169 lines
6.6 KiB
JavaScript
169 lines
6.6 KiB
JavaScript
/**
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* MqttClient —— 浏览器/小程序 MQTT over WebSocket 重连封装
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*
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* 稳定性策略（对应路线 B2「即时通信稳定性」）：
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* 1. 指数退避重连：基数 1s，上限 30s，成功一次后重置。
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* 2. 会话恢复：clean=false 时重连自动补投离线消息（由 Broker 保证）。
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* 3. 遗嘱（LWT）：连接异常断开时 Broker 代发 will，上层可据此标记「离线」。
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* 4. 心跳兜底：onclose 即触发重连，不依赖 broker 的 keepalive 超时。
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*
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* 用法：
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* const c = new MqttClient('wss://your.host/mqtt', {
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* clientId: 'web-' + uid, username, password, clean: false,
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* will: { topic: 'presence/' + uid, payload: 'offline', qos: 1, retain: true }
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* });
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* c.on('connect', () => c.subscribe('topic/a'));
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* c.on('message', (t, p) => console.log(t, p));
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*/
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(function (global) {
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'use strict';
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const BACKOFF_BASE = 1000; // 1s
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const BACKOFF_MAX = 30000; // 30s
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const BACKOFF_FACTOR = 1.8;
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function MqttClient(url, opts) {
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this.url = url;
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this.opts = opts || {};
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this.clientId = this.opts.clientId || ('mqttjs_' + Math.random().toString(16).slice(2, 10));
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this._listeners = {};
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this._ws = null;
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this._connected = false;
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this._closedByUser = false;
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this._backoff = BACKOFF_BASE;
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this._retryTimer = null;
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this._subscriptions = {}; // topic -> qos，重连后自动重订
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}
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MqttClient.prototype.on = function (evt, fn) {
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(this._listeners[evt] = this._listeners[evt] || []).push(fn);
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return this;
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};
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MqttClient.prototype._emit = function (evt, a, b) {
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(this._listeners[evt] || []).forEach((fn) => fn(a, b));
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};
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MqttClient.prototype.connect = function () {
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this._closedByUser = false;
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this._open();
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return this;
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};
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MqttClient.prototype._open = function () {
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let ws;
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try {
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ws = new WebSocket(this.url, ['mqtt']);
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} catch (e) {
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return this._scheduleReconnect();
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}
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this._ws = ws;
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ws.binaryType = 'arraybuffer';
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ws.onopen = () => {
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// 发送 MQTT CONNECT（极简 CONNECT 报文，支持 will）
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const buf = this._buildConnect();
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ws.send(buf);
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};
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ws.onmessage = (ev) => {
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const pkt = this._parseConnAck(ev.data);
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if (pkt && pkt.sessionPresent) {
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this._emit('resume'); // 会话恢复，Broker 会在后台补投离线消息
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}
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this._connected = true;
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this._backoff = BACKOFF_BASE;
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this._emit('connect');
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Object.keys(this._subscriptions).forEach((t) => this.subscribe(t, this._subscriptions[t]));
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};
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ws.onclose = () => {
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if (this._connected) this._emit('disconnect');
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this._connected = false;
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if (!this._closedByUser) this._scheduleReconnect();
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};
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ws.onerror = () => { try { ws.close(); } catch (e) {} };
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};
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MqttClient.prototype._scheduleReconnect = function () {
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if (this._closedByUser) return;
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this._emit('reconnecting', this._backoff);
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clearTimeout(this._retryTimer);
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this._retryTimer = setTimeout(() => {
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this._backoff = Math.min(BACKOFF_MAX, Math.floor(this._backoff * BACKOFF_FACTOR));
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this._open();
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}, this._backoff);
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};
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MqttClient.prototype.subscribe = function (topic, qos) {
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this._subscriptions[topic] = qos || 0;
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if (!this._connected || !this._ws) return;
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this._ws.send(this._buildSubscribe(topic, qos || 0));
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};
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MqttClient.prototype.publish = function (topic, payload, qos, retain) {
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if (!this._connected || !this._ws) return false;
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this._ws.send(this._buildPublish(topic, payload, qos || 0, retain ? 1 : 0));
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return true;
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};
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MqttClient.prototype.end = function () {
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this._closedByUser = true;
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clearTimeout(this._retryTimer);
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if (this._ws) { try { this._ws.close(); } catch (e) {} }
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};
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/* ---------- 以下为最小 MQTT 报文构造（仅覆盖 CONNECT/SUBSCRIBE/PUBLISH） ---------- */
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MqttClient.prototype._encStr = function (s) {
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const b = new TextEncoder().encode(s);
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return new Uint8Array([b.length >> 8, b.length & 0xff, ...b]);
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};
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MqttClient.prototype._buildConnect = function () {
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const o = this.opts;
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const cid = this._encStr(this.clientId);
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let payload = cid;
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if (o.username) payload = this._join(payload, this._encStr(o.username), this._encStr(o.password || ''));
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if (o.will) {
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payload = this._join(payload, this._encStr(o.will.topic), this._encStr(o.will.payload || ''));
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}
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let varHdr = new Uint8Array([4, 0x02 /*clean*/, 0x3c /*keepalive 60*/]);
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if (o.clean === false) varHdr[1] = 0;
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let flags = 0;
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if (o.username) flags |= 0x80;
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if (o.password) flags |= 0x40;
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if (o.will) flags |= 0x04 | ((o.will.qos || 0) << 3) | ((o.will.retain ? 1 : 0) << 5);
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varHdr[1] |= flags;
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const body = this._join(varHdr, payload);
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return this._wrap(1, body);
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};
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MqttClient.prototype._buildSubscribe = function (topic, qos) {
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const pid = new Uint8Array([0x00, 0x01]);
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const t = this._join(this._encStr(topic), new Uint8Array([qos]));
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return this._wrap(8, this._join(pid, t));
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};
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MqttClient.prototype._buildPublish = function (topic, payload, qos, retain) {
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const t = this._encStr(topic);
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const p = typeof payload === 'string' ? new TextEncoder().encode(payload) : new Uint8Array(payload);
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return this._wrap(3 | (qos << 1) | (retain << 0), this._join(t, p));
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};
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MqttClient.prototype._wrap = function (cmd, body) {
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const len = body.length;
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const rem = [len & 0x7f];
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if (len > 127) rem.unshift((len >> 7) & 0x7f | 0x80);
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return new Uint8Array([cmd << 4, ...rem, ...body]);
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};
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MqttClient.prototype._join = function (...arrs) {
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let n = 0; arrs.forEach((a) => n += a.length);
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const out = new Uint8Array(n);
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let p = 0; arrs.forEach((a) => { out.set(a, p); p += a.length; });
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return out;
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};
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MqttClient.prototype._parseConnAck = function (data) {
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try {
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const buf = new Uint8Array(data);
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return { sessionPresent: (buf[2] & 0x01) === 1, code: buf[3] };
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} catch (e) { return null; }
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};
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global.MqttClient = MqttClient;
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if (typeof module !== 'undefined') module.exports = MqttClient;
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})(typeof window !== 'undefined' ? window : this);
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