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标题: OpenHarmony/HarmonyOS 应用开发(十二、paho-mqtt的mqtt客户端库移植) [打印本页]

作者: csdn-qq8864 时间: 2024-3-6 11:01
标题: OpenHarmony/HarmonyOS 应用开发(十二、paho-mqtt的mqtt客户端库移植)
[md]> PAHO MQTT 是 Eclipse Foundation 的一个开源项目，提供了用于 MQTT 协议的客户端库。这个库为使用 MQTT 协议的应用程序提供了丰富的功能和灵活性。轻量级mqtt服务器mosquitto也是其中有名的一个开源项目。

PAHO MQTT介绍
项目开源地址：GitHub - eclipse/paho.mqtt.javascript: paho.mqtt.javascript

PAHO MQTT 客户端库支持多种平台，包括 Java、JavaScript、C、Python 等，使得开发者可以在不同的环境中使用相同的客户端代码来实现 MQTT 通信。

移植后的我的开源仓库地址： https://gitee.com/yyz116/paho-mqtt

已发布到OpenHarmony三方库市场，地址：OpenHarmony三方库中心仓 [仓库地址](https://ohpm.openharmony.cn/#/cn/detail/@yyz116%2Fpaho-mqtt)

以下是 PAHO MQTT 客户端库的一些关键特性：

支持 MQTT 协议的各种版本：PAHO MQTT 客户端库提供了对 MQTT 3.1、3.1.1、5.0 版本的支持，使得开发者可以根据自己的需求选择合适的 MQTT 版本进行通信。

提供丰富的 API：PAHO MQTT 客户端库提供了丰富的 API，包括连接服务器、发布消息、订阅主题、处理消息等，开发者可以灵活地使用这些 API 来实现自己的 MQTT 应用程序。

支持 TLS/SSL 安全连接：PAHO MQTT 客户端库提供了对 TLS/SSL 安全连接的支持，使得 MQTT 通信可以在安全的网络环境下进行。

跨平台支持：PAHO MQTT 客户端库支持多种平台，包括 Java、JavaScript、C、Python 等，使得开发者可以在不同的环境中使用相同的客户端代码来实现 MQTT 通信。

持久化消息：PAHO MQTT 客户端库支持持久化消息，即使客户端断开连接，消息也可以被持久化，确保消息不会丢失。

原库的介绍：The Paho JavaScript Client is an MQTT browser-based client library written in Javascript that uses WebSockets to connect to an MQTT Broker.

原库的这个js库只支持WebSocket通信，本移植后续支持tcp方式通信。

移植后的我的开源仓库地址： https://gitee.com/yyz116/paho-mqtt

已发布到OpenHarmony三方库市场，地址：OpenHarmony三方库中心仓 [仓库地址](https://ohpm.openharmony.cn/#/cn/detail/@yyz116%2Fpaho-mqtt)

**移植过程**
移植参考第三方开源js库移植适配指南，[移植指南](https://blog.csdn.net/yyz_1987/article/details/136037394)

从项目仓库paho.mqtt.javascript下载下来源码，打开paho-mqtt.js文件，首选看到的是以下代码：

```
(function ExportLibrary(root, factory) {
if (typeof exports === 'object' && typeof module === 'object') {
module.exports = factory();
} else if (typeof define === 'function' && define.amd) {
define(factory);
} else if (typeof exports === 'object') {
exports = factory();
} else {
if (typeof root.Paho === 'undefined') {
root.Paho = {};
}
root.Paho.MQTT = factory();
}
})( this,function LibraryFactory() {
// ......});
```

这段代码采用的是UMD (Universal Module Definition) 模块化规范，用于创建一个可以在CommonJS、AMD以及全局变量环境下都能正常加载和使用的JavaScript库。这种写法允许同一段代码在Node.js（CommonJS）、RequireJS（AMD）或非模块化的浏览器环境中运行。

