if (byte1 < 0xE0)             // 2 byte character
					utf16 = 64*(byte1-0xC0) + byte2;
				else
				{
					var byte3 = input[pos++]-128;
					if (byte3 < 0)
						throw new Error(format(ERROR.MALFORMED_UTF, [byte1.toString(16), byte2.toString(16), byte3.toString(16)]));
					if (byte1 < 0xF0)        // 3 byte character
						utf16 = 4096*(byte1-0xE0) + 64*byte2 + byte3;
					else
					{
						var byte4 = input[pos++]-128;
						if (byte4 < 0)
							throw new Error(format(ERROR.MALFORMED_UTF, [byte1.toString(16), byte2.toString(16), byte3.toString(16), byte4.toString(16)]));
						if (byte1 < 0xF8)        // 4 byte character
							utf16 = 262144*(byte1-0xF0) + 4096*byte2 + 64*byte3 + byte4;
						else                     // longer encodings are not supported
							throw new Error(format(ERROR.MALFORMED_UTF, [byte1.toString(16), byte2.toString(16), byte3.toString(16), byte4.toString(16)]));
					}
				}
			}

			if (utf16 > 0xFFFF)   // 4 byte character - express as a surrogate pair
			{
				utf16 -= 0x10000;
				output += String.fromCharCode(0xD800 + (utf16 >> 10)); // lead character
				utf16 = 0xDC00 + (utf16 & 0x3FF);  // trail character
			}
			output += String.fromCharCode(utf16);
		}
		return output;
	}

	/**
	 * Repeat keepalive requests, monitor responses.
	 * @ignore
	 */
	var Pinger = function(client, window, keepAliveInterval) {
		this._client = client;
		this._window = window;
		this._keepAliveInterval = keepAliveInterval*1000;
		this.isReset = false;

		var pingReq = new WireMessage(MESSAGE_TYPE.PINGREQ).encode();

		var doTimeout = function (pinger) {
			return function () {
				return doPing.apply(pinger);
			};
		};

		/** @ignore */
		var doPing = function() {
			if (!this.isReset) {
				this._client._trace("Pinger.doPing", "Timed out");
				this._client._disconnected( ERROR.PING_TIMEOUT.code , format(ERROR.PING_TIMEOUT));
			} else {
				this.isReset = false;
				this._client._trace("Pinger.doPing", "send PINGREQ");
				this._client.socket.send(pingReq);
				this.timeout = this._window.setTimeout(doTimeout(this), this._keepAliveInterval);
			}
		}

		this.reset = function() {
			this.isReset = true;
			this._window.clearTimeout(this.timeout);
			if (this._keepAliveInterval > 0)
				this.timeout = setTimeout(doTimeout(this), this._keepAliveInterval);
		}

		this.cancel = function() {
			this._window.clearTimeout(this.timeout);
		}
	};

	/**
	 * Monitor request completion.
	 * @ignore
	 */
	var Timeout = function(client, window, timeoutSeconds, action, args) {
		this._window = window;
		if (!timeoutSeconds)
			timeoutSeconds = 30;

		var doTimeout = function (action, client, args) {
			return function () {
				return action.apply(client, args);
			};
		};
		this.timeout = setTimeout(doTimeout(action, client, args), timeoutSeconds * 1000);

		this.cancel = function() {
			this._window.clearTimeout(this.timeout);
		}
	};

	/*
	 * Internal implementation of the Websockets MQTT V3.1 client.
	 *
	 * @name Messaging.ClientImpl @constructor
	 * @param {String} host the DNS nameof the webSocket host.
	 * @param {Number} port the port number for that host.
	 * @param {String} clientId the MQ client identifier.
	 */
	var ClientImpl = function (uri, host, port, path, clientId) {
		// Check dependencies are satisfied in this browser.
		if (!("WebSocket" in global && global["WebSocket"] !== null)) {
			throw new Error(format(ERROR.UNSUPPORTED, ["WebSocket"]));
		}
		if (!("localStorage" in global && global["localStorage"] !== null)) {
			throw new Error(format(ERROR.UNSUPPORTED, ["localStorage"]));
		}
		if (!("ArrayBuffer" in global && global["ArrayBuffer"] !== null)) {
			throw new Error(format(ERROR.UNSUPPORTED, ["ArrayBuffer"]));
		}
		this._trace("Messaging.Client", uri, host, port, path, clientId);

		this.host = host;
		this.port = port;
		this.path = path;
		this.uri = uri;
		this.clientId = clientId;

		// Local storagekeys are qualified with the following string.
		// The conditional inclusion of path in the key is for backward
		// compatibility to when the path was not configurable and assumed to
		// be /mqtt
		this._localKey=host+":"+port+(path!="/mqtt"?":"+path:"")+":"+clientId+":";

		// Create private instance-only message queue
		// Internal queue of messages to be sent, in sending order.
		this._msg_queue = [];

		// Messages we have sent and are expecting a response for, indexed by their respective message ids.
		this._sentMessages = {};

		// Messages we have received and acknowleged and are expecting a confirm message for
		// indexed by their respective message ids.
		this._receivedMessages = {};

		// Internal list of callbacks to be executed when messages
		// have been successfully sent over web socket, e.g. disconnect
		// when it doesn't have to wait for ACK, just message is dispatched.
		this._notify_msg_sent = {};

		// Unique identifier for SEND messages, incrementing
		// counter as messages are sent.
		this._message_identifier = 1;

		// Used to determine the transmission sequence of stored sent messages.
		this._sequence = 0;


		// Load the local state, if any, from the saved version, only restore state relevant to this client.
		for(key in localStorage)
			if (   key.indexOf("Sent:"+this._localKey) == 0
					|| key.indexOf("Received:"+this._localKey) == 0)
				this.restore(key);
	};

	// Messaging Client public instance members.
	ClientImpl.prototype.host;
	ClientImpl.prototype.port;
	ClientImpl.prototype.path;
	ClientImpl.prototype.uri;
	ClientImpl.prototype.clientId;

	// Messaging Client private instance members.
	ClientImpl.prototype.socket;
	/* true once we have received an acknowledgement to a CONNECT packet. */
	ClientImpl.prototype.connected = false;
	/* The largest message identifier allowed, may not be larger than 2**16 but
	 * if set smaller reduces the maximum number of outbound messages allowed.
	 */
	ClientImpl.prototype.maxMessageIdentifier = 65536;
	ClientImpl.prototype.connectOptions;
	ClientImpl.prototype.hostIndex;
	ClientImpl.prototype.onConnectionLost;
	ClientImpl.prototype.onMessageDelivered;
	ClientImpl.prototype.onMessageArrived;
	ClientImpl.prototype._msg_queue = null;
	ClientImpl.prototype._connectTimeout;
	/* The sendPinger monitors how long we allow before we send data to prove to the server that we are alive. */
	ClientImpl.prototype.sendPinger = null;
	/* The receivePinger monitors how long we allow before we require evidence that the server is alive. */
	ClientImpl.prototype.receivePinger = null;