代码结构解释如下：

ExportLibrary函数是UMD的实现部分，它接收两个参数：root和factory。

root通常指向全局对象，在浏览器中是window，在Node.js中是global。

factory是一个函数，当调用时会生成实际的库模块内容。

函数内部根据不同的环境条件执行相应的导出操作：

如果当前环境支持CommonJS（如Node.js），则将工厂函数的结果导出为module.exports。

如果当前环境支持AMD（如RequireJS），则使用define函数定义模块并传入工厂函数。

如果在非模块化环境且检测到exports存在（可能是在某些老版本的CommonJS兼容环境中），直接赋值给exports。

最后一种情况，如果没有上述任何模块系统，就将库挂载到全局对象上，这里是root.Paho.MQTT = factory();，即将factory函数返回的对象作为Paho命名空间下的MQTT属性暴露出去。

最后的括号( function LibraryFactory() { ... } )实际上是立即执行函数表达式（IIFE, Immediately Invoked Function Expression），在这里传递了LibraryFactory函数作为ExportLibrary函数的参数。但在这个示例中，LibraryFactory函数体为空，看起来可能是待填充实际库内容的部分。正常情况下，LibraryFactory应该包含了实际的库实现代码，以便在不同模块环境下正确初始化和导出。

在HarmonyOS的环境中，不存在名为global的全局对象。在浏览器环境中，通常全局对象是window，在Node.js 环境中则是global。然而，在OpenHarmony操作系统中，全局对象的命名可能不同，或者可能不存在类似的全局对象用于在所有代码中共享变量和函数。因此在移植时，这里是需要大刀阔斧的砍掉和修改的。

接下来开始移植，引入OpenHarmony的websocket库，在function LibraryFactory里，实例化websocket客户端实例。在 JavaScript 中，当多个模块 import 同一个模块时，导出的对象会被多次实例化吗？不会的，这是因为：

这是因为模块在 JavaScript 中是单例模式的，意味着无论import多少次，导出的对象都是同一个实例。下面是一个示例，假设有一个名为 MyClass 的类对象在 "myModule.js" 中被定义和导出。

整个代码量不大，很适合学习很适合学和参考。

移植后的完整代码如下：

```
import webSocket from '@ohos.net.webSocket';
function LibraryFactory() {
var ws = webSocket.createWebSocket();
var PahoMQTT = (function(ws) {

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

 var version = "@VERSION@";
 var buildLevel = "@BUILDLEVEL@";
 /**
 * @private
 */
 var localStorage = (function () {
 var data = {};

 return {
 setItem: function (key, item) { data[key] = item; },
 getItem: function (key) { return data[key]; },
 removeItem: function (key) { delete data[key]; },
 };
 })();
 /**
 * 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 (var 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 (var validKey in keys)
 if (keys.hasOwnProperty(validKey))
 errorStr = errorStr + " " + validKey;
 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. Error Message: {0}, Stack trace: {1}" },
 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}." },
 BUFFER_FULL: { code: 18, text: "AMQJS0018E Message buffer is full, maximum buffer size: {0}." },
 };

 /** 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) {
 var field, start;
 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 + part2;
 }
 }
 }
 return text;
 };

 //MQTT protocol and version 6 M Q I s d p 3
 var MqttProtoIdentifierv3 = [0x00, 0x06, 0x4d, 0x51, 0x49, 0x73, 0x64, 0x70, 0x03];
 //MQTT proto/version for 311 4 M Q T T 4
 var MqttProtoIdentifierv4 = [0x00, 0x04, 0x4d, 0x51, 0x54, 0x54, 0x04];

 /**
 * 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 (var 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
 */

 var remLength = 0;
 var topicStrLength = [];
 var destinationNameLength = 0;
 var willMessagePayloadBytes;

 // 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:
 switch (this.mqttVersion) {
 case 3:
 remLength += MqttProtoIdentifierv3.length + 3;
 break;
 case 4:
 remLength += MqttProtoIdentifierv4.length + 3;
 break;
 }

 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.
 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 = UTF8Length(this.topics);
 remLength += topicStrLength + 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 = UTF8Length(this.topics);
 remLength += topicStrLength + 2;
 }
 break;

 case MESSAGE_TYPE.PUBREL:
 first |= 0x02; // Qos = 1;
 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:
 break;
 }

 // 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) {
 switch (this.mqttVersion) {
 case 3:
 byteStream.set(MqttProtoIdentifierv3, pos);
 pos += MqttProtoIdentifierv3.length;
 break;
 case 4:
 byteStream.set(MqttProtoIdentifierv4, pos);
 pos += MqttProtoIdentifierv4.length;
 break;
 }
 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, topicStrLength, byteStream, pos);
 byteStream[pos++] = this.requestedQos;
 }
 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, topicStrLength, 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:
 var connectAcknowledgeFlags = input[pos++];
 if (connectAcknowledgeFlags & 0x01)
 wireMessage.sessionPresent = true;
 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 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.returnCode = input.subarray(pos, endPos);
 break;

 default:
 break;
 }

 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) {
 var 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, keepAliveInterval) {
 this._client = client;
 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("inger.doPing", "Timed out");
 this._client._disconnected(ERROR.PING_TIMEOUT.code, format(ERROR.PING_TIMEOUT));
 } else {
 this.isReset = false;
 this._client._trace("inger.doPing", "send PINGREQ");
 ws.send(pingReq, (err, value) => {
 if (!err) {
 this._client._trace("Message sent successfully");
 } else {
 this._client._trace("Failed to send the message. Err:" + JSON.stringify(err));
 }
 });
 this.timeout = setTimeout(doTimeout(this), this._keepAliveInterval);
 }
 };

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

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

 /**
 * Monitor request completion.
 * @ignore
 */
 var Timeout = function(client, timeoutSeconds, action, args) {
 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() {
 clearTimeout(this.timeout);
 };
 };

 /*
 * Internal implementation of the Websockets MQTT V3.1 client.
 *
 * @name Paho.MQTT.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) {
 this._trace("aho.MQTT.Client", uri, host, port, path, clientId);

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

 // 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 = [];
 this._buffered_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.