	ClientImpl.prototype.receiveBuffer = null;

	ClientImpl.prototype._traceBuffer = null;
	ClientImpl.prototype._MAX_TRACE_ENTRIES = 100;

	ClientImpl.prototype.connect = function (connectOptions) {
		var connectOptionsMasked = this._traceMask(connectOptions, "password");
		this._trace("Client.connect", connectOptionsMasked, this.socket, this.connected);

		if (this.connected)
			throw new Error(format(ERROR.INVALID_STATE, ["already connected"]));
		if (this.socket)
			throw new Error(format(ERROR.INVALID_STATE, ["already connected"]));

		this.connectOptions = connectOptions;

		if (connectOptions.uris) {
			this.hostIndex = 0;
			this._doConnect(connectOptions.uris[0]);
		} else {
			this._doConnect(this.uri);
		}

	};

	ClientImpl.prototype.subscribe = function (filter, subscribeOptions) {
		this._trace("Client.subscribe", filter, subscribeOptions);

		if (!this.connected)
			throw new Error(format(ERROR.INVALID_STATE, ["not connected"]));

		var wireMessage = new WireMessage(MESSAGE_TYPE.SUBSCRIBE);
		wireMessage.topics=[filter];
		if (subscribeOptions.qos != undefined)
			wireMessage.requestedQos = [subscribeOptions.qos];
		else
			wireMessage.requestedQos = [0];

		if (subscribeOptions.onSuccess) {
			wireMessage.callback = function() {subscribeOptions.onSuccess({invocationContext:subscribeOptions.invocationContext});};
		}
		if (subscribeOptions.timeout) {
			wireMessage.timeOut = new Timeout(this, window, subscribeOptions.timeout, subscribeOptions.onFailure
					, [{invocationContext:subscribeOptions.invocationContext,
						errorCode:ERROR.SUBSCRIBE_TIMEOUT.code,
				errorMessage:format(ERROR.SUBSCRIBE_TIMEOUT)}]);
		}

		// All subscriptions return a SUBACK.
		this._requires_ack(wireMessage);
		this._schedule_message(wireMessage);
	};

	/** @ignore */
	ClientImpl.prototype.unsubscribe = function(filter, unsubscribeOptions) {
		this._trace("Client.unsubscribe", filter, unsubscribeOptions);

		if (!this.connected)
			throw new Error(format(ERROR.INVALID_STATE, ["not connected"]));

		var wireMessage = new WireMessage(MESSAGE_TYPE.UNSUBSCRIBE);
		wireMessage.topics = [filter];

		if (unsubscribeOptions.onSuccess) {
			wireMessage.callback = function() {unsubscribeOptions.onSuccess({invocationContext:unsubscribeOptions.invocationContext});};
		}
		if (unsubscribeOptions.timeout) {
			wireMessage.timeOut = new Timeout(this, window, unsubscribeOptions.timeout, unsubscribeOptions.onFailure
					, [{invocationContext:unsubscribeOptions.invocationContext,
						errorCode:ERROR.UNSUBSCRIBE_TIMEOUT.code,
				errorMessage:format(ERROR.UNSUBSCRIBE_TIMEOUT)}]);
		}

		// All unsubscribes return a SUBACK.
		this._requires_ack(wireMessage);
		this._schedule_message(wireMessage);
	};

	ClientImpl.prototype.send = function (message) {
		this._trace("Client.send", message);

		if (!this.connected)
			throw new Error(format(ERROR.INVALID_STATE, ["not connected"]));

		wireMessage = new WireMessage(MESSAGE_TYPE.PUBLISH);
		wireMessage.payloadMessage = message;

		if (message.qos > 0)
			this._requires_ack(wireMessage);
		else if (this.onMessageDelivered)
			this._notify_msg_sent[wireMessage] = this.onMessageDelivered(wireMessage.payloadMessage);
		this._schedule_message(wireMessage);
	};

	ClientImpl.prototype.disconnect = function () {
		this._trace("Client.disconnect");

		if (!this.socket)
			throw new Error(format(ERROR.INVALID_STATE, ["not connecting or connected"]));

		wireMessage = new WireMessage(MESSAGE_TYPE.DISCONNECT);

		// Run the disconnected call back as soon as the message has been sent,
		// in case of a failure later on in the disconnect processing.
		// as a consequence, the _disconected call back may be run several times.
		this._notify_msg_sent[wireMessage] = scope(this._disconnected, this);

		this._schedule_message(wireMessage);
	};

	ClientImpl.prototype.getTraceLog = function () {
		if ( this._traceBuffer !== null ) {
			this._trace("Client.getTraceLog", new Date());
			this._trace("Client.getTraceLog in flight messages", this._sentMessages.length);
			for (key in this._sentMessages)
				this._trace("_sentMessages ",key, this._sentMessages[key]);
			for (key in this._receivedMessages)
				this._trace("_receivedMessages ",key, this._receivedMessages[key]);

			return this._traceBuffer;
		}
	};

	ClientImpl.prototype.startTrace = function () {
		if ( this._traceBuffer === null ) {
			this._traceBuffer = [];
		}
		this._trace("Client.startTrace", new Date(), version);
	};

	ClientImpl.prototype.stopTrace = function () {
		delete this._traceBuffer;
	};

	ClientImpl.prototype._doConnect = function (wsurl) {
		// When the socket is open, this client will send the CONNECT WireMessage using the saved parameters.
		if (this.connectOptions.useSSL) {
			var uriParts = wsurl.split(":");
			uriParts[0] = "wss";
			wsurl = uriParts.join(":");
		}
		this.connected = false;
		this.socket = new WebSocket(wsurl, "mqttv3.1");
		this.socket.binaryType = 'arraybuffer';

		this.socket.onopen = scope(this._on_socket_open, this);
		this.socket.onmessage = scope(this._on_socket_message, this);
		this.socket.onerror = scope(this._on_socket_error, this);
		this.socket.onclose = scope(this._on_socket_close, this);

		this.sendPinger = new Pinger(this, window, this.connectOptions.keepAliveInterval);
		this.receivePinger = new Pinger(this, window, this.connectOptions.keepAliveInterval);

		this._connectTimeout = new Timeout(this, window, this.connectOptions.timeout, this._disconnected,  [ERROR.CONNECT_TIMEOUT.code, format(ERROR.CONNECT_TIMEOUT)]);
	};


	// Schedule a new message to be sent over the WebSockets
	// connection. CONNECT messages cause WebSocket connection
	// to be started. All other messages are queued internally
	// until this has happened. When WS connection starts, process
	// all outstanding messages.
	ClientImpl.prototype._schedule_message = function (message) {
		this._msg_queue.push(message);
		// Process outstanding messages in the queue if we have an  open socket, and have received CONNACK.
		if (this.connected) {
			this._process_queue();
		}
	};

	ClientImpl.prototype.store = function(prefix, wireMessage) {
		storedMessage = {type:wireMessage.type, messageIdentifier:wireMessage.messageIdentifier, version:1};

		switch(wireMessage.type) {
			case MESSAGE_TYPE.PUBLISH:
				if(wireMessage.pubRecReceived)
					storedMessage.pubRecReceived = true;