 // Load the local state, if any, from the saved version, only restore state relevant to this client.
 for (var 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 = null;
 ClientImpl.prototype.port = null;
 ClientImpl.prototype.path = null;
 ClientImpl.prototype.uri = null;
 ClientImpl.prototype.clientId = null;

 // Messaging Client private instance members.
 ClientImpl.prototype.socket = null;
 /* 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 = null;
 ClientImpl.prototype.hostIndex = null;
 ClientImpl.prototype.onConnected = null;
 ClientImpl.prototype.onConnectionLost = null;
 ClientImpl.prototype.onMessageDelivered = null;
 ClientImpl.prototype.onMessageArrived = null;
 ClientImpl.prototype.traceFunction = null;
 ClientImpl.prototype._msg_queue = null;
 ClientImpl.prototype._buffered_msg_queue = null;
 ClientImpl.prototype._connectTimeout = null;
 /* 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._reconnectInterval = 1; // Reconnect Delay, starts at 1 second
 ClientImpl.prototype._reconnecting = false;
 ClientImpl.prototype._reconnectTimeout = null;
 ClientImpl.prototype.disconnectedPublishing = false;
 ClientImpl.prototype.disconnectedBufferSize = 5000;

 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, null, this.connected);

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

 if (this._reconnecting) {
 // connect() function is called while reconnect is in progress.
 // Terminate the auto reconnect process to use new connect options.
 this._reconnectTimeout.cancel();
 this._reconnectTimeout = null;
 this._reconnecting = false;
 }

 this.connectOptions = connectOptions;
 this._reconnectInterval = 1;
 this._reconnecting = false;
 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.onSuccess = function(grantedQos) { subscribeOptions.onSuccess({ invocationContext: subscribeOptions.invocationContext, grantedQos: grantedQos }); };
 }

 if (subscribeOptions.onFailure) {
 wireMessage.onFailure = function(errorCode) { subscribeOptions.onFailure({ invocationContext: subscribeOptions.invocationContext, errorCode: errorCode, errorMessage: format(errorCode) }); };
 }

 if (subscribeOptions.timeout) {
 wireMessage.timeOut = new Timeout(this, 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, 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);

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

 if (this.connected) {
 // Mark qos 1 & 2 message as "ACK required"
 // For qos 0 message, invoke onMessageDelivered callback if there is one.
 // Then schedule the 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);
 } else {
 // Currently disconnected, will not schedule this message
 // Check if reconnecting is in progress and disconnected publish is enabled.
 if (this._reconnecting && this.disconnectedPublishing) {
 // Check the limit which include the "required ACK" messages
 var messageCount = Object.keys(this._sentMessages).length + this._buffered_msg_queue.length;
 if (messageCount > this.disconnectedBufferSize) {
 throw new Error(format(ERROR.BUFFER_FULL, [this.disconnectedBufferSize]));
 } else {
 if (message.qos > 0) {
 // Mark this message as "ACK required"
 this._requires_ack(wireMessage);
 } else {
 wireMessage.sequence = ++this._sequence;
 this._buffered_msg_queue.push(wireMessage);
 }
 }
 } else {
 throw new Error(format(ERROR.INVALID_STATE, ["not connected"]));
 }
 }
 };

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

 if (this._reconnecting) {
 // disconnect() function is called while reconnect is in progress.
 // Terminate the auto reconnect process.
 this._reconnectTimeout.cancel();
 this._reconnectTimeout = null;
 this._reconnecting = false;
 }

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

 var 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 (var key in this._sentMessages)
 this._trace("_sentMessages ", key, this._sentMessages[key]);
 for (var 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._wsuri = wsurl;
 this.connected = false;

 ws.connect(wsurl, (err, value) => {
 if (!err) {
 this._trace("Connected successfully");
 } else {
 this._trace("Connection failed. Err:" + JSON.stringify(err));
 }
 });
 ws.on('open', (err, value) => {
 this._trace("on open, status:" + JSON.stringify(value));
 this._on_socket_open(value);
 });
 ws.on('message', (err, value) => {
 this._trace("on message, message:" + value);
 this._on_socket_message(value);
 });
 ws.on('close', (err, value) => {
 this._trace("on close, code is " + value.code + ", reason is " + value.reason);
 this._on_socket_close();
 });
 ws.on('error', (err) => {
 this._trace("on error, error:" + JSON.stringify(err));
 this._on_socket_error();
 });
 //ws.on('message',scope(this._on_socket_message, this));
 //ws.on('close',scope(this._on_socket_close, this));
 //ws.on('error',scope(this._on_socket_error, this));

 this.sendPinger = new Pinger(this, this.connectOptions.keepAliveInterval);
 this.receivePinger = new Pinger(this, this.connectOptions.keepAliveInterval);
 if (this._connectTimeout) {
 this._connectTimeout.cancel();
 this._connectTimeout = null;
 }
 this._connectTimeout = new Timeout(this, 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) {
 var 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 <= 0xF)
 hex = hex + "0" + messageBytes.toString(16);
 else
 hex = hex + messageBytes.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 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) {
 wireMessage.payloadMessage.duplicate = true;
 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(res) {
 // 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(data) {
 this._trace("Client._on_socket_message",data);
 var messages = this._deframeMessages(data);
 for (var i = 0; i < messages.length; i += 1) {
 this._handleMessage(messages);
 }
 };

 ClientImpl.prototype._deframeMessages = function(data) {
 var byteArray = new Uint8Array(data);
 var messages = [];
 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;
 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) {
 var errorStack = ((error.hasOwnProperty('stack') == 'undefined') ? error.stack.toString() : "No Error Stack Available");
 this._disconnected(ERROR.INTERNAL_ERROR.code, format(ERROR.INTERNAL_ERROR, [error.message, errorStack]));
 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 (this._reconnectTimeout)
 this._reconnectTimeout.cancel();

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

 for (var 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 = [];
 for (var msgId in this._sentMessages) {
 if (this._sentMessages.hasOwnProperty(msgId))
 sequencedMessages.push(this._sentMessages[msgId]);
 }

 // Also schedule qos 0 buffered messages if any
 if (this._buffered_msg_queue.length > 0) {
 var msg = null;
 var fifo = this._buffered_msg_queue.reverse();
 while ((msg = fifo.pop())) {
 sequencedMessages.push(msg);
 if (this.onMessageDelivered)
 this._notify_msg_sent[msg] = this.onMessageDelivered(msg.payloadMessage);
 }
 }

 // 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;
 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.
 // Will also now return if this connection was the result of an automatic
 // reconnect and which URI was successfully connected to.
 if (this.connectOptions.onSuccess) {
 this.connectOptions.onSuccess({ invocationContext: this.connectOptions.invocationContext });
 }

 var reconnected = false;
 if (this._reconnecting) {
 reconnected = true;
 this._reconnectInterval = 1;
 this._reconnecting = false;
 }

 // Execute the onConnected callback if there is one.
 this._connected(reconnected, this._wsuri);

 // 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.
 var 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();
 // This will need to be fixed when we add multiple topic support
 if (wireMessage.returnCode[0] === 0x80) {
 if (sentMessage.onFailure) {
 sentMessage.onFailure(wireMessage.returnCode);
 }
 } else if (sentMessage.onSuccess) {
 sentMessage.onSuccess(wireMessage.returnCode);
 }
 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) {
 var errorStack = ((error.hasOwnProperty('stack') == 'undefined') ? error.stack.toString() : "No Error Stack Available");
 this._disconnected(ERROR.INTERNAL_ERROR.code, format(ERROR.INTERNAL_ERROR, [error.message, errorStack]));
 return;
 }
 };

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

 /** @ignore */
 ClientImpl.prototype._on_socket_close = function() {
 if (!this._reconnecting) {
 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);

 ws.send(wireMessage.encode(), (err, value) => {
 if (!err) {
 this._trace("Message sent successfully");
 } else {
 this._trace("Failed to send the message. Err:" + JSON.stringify(err));
 }
 });
 /* 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 connected.
 * @param {reconnect} [boolean] indicate if this was a result of reconnect operation.
 * @param {uri} [string] fully qualified WebSocket URI of the server.
 */
 ClientImpl.prototype._connected = function(reconnect, uri) {
 // Execute the onConnected callback if there is one.
 if (this.onConnected)
 this.onConnected(reconnect, uri);
 };

 /**
 * Attempts to reconnect the client to the server.
 * For each reconnect attempt, will double the reconnect interval
 * up to 128 seconds.
 */
 ClientImpl.prototype._reconnect = function() {
 this._trace("Client._reconnect");