				// Convert the payload to a hex string.
				storedMessage.payloadMessage = {};
				var hex = "";
				var messageBytes = wireMessage.payloadMessage.payloadBytes;
				for (var i=0; i<messageBytes.length; i++) {
					if (messageBytes[i] <= 0xF)
						hex = hex+"0"+messageBytes[i].toString(16);
					else
						hex = hex+messageBytes[i].toString(16);
				}
				storedMessage.payloadMessage.payloadHex = hex;

				storedMessage.payloadMessage.qos = wireMessage.payloadMessage.qos;
				storedMessage.payloadMessage.destinationName = wireMessage.payloadMessage.destinationName;
				if (wireMessage.payloadMessage.duplicate)
					storedMessage.payloadMessage.duplicate = true;
				if (wireMessage.payloadMessage.retained)
					storedMessage.payloadMessage.retained = true;

				// Add a sequence number to sent messages.
				if ( prefix.indexOf("Sent:") == 0 ) {
					if ( wireMessage.sequence === undefined )
						wireMessage.sequence = ++this._sequence;
					storedMessage.sequence = wireMessage.sequence;
				}
				break;

			default:
				throw Error(format(ERROR.INVALID_STORED_DATA, [key, storedMessage]));
		}
		localStorage.setItem(prefix+this._localKey+wireMessage.messageIdentifier, JSON.stringify(storedMessage));
	};

	ClientImpl.prototype.restore = function(key) {
		var value = localStorage.getItem(key);
		var storedMessage = JSON.parse(value);

		var wireMessage = new WireMessage(storedMessage.type, storedMessage);

		switch(storedMessage.type) {
			case MESSAGE_TYPE.PUBLISH:
				// Replace the payload message with a Message object.
				var hex = storedMessage.payloadMessage.payloadHex;
				var buffer = new ArrayBuffer((hex.length)/2);
				var byteStream = new Uint8Array(buffer);
				var i = 0;
				while (hex.length >= 2) {
					var x = parseInt(hex.substring(0, 2), 16);
					hex = hex.substring(2, hex.length);
					byteStream[i++] = x;
				}
				var payloadMessage = new Messaging.Message(byteStream);

				payloadMessage.qos = storedMessage.payloadMessage.qos;
				payloadMessage.destinationName = storedMessage.payloadMessage.destinationName;
				if (storedMessage.payloadMessage.duplicate)
					payloadMessage.duplicate = true;
				if (storedMessage.payloadMessage.retained)
					payloadMessage.retained = true;
				wireMessage.payloadMessage = payloadMessage;

				break;

			default:
				throw Error(format(ERROR.INVALID_STORED_DATA, [key, value]));
		}

		if (key.indexOf("Sent:"+this._localKey) == 0) {
			this._sentMessages[wireMessage.messageIdentifier] = wireMessage;
		} else if (key.indexOf("Received:"+this._localKey) == 0) {
			this._receivedMessages[wireMessage.messageIdentifier] = wireMessage;
		}
	};

	ClientImpl.prototype._process_queue = function () {
		var message = null;
		// Process messages in order they were added
		var fifo = this._msg_queue.reverse();

		// Send all queued messages down socket connection
		while ((message = fifo.pop())) {
			this._socket_send(message);
			// Notify listeners that message was successfully sent
			if (this._notify_msg_sent[message]) {
				this._notify_msg_sent[message]();
				delete this._notify_msg_sent[message];
			}
		}
	};

	/**
	 * Expect an ACK response for this message. Add message to the set of in progress
	 * messages and set an unused identifier in this message.
	 * @ignore
	 */
	ClientImpl.prototype._requires_ack = function (wireMessage) {
		var messageCount = Object.keys(this._sentMessages).length;
		if (messageCount > this.maxMessageIdentifier)
			throw Error ("Too many messages:"+messageCount);

		while(this._sentMessages[this._message_identifier] !== undefined) {
			this._message_identifier++;
		}
		wireMessage.messageIdentifier = this._message_identifier;
		this._sentMessages[wireMessage.messageIdentifier] = wireMessage;
		if (wireMessage.type === MESSAGE_TYPE.PUBLISH) {
			this.store("Sent:", wireMessage);
		}
		if (this._message_identifier === this.maxMessageIdentifier) {
			this._message_identifier = 1;
		}
	};

	/**
	 * Called when the underlying websocket has been opened.
	 * @ignore
	 */
	ClientImpl.prototype._on_socket_open = function () {
		// Create the CONNECT message object.
		var wireMessage = new WireMessage(MESSAGE_TYPE.CONNECT, this.connectOptions);
		wireMessage.clientId = this.clientId;
		this._socket_send(wireMessage);
	};

	/**
	 * Called when the underlying websocket has received a complete packet.
	 * @ignore
	 */
	ClientImpl.prototype._on_socket_message = function (event) {
		this._trace("Client._on_socket_message", event.data);
		// Reset the receive ping timer, we now have evidence the server is alive.
		this.receivePinger.reset();
		var messages = this._deframeMessages(event.data);
		for (var i = 0; i < messages.length; i+=1) {
			this._handleMessage(messages[i]);
		}
	}

	ClientImpl.prototype._deframeMessages = function(data) {
		var byteArray = new Uint8Array(data);
		if (this.receiveBuffer) {
			var newData = new Uint8Array(this.receiveBuffer.length+byteArray.length);
			newData.set(this.receiveBuffer);
			newData.set(byteArray,this.receiveBuffer.length);
			byteArray = newData;
			delete this.receiveBuffer;
		}
		try {
			var offset = 0;
			var messages = [];
			while(offset < byteArray.length) {
				var result = decodeMessage(byteArray,offset);
				var wireMessage = result[0];
				offset = result[1];
				if (wireMessage !== null) {
					messages.push(wireMessage);
				} else {
					break;
				}
			}
			if (offset < byteArray.length) {
				this.receiveBuffer = byteArray.subarray(offset);
			}
		} catch (error) {
			this._disconnected(ERROR.INTERNAL_ERROR.code , format(ERROR.INTERNAL_ERROR, [error.message]));
			return;
		}
		return messages;
	}

	ClientImpl.prototype._handleMessage = function(wireMessage) {

		this._trace("Client._handleMessage", wireMessage);

		try {
			switch(wireMessage.type) {
				case MESSAGE_TYPE.CONNACK:
					this._connectTimeout.cancel();