 if (!this.connected) {
 this._reconnecting = true;
 this.sendPinger.cancel();
 this.receivePinger.cancel();
 if (this._reconnectInterval < 128)
 this._reconnectInterval = this._reconnectInterval * 2;
 if (this.connectOptions.uris) {
 this.hostIndex = 0;
 this._doConnect(this.connectOptions.uris[0]);
 } else {
 this._doConnect(this.uri);
 }
 }
 };

 /**
 * 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);

 if (errorCode !== undefined && this._reconnecting) {
 //Continue automatic reconnect process
 this._reconnectTimeout = new Timeout(this, this._reconnectInterval, this._reconnect);
 return;
 }

 this.sendPinger.cancel();
 this.receivePinger.cancel();
 if (this._connectTimeout) {
 this._connectTimeout.cancel();
 this._connectTimeout = null;
 }

 // Clear message buffers.
 this._msg_queue = [];
 this._buffered_msg_queue = [];
 this._notify_msg_sent = {};

 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, reconnect: this.connectOptions.reconnect, uri: this._wsuri });
 }
 if (errorCode !== ERROR.OK.code && this.connectOptions.reconnect) {
 // Start automatic reconnect process for the very first time since last successful connect.
 this._reconnectInterval = 1;
 this._reconnect();
 return;
 }
 } else {
 // Otherwise we never had a connection, so indicate that the connect has failed.
 if (this.connectOptions.mqttVersion === 4 && this.connectOptions.mqttVersionExplicit === false) {
 this._trace("Failed to connect V4, dropping back to V3");
 this.connectOptions.mqttVersion = 3;
 if (this.connectOptions.uris) {
 this.hostIndex = 0;
 this._doConnect(this.connectOptions.uris[0]);
 } else {
 this._doConnect(this.uri);
 }
 } else if (this.connectOptions.onFailure) {
 this.connectOptions.onFailure({ invocationContext: this.connectOptions.invocationContext, errorCode: errorCode, errorMessage: errorText });
 }
 }
 }
 };

 /** @ignore */
 ClientImpl.prototype._trace = function() {
 // Pass trace message back to client's callback function
 if (this.traceFunction) {
 for (var i in arguments) {
 if (typeof arguments !== "undefined")
 arguments.splice(i, 1, JSON.stringify(arguments));
 }
 var record = Array.prototype.slice.call(arguments).join("");
 this.traceFunction({ severity: "Debug", message: record });
 }

 //buffer style trace
 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);
 else if (typeof arguments === "undefined") this._traceBuffer.push(arguments);
 else this._traceBuffer.push(" " + JSON.stringify(arguments));
 }
 }
 };

 /** @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 Paho.MQTT.Client} object.
 * 
 * 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.
 * 
 * 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.
 * 
 * In contrast there are some callback functions, most notably onMessageArrived,
 * that are defined on the {@link Paho.MQTT.Client} object.
 * These may get called multiple times, and aren't directly related to specific method invocations made by the client.
 *
 * @name Paho.MQTT.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 - read only the server's DNS hostname or dotted decimal IP address.
 * @property {number} port - read only the server's port.
 * @property {string} path - read only the server's path.
 * @property {string} clientId - read only 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 Paho.MQTT.Message} that was delivered.
 * </ol>
 * @property {function} onMessageArrived - called when a message has arrived in this Paho.MQTT.client.
 * Parameters passed to the onMessageArrived callback are:
 * <ol>
 * <li>{@link Paho.MQTT.Message} that has arrived.
 * </ol>
 * @property {function} onConnected - called when a connection is successfully made to the server.
 * after a connect() method.
 * Parameters passed to the onConnected callback are:
 * <ol>
 * <li>reconnect (boolean) - If true, the connection was the result of a reconnect.</li>
 * <li>URI (string) - The URI used to connect to the server.</li>
 * </ol>
 * @property {boolean} disconnectedPublishing - if set, will enable disconnected publishing in
 * in the event that the connection to the server is lost.
 * @property {number} disconnectedBufferSize - Used to set the maximum number of messages that the disconnected
 * buffer will hold before rejecting new messages. Default size: 5000 messages
 * @property {function} trace - called whenever trace is called. TODO
 */
 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 ipv6AddSBracket = (host.indexOf(":") !== -1 && host.slice(0, 1) !== "[" && host.slice(-1) !== "]");
 uri = "ws://" + (ipv6AddSBracket ? "[" + 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 > 65535)
 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._getOnConnected = function() { return client.onConnected; };
 this._setOnConnected = function(newOnConnected) {
 if (typeof newOnConnected === "function")
 client.onConnected = newOnConnected;
 else
 throw new Error(format(ERROR.INVALID_TYPE, [typeof newOnConnected, "onConnected"]));
 };

 this._getDisconnectedPublishing = function() { return client.disconnectedPublishing; };
 this._setDisconnectedPublishing = function(newDisconnectedPublishing) {
 client.disconnectedPublishing = newDisconnectedPublishing;
 };

 this._getDisconnectedBufferSize = function() { return client.disconnectedBufferSize; };
 this._setDisconnectedBufferSize = function(newDisconnectedBufferSize) {
 client.disconnectedBufferSize = newDisconnectedBufferSize;
 };

 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"]));
 };

 this._getTrace = function() { return client.traceFunction; };
 this._setTrace = function(trace) {
 if (typeof trace === "function") {
 client.traceFunction = trace;
 } else {
 throw new Error(format(ERROR.INVALID_TYPE, [typeof trace, "onTrace"]));
 }
 };

 /**
 * Connect this Messaging client to its server.
 *
 * @name Paho.MQTT.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 {Paho.MQTT.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>
 * @param {function} connectOptions.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>
 * @param {array} connectOptions.hosts - If present this contains either a set of hostnames or fully qualified
 * WebSocket URIs (ws://iot.eclipse.org:80/ws), 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.
 * @param {array} connectOptions.ports - If present the set of ports matching the hosts. If hosts contains URIs, this property
 * is not used.
 * @param {boolean} connectOptions.reconnect - Sets whether the client will automatically attempt to reconnect
 * to the server if the connection is lost.
 *<ul>
 *<li>If set to false, the client will not attempt to automatically reconnect to the server in the event that the
 * connection is lost.</li>
 *<li>If set to true, in the event that the connection is lost, the client will attempt to reconnect to the server.
 * It will initially wait 1 second before it attempts to reconnect, for every failed reconnect attempt, the delay
 * will double until it is at 2 minutes at which point the delay will stay at 2 minutes.</li>
 *</ul>
 * @param {number} connectOptions.mqttVersion - The version of MQTT to use to connect to the MQTT Broker.
 *<ul>
 *<li>3 - MQTT V3.1</li>
 *<li>4 - MQTT V3.1.1</li>
 *</ul>
 * @param {boolean} connectOptions.mqttVersionExplicit - If set to true, will force the connection to use the
 * selected MQTT Version or will fail to connect.
 * @param {array} connectOptions.uris - If present, should contain a list of fully qualified WebSocket uris
 * (e.g. ws://iot.eclipse.org:80/ws), that are tried in order in place of the host and port parameter of the construtor.
 * The uris are tried one at a time in order until one of them succeeds. Do not use this in conjunction with hosts as
 * the hosts array will be converted to uris and will overwrite this property.
 * @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",
 reconnect: "boolean",
 mqttVersion: "number",
 mqttVersionExplicit: "boolean",
 uris: "object"
 });

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

 if (connectOptions.mqttVersion > 4 || connectOptions.mqttVersion < 3) {
 throw new Error(format(ERROR.INVALID_ARGUMENT, [connectOptions.mqttVersion, "connectOptions.mqttVersion"]));
 }

 if (connectOptions.mqttVersion === undefined) {
 connectOptions.mqttVersionExplicit = false;
 connectOptions.mqttVersion = 4;
 } else {
 connectOptions.mqttVersionExplicit = true;
 }

 //Check that if password is set, so is username
 if (connectOptions.password !== undefined && connectOptions.userName === undefined)
 throw new Error(format(ERROR.INVALID_ARGUMENT, [connectOptions.password, "connectOptions.password"]));

 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 = null;

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

 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 Paho.MQTT.Client#subscribe
 * @function
 * @param {string} filter describing the destinations to receive messages from.
 * 
 * @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 Paho.MQTT.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 Paho.MQTT.Client#send
 * @function
 * @param {string|Paho.MQTT.Message} topic - mandatory The name of the destination to which the message is to be sent.
 * - If it is the only parameter, used as Paho.MQTT.Message object.