					// If we have started using clean session then clear up the local state.
					if (this.connectOptions.cleanSession) {
						for (key in this._sentMessages) {
							var sentMessage = this._sentMessages[key];
							localStorage.removeItem("Sent:"+this._localKey+sentMessage.messageIdentifier);
						}
						this._sentMessages = {};

						for (key in this._receivedMessages) {
							var receivedMessage = this._receivedMessages[key];
							localStorage.removeItem("Received:"+this._localKey+receivedMessage.messageIdentifier);
						}
						this._receivedMessages = {};
					}
					// Client connected and ready for business.
					if (wireMessage.returnCode === 0) {
						this.connected = true;
						// Jump to the end of the list of uris and stop looking for a good host.
						if (this.connectOptions.uris)
							this.hostIndex = this.connectOptions.uris.length;
					} else {
						this._disconnected(ERROR.CONNACK_RETURNCODE.code , format(ERROR.CONNACK_RETURNCODE, [wireMessage.returnCode, CONNACK_RC[wireMessage.returnCode]]));
						break;
					}

					// Resend messages.
					var sequencedMessages = new Array();
					for (var msgId in this._sentMessages) {
						if (this._sentMessages.hasOwnProperty(msgId))
							sequencedMessages.push(this._sentMessages[msgId]);
					}

					// Sort sentMessages into the original sent order.
					var sequencedMessages = sequencedMessages.sort(function(a,b) {return a.sequence - b.sequence;} );
					for (var i=0, len=sequencedMessages.length; i<len; i++) {
						var sentMessage = sequencedMessages[i];
						if (sentMessage.type == MESSAGE_TYPE.PUBLISH && sentMessage.pubRecReceived) {
							var pubRelMessage = new WireMessage(MESSAGE_TYPE.PUBREL, {messageIdentifier:sentMessage.messageIdentifier});
							this._schedule_message(pubRelMessage);
						} else {
							this._schedule_message(sentMessage);
						};
					}

					// Execute the connectOptions.onSuccess callback if there is one.
					if (this.connectOptions.onSuccess) {
						this.connectOptions.onSuccess({invocationContext:this.connectOptions.invocationContext});
					}

					// Process all queued messages now that the connection is established.
					this._process_queue();
					break;

				case MESSAGE_TYPE.PUBLISH:
					this._receivePublish(wireMessage);
					break;

				case MESSAGE_TYPE.PUBACK:
					var sentMessage = this._sentMessages[wireMessage.messageIdentifier];
					// If this is a re flow of a PUBACK after we have restarted receivedMessage will not exist.
					if (sentMessage) {
						delete this._sentMessages[wireMessage.messageIdentifier];
						localStorage.removeItem("Sent:"+this._localKey+wireMessage.messageIdentifier);
						if (this.onMessageDelivered)
							this.onMessageDelivered(sentMessage.payloadMessage);
					}
					break;

				case MESSAGE_TYPE.PUBREC:
					var sentMessage = this._sentMessages[wireMessage.messageIdentifier];
					// If this is a re flow of a PUBREC after we have restarted receivedMessage will not exist.
					if (sentMessage) {
						sentMessage.pubRecReceived = true;
						var pubRelMessage = new WireMessage(MESSAGE_TYPE.PUBREL, {messageIdentifier:wireMessage.messageIdentifier});
						this.store("Sent:", sentMessage);
						this._schedule_message(pubRelMessage);
					}
					break;

				case MESSAGE_TYPE.PUBREL:
					var receivedMessage = this._receivedMessages[wireMessage.messageIdentifier];
					localStorage.removeItem("Received:"+this._localKey+wireMessage.messageIdentifier);
					// If this is a re flow of a PUBREL after we have restarted receivedMessage will not exist.
					if (receivedMessage) {
						this._receiveMessage(receivedMessage);
						delete this._receivedMessages[wireMessage.messageIdentifier];
					}
					// Always flow PubComp, we may have previously flowed PubComp but the server lost it and restarted.
					pubCompMessage = new WireMessage(MESSAGE_TYPE.PUBCOMP, {messageIdentifier:wireMessage.messageIdentifier});
					this._schedule_message(pubCompMessage);


					break;

				case MESSAGE_TYPE.PUBCOMP:
					var sentMessage = this._sentMessages[wireMessage.messageIdentifier];
					delete this._sentMessages[wireMessage.messageIdentifier];
					localStorage.removeItem("Sent:"+this._localKey+wireMessage.messageIdentifier);
					if (this.onMessageDelivered)
						this.onMessageDelivered(sentMessage.payloadMessage);
					break;

				case MESSAGE_TYPE.SUBACK:
					var sentMessage = this._sentMessages[wireMessage.messageIdentifier];
					if (sentMessage) {
						if(sentMessage.timeOut)
							sentMessage.timeOut.cancel();
						if (sentMessage.callback) {
							sentMessage.callback();
						}
						delete this._sentMessages[wireMessage.messageIdentifier];
					}
					break;

				case MESSAGE_TYPE.UNSUBACK:
					var sentMessage = this._sentMessages[wireMessage.messageIdentifier];
					if (sentMessage) {
						if (sentMessage.timeOut)
							sentMessage.timeOut.cancel();
						if (sentMessage.callback) {
							sentMessage.callback();
						}
						delete this._sentMessages[wireMessage.messageIdentifier];
					}

					break;

				case MESSAGE_TYPE.PINGRESP:
					/* The sendPinger or receivePinger may have sent a ping, the receivePinger has already been reset. */
					this.sendPinger.reset();
					break;

				case MESSAGE_TYPE.DISCONNECT:
					// Clients do not expect to receive disconnect packets.
					this._disconnected(ERROR.INVALID_MQTT_MESSAGE_TYPE.code , format(ERROR.INVALID_MQTT_MESSAGE_TYPE, [wireMessage.type]));
					break;

				default:
					this._disconnected(ERROR.INVALID_MQTT_MESSAGE_TYPE.code , format(ERROR.INVALID_MQTT_MESSAGE_TYPE, [wireMessage.type]));
			};
		} catch (error) {
			this._disconnected(ERROR.INTERNAL_ERROR.code , format(ERROR.INTERNAL_ERROR, [error.message]));
			return;
		}
	};

	/** @ignore */
	ClientImpl.prototype._on_socket_error = function (error) {
		this._disconnected(ERROR.SOCKET_ERROR.code , format(ERROR.SOCKET_ERROR, [error.data]));
	};

	/** @ignore */
	ClientImpl.prototype._on_socket_close = function () {
		this._disconnected(ERROR.SOCKET_CLOSE.code , format(ERROR.SOCKET_CLOSE));
	};

	/** @ignore */
	ClientImpl.prototype._socket_send = function (wireMessage) {

		if (wireMessage.type == 1) {
			var wireMessageMasked = this._traceMask(wireMessage, "password");
			this._trace("Client._socket_send", wireMessageMasked);
		}
		else this._trace("Client._socket_send", wireMessage);

		this.socket.send(wireMessage.encode());
		/* We have proved to the server we are alive. */
		this.sendPinger.reset();
	};