 * @param {String|ArrayBuffer} payload - The message data to be sent.
 * @param {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>
 * @param {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.
 * @throws {InvalidState} if the client is not connected.
 */
 this.send = function(topic, payload, qos, retained) {
 var message;

 if (arguments.length === 0) {
 throw new Error("Invalid argument." + "length");

 } else if (arguments.length == 1) {

 if (!(topic instanceof Message) && (typeof topic !== "string"))
 throw new Error("Invalid argument:" + typeof topic);

 message = topic;
 if (typeof message.destinationName === "undefined")
 throw new Error(format(ERROR.INVALID_ARGUMENT, [message.destinationName, "Message.destinationName"]));
 client.send(message);

 } else {
 //parameter checking in Message object
 message = new Message(payload);
 message.destinationName = topic;
 if (arguments.length >= 3)
 message.qos = qos;
 if (arguments.length >= 4)
 message.retained = retained;
 client.send(message);
 }
 };

 /**
 * Publish a message to the consumers of the destination in the Message.
 * Synonym for Paho.Mqtt.Client#send
 *
 * @name Paho.MQTT.Client#publish
 * @function
 * @param {string|Paho.MQTT.Message} topic - mandatory The name of the topic to which the message is to be published.
 * - If it is the only parameter, used as Paho.MQTT.Message object.
 * @param {String|ArrayBuffer} payload - The message data to be published.
 * @param {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>
 * @param {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.
 * @throws {InvalidState} if the client is not connected.
 */
 this.publish = function(topic, payload, qos, retained) {
 console.log("ublising message to: ", topic);
 var message;

 if (arguments.length === 0) {
 throw new Error("Invalid argument." + "length");

 } else if (arguments.length == 1) {

 if (!(topic instanceof Message) && (typeof topic !== "string"))
 throw new Error("Invalid argument:" + typeof topic);

 message = topic;
 if (typeof message.destinationName === "undefined")
 throw new Error(format(ERROR.INVALID_ARGUMENT, [message.destinationName, "Message.destinationName"]));
 client.send(message);

 } else {
 //parameter checking in Message object
 message = new Message(payload);
 message.destinationName = topic;
 if (arguments.length >= 3)
 message.qos = qos;
 if (arguments.length >= 4)
 message.retained = retained;
 client.send(message);
 }
 };

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

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

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

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

 this.isConnected = function() {
 return client.connected;
 };
 };

 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 onConnected() { return this._getOnConnected(); },
 set onConnected(newOnConnected) { this._setOnConnected(newOnConnected); },

 get disconnectedPublishing() { return this._getDisconnectedPublishing(); },
 set disconnectedPublishing(newDisconnectedPublishing) { this._setDisconnectedPublishing(newDisconnectedPublishing); },

 get disconnectedBufferSize() { return this._getDisconnectedBufferSize(); },
 set disconnectedBufferSize(newDisconnectedBufferSize) { this._setDisconnectedBufferSize(newDisconnectedBufferSize); },

 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); },

 get trace() { return this._getTrace(); },
 set trace(newTraceFunction) { this._setTrace(newTraceFunction); }

 };

 /**
 * An application message, sent or received.
 * 
 * All attributes may be null, which implies the default values.
 *
 * @name Paho.MQTT.Message
 * @constructor
 * @param {String|ArrayBuffer} payload The message data to be sent.
 * 
 * @property {string} payloadString read only The payload as a string if the payload consists of valid UTF-8 characters.
 * @property {ArrayBuffer} payloadBytes read only The payload as an ArrayBuffer.
 * 
 * @property {string} destinationName mandatory 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).
 * 
 * @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>
 * 
 * @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.
 * 
 * @property {Boolean} duplicate read only 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;
 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 topic() { return this._getDestinationName(); },
 set topic(newTopic) { this._setDestinationName(newTopic); },

 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
 };
})(ws);
return PahoMQTT;
};

const MQTT = LibraryFactory();
export default MQTT;
```
[/md]

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