	/** @ignore */
	ClientImpl.prototype._receivePublish = function (wireMessage) {
		switch(wireMessage.payloadMessage.qos) {
			case "undefined":
			case 0:
				this._receiveMessage(wireMessage);
				break;

			case 1:
				var pubAckMessage = new WireMessage(MESSAGE_TYPE.PUBACK, {messageIdentifier:wireMessage.messageIdentifier});
				this._schedule_message(pubAckMessage);
				this._receiveMessage(wireMessage);
				break;

			case 2:
				this._receivedMessages[wireMessage.messageIdentifier] = wireMessage;
				this.store("Received:", wireMessage);
				var pubRecMessage = new WireMessage(MESSAGE_TYPE.PUBREC, {messageIdentifier:wireMessage.messageIdentifier});
				this._schedule_message(pubRecMessage);

				break;

			default:
				throw Error("Invaild qos="+wireMmessage.payloadMessage.qos);
		};
	};

	/** @ignore */
	ClientImpl.prototype._receiveMessage = function (wireMessage) {
		if (this.onMessageArrived) {
			this.onMessageArrived(wireMessage.payloadMessage);
		}
	};

	/**
	 * Client has disconnected either at its own request or because the server
	 * or network disconnected it. Remove all non-durable state.
	 * @param {errorCode} [number] the error number.
	 * @param {errorText} [string] the error text.
	 * @ignore
	 */
	ClientImpl.prototype._disconnected = function (errorCode, errorText) {
		this._trace("Client._disconnected", errorCode, errorText);

		this.sendPinger.cancel();
		this.receivePinger.cancel();
		if (this._connectTimeout)
			this._connectTimeout.cancel();
		// Clear message buffers.
		this._msg_queue = [];
		this._notify_msg_sent = {};

		if (this.socket) {
			// Cancel all socket callbacks so that they cannot be driven again by this socket.
			this.socket.onopen = null;
			this.socket.onmessage = null;
			this.socket.onerror = null;
			this.socket.onclose = null;
			if (this.socket.readyState === 1)
				this.socket.close();
			delete this.socket;
		}

		if (this.connectOptions.uris && this.hostIndex < this.connectOptions.uris.length-1) {
			// Try the next host.
			this.hostIndex++;
			this._doConnect(this.connectOptions.uris[this.hostIndex]);

		} else {

			if (errorCode === undefined) {
				errorCode = ERROR.OK.code;
				errorText = format(ERROR.OK);
			}

			// Run any application callbacks last as they may attempt to reconnect and hence create a new socket.
			if (this.connected) {
				this.connected = false;
				// Execute the connectionLostCallback if there is one, and we were connected.
				if (this.onConnectionLost)
					this.onConnectionLost({errorCode:errorCode, errorMessage:errorText});
			} else {
				// Otherwise we never had a connection, so indicate that the connect has failed.
				if(this.connectOptions.onFailure)
					this.connectOptions.onFailure({invocationContext:this.connectOptions.invocationContext, errorCode:errorCode, errorMessage:errorText});
			}
		}
	};

	/** @ignore */
	ClientImpl.prototype._trace = function () {
		if ( this._traceBuffer !== null ) {
			for (var i = 0, max = arguments.length; i < max; i++) {
				if ( this._traceBuffer.length == this._MAX_TRACE_ENTRIES ) {
					this._traceBuffer.shift();
				}
				if (i === 0) this._traceBuffer.push(arguments[i]);
				else if (typeof arguments[i] === "undefined" ) this._traceBuffer.push(arguments[i]);
				else this._traceBuffer.push("  "+JSON.stringify(arguments[i]));
			};
		};
	};

	/** @ignore */
	ClientImpl.prototype._traceMask = function (traceObject, masked) {
		var traceObjectMasked = {};
		for (var attr in traceObject) {
			if (traceObject.hasOwnProperty(attr)) {
				if (attr == masked)
					traceObjectMasked[attr] = "******";
				else
					traceObjectMasked[attr] = traceObject[attr];
			}
		}
		return traceObjectMasked;
	};

	// ------------------------------------------------------------------------
	// Public Programming interface.
	// ------------------------------------------------------------------------

	/**
	 * The JavaScript application communicates to the server using a {@link Messaging.Client} object.
	 * <p>
	 * Most applications will create just one Client object and then call its connect() method,
	 * however applications can create more than one Client object if they wish.
	 * In this case the combination of host, port and clientId attributes must be different for each Client object.
	 * <p>
	 * The send, subscribe and unsubscribe methods are implemented as asynchronous JavaScript methods
	 * (even though the underlying protocol exchange might be synchronous in nature).
	 * This means they signal their completion by calling back to the application,
	 * via Success or Failure callback functions provided by the application on the method in question.
	 * Such callbacks are called at most once per method invocation and do not persist beyond the lifetime
	 * of the script that made the invocation.
	 * <p>
	 * In contrast there are some callback functions, most notably <i>onMessageArrived</i>,
	 * that are defined on the {@link Messaging.Client} object.
	 * These may get called multiple times, and aren't directly related to specific method invocations made by the client.
	 *
	 * @name Messaging.Client
	 *
	 * @constructor
	 *
	 * @param {string} host - the address of the messaging server, as a fully qualified WebSocket URI, as a DNS name or dotted decimal IP address.
	 * @param {number} port - the port number to connect to - only required if host is not a URI
	 * @param {string} path - the path on the host to connect to - only used if host is not a URI. Default: '/mqtt'.
	 * @param {string} clientId - the Messaging client identifier, between 1 and 23 characters in length.
	 *
	 * @property {string} host - <i>read only</i> the server's DNS hostname or dotted decimal IP address.
	 * @property {number} port - <i>read only</i> the server's port.
	 * @property {string} path - <i>read only</i> the server's path.
	 * @property {string} clientId - <i>read only</i> used when connecting to the server.
	 * @property {function} onConnectionLost - called when a connection has been lost.
	 *                            after a connect() method has succeeded.
	 *                            Establish the call back used when a connection has been lost. The connection may be
	 *                            lost because the client initiates a disconnect or because the server or network
	 *                            cause the client to be disconnected. The disconnect call back may be called without
	 *                            the connectionComplete call back being invoked if, for example the client fails to
	 *                            connect.
	 *                            A single response object parameter is passed to the onConnectionLost callback containing the following fields:
	 *                            <ol>
	 *                            <li>errorCode
	 *                            <li>errorMessage
	 *                            </ol>
	 * @property {function} onMessageDelivered called when a message has been delivered.
	 *                            All processing that this Client will ever do has been completed. So, for example,
	 *                            in the case of a Qos=2 message sent by this client, the PubComp flow has been received from the server
	 *                            and the message has been removed from persistent storage before this callback is invoked.
	 *                            Parameters passed to the onMessageDelivered callback are:
	 *                            <ol>
	 *                            <li>{@link Messaging.Message} that was delivered.
	 *                            </ol>
	 * @property {function} onMessageArrived called when a message has arrived in this Messaging.client.
	 *                            Parameters passed to the onMessageArrived callback are:
	 *                            <ol>
	 *                            <li>{@link Messaging.Message} that has arrived.
	 *                            </ol>
	 */
	var Client = function (host, port, path, clientId) {

		var uri;

		if (typeof host !== "string")
			throw new Error(format(ERROR.INVALID_TYPE, [typeof host, "host"]));

		if (arguments.length == 2) {
			// host: must be full ws:// uri
			// port: clientId
			clientId = port;
			uri = host;
			var match = uri.match(/^(wss?):\/\/((\[(.+)\])|([^\/]+?))(:(\d+))?(\/.*)$/);
			if (match) {
				host = match[4]||match[2];
				port = parseInt(match[7]);
				path = match[8];
			} else {
				throw new Error(format(ERROR.INVALID_ARGUMENT,[host,"host"]));
			}
		} else {
			if (arguments.length == 3) {
				clientId = path;
				path = "/mqtt";
			}
			if (typeof port !== "number" || port < 0)
				throw new Error(format(ERROR.INVALID_TYPE, [typeof port, "port"]));
			if (typeof path !== "string")
				throw new Error(format(ERROR.INVALID_TYPE, [typeof path, "path"]));

			var ipv6 = (host.indexOf(":") != -1);
			uri = "ws://"+(ipv6?"["+host+"]":host)+":"+port+path;
		}

		var clientIdLength = 0;
		for (var i = 0; i<clientId.length; i++) {
			var charCode = clientId.charCodeAt(i);
			if (0xD800 <= charCode && charCode <= 0xDBFF)  {
				i++; // Surrogate pair.
			}
			clientIdLength++;
		}
		if (typeof clientId !== "string" || clientIdLength < 1 | clientIdLength > 23)
			throw new Error(format(ERROR.INVALID_ARGUMENT, [clientId, "clientId"]));

		var client = new ClientImpl(uri, host, port, path, clientId);
		this._getHost =  function() { return host; };
		this._setHost = function() { throw new Error(format(ERROR.UNSUPPORTED_OPERATION)); };

		this._getPort = function() { return port; };
		this._setPort = function() { throw new Error(format(ERROR.UNSUPPORTED_OPERATION)); };

		this._getPath = function() { return path; };
		this._setPath = function() { throw new Error(format(ERROR.UNSUPPORTED_OPERATION)); };

		this._getURI = function() { return uri; };
		this._setURI = function() { throw new Error(format(ERROR.UNSUPPORTED_OPERATION)); };

		this._getClientId = function() { return client.clientId; };
		this._setClientId = function() { throw new Error(format(ERROR.UNSUPPORTED_OPERATION)); };

		this._getOnConnectionLost = function() { return client.onConnectionLost; };
		this._setOnConnectionLost = function(newOnConnectionLost) {
			if (typeof newOnConnectionLost === "function")
				client.onConnectionLost = newOnConnectionLost;
			else
				throw new Error(format(ERROR.INVALID_TYPE, [typeof newOnConnectionLost, "onConnectionLost"]));
		};

		this._getOnMessageDelivered = function() { return client.onMessageDelivered; };
		this._setOnMessageDelivered = function(newOnMessageDelivered) {
			if (typeof newOnMessageDelivered === "function")
				client.onMessageDelivered = newOnMessageDelivered;
			else
				throw new Error(format(ERROR.INVALID_TYPE, [typeof newOnMessageDelivered, "onMessageDelivered"]));
		};

		this._getOnMessageArrived = function() { return client.onMessageArrived; };
		this._setOnMessageArrived = function(newOnMessageArrived) {
			if (typeof newOnMessageArrived === "function")
				client.onMessageArrived = newOnMessageArrived;
			else
				throw new Error(format(ERROR.INVALID_TYPE, [typeof newOnMessageArrived, "onMessageArrived"]));
		};

		/**
		 * Connect this Messaging client to its server.
		 *
		 * @name Messaging.Client#connect
		 * @function
		 * @param {Object} connectOptions - attributes used with the connection.
		 * @param {number} connectOptions.timeout - If the connect has not succeeded within this
		 *                    number of seconds, it is deemed to have failed.
		 *                    The default is 30 seconds.
		 * @param {string} connectOptions.userName - Authentication username for this connection.
		 * @param {string} connectOptions.password - Authentication password for this connection.
		 * @param {Messaging.Message} connectOptions.willMessage - sent by the server when the client
		 *                    disconnects abnormally.
		 * @param {Number} connectOptions.keepAliveInterval - the server disconnects this client if
		 *                    there is no activity for this number of seconds.
		 *                    The default value of 60 seconds is assumed if not set.
		 * @param {boolean} connectOptions.cleanSession - if true(default) the client and server
		 *                    persistent state is deleted on successful connect.
		 * @param {boolean} connectOptions.useSSL - if present and true, use an SSL Websocket connection.
		 * @param {object} connectOptions.invocationContext - passed to the onSuccess callback or onFailure callback.
		 * @param {function} connectOptions.onSuccess - called when the connect acknowledgement
		 *                    has been received from the server.
		 * A single response object parameter is passed to the onSuccess callback containing the following fields:
		 * <ol>
		 * <li>invocationContext as passed in to the onSuccess method in the connectOptions.
		 * </ol>
		 * @config {function} [onFailure] called when the connect request has failed or timed out.
		 * A single response object parameter is passed to the onFailure callback containing the following fields:
		 * <ol>
		 * <li>invocationContext as passed in to the onFailure method in the connectOptions.
		 * <li>errorCode a number indicating the nature of the error.
		 * <li>errorMessage text describing the error.
		 * </ol>
		 * @config {Array} [hosts] If present this contains either a set of hostnames or fully qualified
		 * WebSocket URIs (ws://example.com:1883/mqtt), that are tried in order in place
		 * of the host and port paramater on the construtor. The hosts are tried one at at time in order until
		 * one of then succeeds.
		 * @config {Array} [ports] If present the set of ports matching the hosts. If hosts contains URIs, this property
		 * is not used.
		 * @throws {InvalidState} if the client is not in disconnected state. The client must have received connectionLost
		 * or disconnected before calling connect for a second or subsequent time.
		 */
		this.connect = function (connectOptions) {
			connectOptions = connectOptions || {} ;
			validate(connectOptions,  {timeout:"number",
				userName:"string",
				password:"string",
				willMessage:"object",
				keepAliveInterval:"number",
				cleanSession:"boolean",
				useSSL:"boolean",
				invocationContext:"object",
				onSuccess:"function",
				onFailure:"function",
				hosts:"object",
				ports:"object"});

			// If no keep alive interval is set, assume 60 seconds.
			if (connectOptions.keepAliveInterval === undefined)
				connectOptions.keepAliveInterval = 60;

			if (connectOptions.willMessage) {
				if (!(connectOptions.willMessage instanceof Message))
					throw new Error(format(ERROR.INVALID_TYPE, [connectOptions.willMessage, "connectOptions.willMessage"]));
				// The will message must have a payload that can be represented as a string.
				// Cause the willMessage to throw an exception if this is not the case.
				connectOptions.willMessage.stringPayload;

				if (typeof connectOptions.willMessage.destinationName === "undefined")
					throw new Error(format(ERROR.INVALID_TYPE, [typeof connectOptions.willMessage.destinationName, "connectOptions.willMessage.destinationName"]));
			}
			if (typeof connectOptions.cleanSession === "undefined")
				connectOptions.cleanSession = true;
			if (connectOptions.hosts) {

				if (!(connectOptions.hosts instanceof Array) )
					throw new Error(format(ERROR.INVALID_ARGUMENT, [connectOptions.hosts, "connectOptions.hosts"]));
				if (connectOptions.hosts.length <1 )
					throw new Error(format(ERROR.INVALID_ARGUMENT, [connectOptions.hosts, "connectOptions.hosts"]));

				var usingURIs = false;
				for (var i = 0; i<connectOptions.hosts.length; i++) {
					if (typeof connectOptions.hosts[i] !== "string")
						throw new Error(format(ERROR.INVALID_TYPE, [typeof connectOptions.hosts[i], "connectOptions.hosts["+i+"]"]));
					if (/^(wss?):\/\/((\[(.+)\])|([^\/]+?))(:(\d+))?(\/.*)$/.test(connectOptions.hosts[i])) {
						if (i == 0) {
							usingURIs = true;
						} else if (!usingURIs) {
							throw new Error(format(ERROR.INVALID_ARGUMENT, [connectOptions.hosts[i], "connectOptions.hosts["+i+"]"]));
						}
					} else if (usingURIs) {
						throw new Error(format(ERROR.INVALID_ARGUMENT, [connectOptions.hosts[i], "connectOptions.hosts["+i+"]"]));
					}
				}

				if (!usingURIs) {
					if (!connectOptions.ports)
						throw new Error(format(ERROR.INVALID_ARGUMENT, [connectOptions.ports, "connectOptions.ports"]));
					if (!(connectOptions.ports instanceof Array) )
						throw new Error(format(ERROR.INVALID_ARGUMENT, [connectOptions.ports, "connectOptions.ports"]));
					if (connectOptions.hosts.length != connectOptions.ports.length)
						throw new Error(format(ERROR.INVALID_ARGUMENT, [connectOptions.ports, "connectOptions.ports"]));

					connectOptions.uris = [];

					for (var i = 0; i<connectOptions.hosts.length; i++) {
						if (typeof connectOptions.ports[i] !== "number" || connectOptions.ports[i] < 0)
							throw new Error(format(ERROR.INVALID_TYPE, [typeof connectOptions.ports[i], "connectOptions.ports["+i+"]"]));
						var host = connectOptions.hosts[i];
						var port = connectOptions.ports[i];

						var ipv6 = (host.indexOf(":") != -1);
						uri = "ws://"+(ipv6?"["+host+"]":host)+":"+port+path;
						connectOptions.uris.push(uri);
					}
				} else {
					connectOptions.uris = connectOptions.hosts;
				}
			}

			client.connect(connectOptions);
		};

		/**
		 * Subscribe for messages, request receipt of a copy of messages sent to the destinations described by the filter.
		 *
		 * @name Messaging.Client#subscribe
		 * @function
		 * @param {string} filter describing the destinations to receive messages from.
		 * <br>
		 * @param {object} subscribeOptions - used to control the subscription
		 *
		 * @param {number} subscribeOptions.qos - the maiximum qos of any publications sent
		 *                                  as a result of making this subscription.
		 * @param {object} subscribeOptions.invocationContext - passed to the onSuccess callback
		 *                                  or onFailure callback.
		 * @param {function} subscribeOptions.onSuccess - called when the subscribe acknowledgement
		 *                                  has been received from the server.
		 *                                  A single response object parameter is passed to the onSuccess callback containing the following fields:
		 *                                  <ol>
		 *                                  <li>invocationContext if set in the subscribeOptions.
		 *                                  </ol>
		 * @param {function} subscribeOptions.onFailure - called when the subscribe request has failed or timed out.
		 *                                  A single response object parameter is passed to the onFailure callback containing the following fields:
		 *                                  <ol>
		 *                                  <li>invocationContext - if set in the subscribeOptions.
		 *                                  <li>errorCode - a number indicating the nature of the error.
		 *                                  <li>errorMessage - text describing the error.
		 *                                  </ol>
		 * @param {number} subscribeOptions.timeout - which, if present, determines the number of
		 *                                  seconds after which the onFailure calback is called.
		 *                                  The presence of a timeout does not prevent the onSuccess
		 *                                  callback from being called when the subscribe completes.
		 * @throws {InvalidState} if the client is not in connected state.
		 */
		this.subscribe = function (filter, subscribeOptions) {
			if (typeof filter !== "string")
				throw new Error("Invalid argument:"+filter);
			subscribeOptions = subscribeOptions || {} ;
			validate(subscribeOptions,  {qos:"number",
				invocationContext:"object",
				onSuccess:"function",
				onFailure:"function",
				timeout:"number"
			});
			if (subscribeOptions.timeout && !subscribeOptions.onFailure)
				throw new Error("subscribeOptions.timeout specified with no onFailure callback.");
			if (typeof subscribeOptions.qos !== "undefined"
					&& !(subscribeOptions.qos === 0 || subscribeOptions.qos === 1 || subscribeOptions.qos === 2 ))
				throw new Error(format(ERROR.INVALID_ARGUMENT, [subscribeOptions.qos, "subscribeOptions.qos"]));
			client.subscribe(filter, subscribeOptions);
		};

		/**
		 * Unsubscribe for messages, stop receiving messages sent to destinations described by the filter.
		 *
		 * @name Messaging.Client#unsubscribe
		 * @function
		 * @param {string} filter - describing the destinations to receive messages from.
		 * @param {object} unsubscribeOptions - used to control the subscription
		 * @param {object} unsubscribeOptions.invocationContext - passed to the onSuccess callback
		 or onFailure callback.
		 * @param {function} unsubscribeOptions.onSuccess - called when the unsubscribe acknowledgement has been received from the server.
		 *                                    A single response object parameter is passed to the
		 *                                    onSuccess callback containing the following fields:
		 *                                    <ol>
		 *                                    <li>invocationContext - if set in the unsubscribeOptions.
		 *                                    </ol>
		 * @param {function} unsubscribeOptions.onFailure called when the unsubscribe request has failed or timed out.
		 *                                    A single response object parameter is passed to the onFailure callback containing the following fields:
		 *                                    <ol>
		 *                                    <li>invocationContext - if set in the unsubscribeOptions.
		 *                                    <li>errorCode - a number indicating the nature of the error.
		 *                                    <li>errorMessage - text describing the error.
		 *                                    </ol>
		 * @param {number} unsubscribeOptions.timeout - which, if present, determines the number of seconds
		 *                                    after which the onFailure callback is called. The presence of
		 *                                    a timeout does not prevent the onSuccess callback from being
		 *                                    called when the unsubscribe completes
		 * @throws {InvalidState} if the client is not in connected state.
		 */
		this.unsubscribe = function (filter, unsubscribeOptions) {
			if (typeof filter !== "string")
				throw new Error("Invalid argument:"+filter);
			unsubscribeOptions = unsubscribeOptions || {} ;
			validate(unsubscribeOptions,  {invocationContext:"object",
				onSuccess:"function",
				onFailure:"function",
				timeout:"number"
			});
			if (unsubscribeOptions.timeout && !unsubscribeOptions.onFailure)
				throw new Error("unsubscribeOptions.timeout specified with no onFailure callback.");
			client.unsubscribe(filter, unsubscribeOptions);
		};

		/**
		 * Send a message to the consumers of the destination in the Message.
		 *
		 * @name Messaging.Client#send
		 * @function
		 * @param {Messaging.Message} message to send.

		 * @throws {InvalidState} if the client is not connected.
		 */
		this.send = function (message) {
			if (!(message instanceof Message))
				throw new Error("Invalid argument:"+typeof message);
			if (typeof message.destinationName === "undefined")
				throw new Error("Invalid parameter Message.destinationName:"+message.destinationName);

			client.send(message);
		};

		/**
		 * Normal disconnect of this Messaging client from its server.
		 *
		 * @name Messaging.Client#disconnect
		 * @function
		 * @throws {InvalidState} if the client is already disconnected.
		 */
		this.disconnect = function () {
			client.disconnect();
		};

		/**
		 * Get the contents of the trace log.
		 *
		 * @name Messaging.Client#getTraceLog
		 * @function
		 * @return {Object[]} tracebuffer containing the time ordered trace records.
		 */
		this.getTraceLog = function () {
			return client.getTraceLog();
		}

		/**
		 * Start tracing.
		 *
		 * @name Messaging.Client#startTrace
		 * @function
		 */
		this.startTrace = function () {
			client.startTrace();
		};

		/**
		 * Stop tracing.
		 *
		 * @name Messaging.Client#stopTrace
		 * @function
		 */
		this.stopTrace = function () {
			client.stopTrace();
		};
	};

	Client.prototype = {
		get host() { return this._getHost(); },
		set host(newHost) { this._setHost(newHost); },

		get port() { return this._getPort(); },
		set port(newPort) { this._setPort(newPort); },

		get path() { return this._getPath(); },
		set path(newPath) { this._setPath(newPath); },

		get clientId() { return this._getClientId(); },
		set clientId(newClientId) { this._setClientId(newClientId); },

		get onConnectionLost() { return this._getOnConnectionLost(); },
		set onConnectionLost(newOnConnectionLost) { this._setOnConnectionLost(newOnConnectionLost); },

		get onMessageDelivered() { return this._getOnMessageDelivered(); },
		set onMessageDelivered(newOnMessageDelivered) { this._setOnMessageDelivered(newOnMessageDelivered); },

		get onMessageArrived() { return this._getOnMessageArrived(); },
		set onMessageArrived(newOnMessageArrived) { this._setOnMessageArrived(newOnMessageArrived); }
	};

	/**
	 * An application message, sent or received.
	 * <p>
	 * All attributes may be null, which implies the default values.
	 *
	 * @name Messaging.Message
	 * @constructor
	 * @param {String|ArrayBuffer} payload The message data to be sent.
	 * <p>
	 * @property {string} payloadString <i>read only</i> The payload as a string if the payload consists of valid UTF-8 characters.
	 * @property {ArrayBuffer} payloadBytes <i>read only</i> The payload as an ArrayBuffer.
	 * <p>
	 * @property {string} destinationName <b>mandatory</b> The name of the destination to which the message is to be sent
	 *                    (for messages about to be sent) or the name of the destination from which the message has been received.
	 *                    (for messages received by the onMessage function).
	 * <p>
	 * @property {number} qos The Quality of Service used to deliver the message.
	 * <dl>
	 *     <dt>0 Best effort (default).
	 *     <dt>1 At least once.
	 *     <dt>2 Exactly once.
	 * </dl>
	 * <p>
	 * @property {Boolean} retained If true, the message is to be retained by the server and delivered
	 *                     to both current and future subscriptions.
	 *                     If false the server only delivers the message to current subscribers, this is the default for new Messages.
	 *                     A received message has the retained boolean set to true if the message was published
	 *                     with the retained boolean set to true
	 *                     and the subscrption was made after the message has been published.
	 * <p>
	 * @property {Boolean} duplicate <i>read only</i> If true, this message might be a duplicate of one which has already been received.
	 *                     This is only set on messages received from the server.
	 *
	 */
	var Message = function (newPayload) {
		var payload;
		if (   typeof newPayload === "string"
				|| newPayload instanceof ArrayBuffer
				|| newPayload instanceof Int8Array
				|| newPayload instanceof Uint8Array
				|| newPayload instanceof Int16Array
				|| newPayload instanceof Uint16Array
				|| newPayload instanceof Int32Array
				|| newPayload instanceof Uint32Array
				|| newPayload instanceof Float32Array
				|| newPayload instanceof Float64Array
		   ) {
			   payload = newPayload;
		   } else {
			   throw (format(ERROR.INVALID_ARGUMENT, [newPayload, "newPayload"]));
		   }

		this._getPayloadString = function () {
			if (typeof payload === "string")
				return payload;
			else
				return parseUTF8(payload, 0, payload.length);
		};

		this._getPayloadBytes = function() {
			if (typeof payload === "string") {
				var buffer = new ArrayBuffer(UTF8Length(payload));
				var byteStream = new Uint8Array(buffer);
				stringToUTF8(payload, byteStream, 0);

				return byteStream;
			} else {
				return payload;
			};
		};

		var destinationName = undefined;
		this._getDestinationName = function() { return destinationName; };
		this._setDestinationName = function(newDestinationName) {
			if (typeof newDestinationName === "string")
				destinationName = newDestinationName;
			else
				throw new Error(format(ERROR.INVALID_ARGUMENT, [newDestinationName, "newDestinationName"]));
		};

		var qos = 0;
		this._getQos = function() { return qos; };
		this._setQos = function(newQos) {
			if (newQos === 0 || newQos === 1 || newQos === 2 )
				qos = newQos;
			else
				throw new Error("Invalid argument:"+newQos);
		};

		var retained = false;
		this._getRetained = function() { return retained; };
		this._setRetained = function(newRetained) {
			if (typeof newRetained === "boolean")
				retained = newRetained;
			else
				throw new Error(format(ERROR.INVALID_ARGUMENT, [newRetained, "newRetained"]));
		};

		var duplicate = false;
		this._getDuplicate = function() { return duplicate; };
		this._setDuplicate = function(newDuplicate) { duplicate = newDuplicate; };
	};

	Message.prototype = {
		get payloadString() { return this._getPayloadString(); },
		get payloadBytes() { return this._getPayloadBytes(); },

		get destinationName() { return this._getDestinationName(); },
		set destinationName(newDestinationName) { this._setDestinationName(newDestinationName); },

		get qos() { return this._getQos(); },
		set qos(newQos) { this._setQos(newQos); },

		get retained() { return this._getRetained(); },
		set retained(newRetained) { this._setRetained(newRetained); },

		get duplicate() { return this._getDuplicate(); },
		set duplicate(newDuplicate) { this._setDuplicate(newDuplicate); }
	};

	// Module contents.
	return {
		Client: Client,
			Message: Message
	};
})(window);