feat: DBNMQTTool — DLD960 IoT MQTT 设备管理工具 (Python/tkinter 跨平台)

基于《DLD960_IoT_MQTT协议.md》V1.00 实现

功能：
- MQTT Broker 连接管理
- 设备自动发现（订阅 dld960/+/dev/# 通配符）
- 设备信息查询（dev_info_query）
- 网络配置（SSC/IoT TCP）+ Topic 配置
- 实时线圈数据监控（loop_data）+ 事件上报（event_report）
- 心跳监控（heartbeat）
- 控制命令：密码验证/设置、出厂初始化、设备复位

项目结构：
- main.py          主窗口 (tkinter GUI)
- dbn_mqtt_tool/
  - protocol.py    DLD960 IoT MQTT 协议定义
  - mqtt_client.py MQTT 客户端封装 (paho-mqtt)
  - device_manager.py 设备发现与状态管理

DBNMQTTool/dbn_mqtt_tool/mqtt_client.py

@@ -0,0 +1,141 @@
+"""
+MQTT 客户端封装
+"""
+
+import json
+import time
+import threading
+from typing import Callable, Optional
+from dataclasses import dataclass
+
+import paho.mqtt.client as mqtt
+
+from .protocol import parse_topic_dev_serial
+
+
+@dataclass
+class BrokerConfig:
+    host: str = "121.37.20.199"
+    port: int = 1883
+    username: str = ""
+    password: str = ""
+    client_id: str = ""
+    keepalive: int = 60
+
+
+class MqttClient:
+    """DLD960 IoT MQTT 客户端"""
+
+    def __init__(self):
+        self._client: Optional[mqtt.Client] = None
+        self._config = BrokerConfig()
+        self._connected = False
+        self._lock = threading.Lock()
+        self._message_callbacks: list[Callable[[str, str, dict], None]] = []
+        self._status_callbacks: list[Callable[[bool, str], None]] = []
+
+    @property
+    def connected(self) -> bool:
+        return self._connected
+
+    def on_status_change(self, callback: Callable[[bool, str], None]):
+        self._status_callbacks.append(callback)
+
+    def on_message(self, callback: Callable[[str, str, dict], None]):
+        """回调参数: (topic, dev_serial, payload_dict)"""
+        self._message_callbacks.append(callback)
+
+    def _notify_status(self, connected: bool, msg: str):
+        for cb in self._status_callbacks:
+            try:
+                cb(connected, msg)
+            except Exception:
+                pass
+
+    def _notify_message(self, topic: str, payload: dict):
+        dev_serial = parse_topic_dev_serial(topic) or ""
+        for cb in self._message_callbacks:
+            try:
+                cb(topic, dev_serial, payload)
+            except Exception:
+                pass
+
+    # ---- MQTT callbacks ----
+
+    def _on_connect(self, client, userdata, flags, reason_code, properties=None):
+        rc = reason_code if isinstance(reason_code, int) else reason_code.value
+        if rc == 0:
+            self._connected = True
+            self._notify_status(True, "已连接到 Broker")
+
+            # 订阅所有设备的上报 topic
+            from .protocol import (
+                TOPIC_ALL_CONFIG_RESP, TOPIC_ALL_DATA_LOOP,
+                TOPIC_ALL_DATA_EVENT, TOPIC_ALL_STATUS
+            )
+            client.subscribe(TOPIC_ALL_CONFIG_RESP, qos=1)
+            client.subscribe(TOPIC_ALL_DATA_LOOP, qos=1)
+            client.subscribe(TOPIC_ALL_DATA_EVENT, qos=1)
+            client.subscribe(TOPIC_ALL_STATUS, qos=0)
+        else:
+            self._connected = False
+            self._notify_status(False, f"连接失败 (rc={rc})")
+
+    def _on_disconnect(self, client, userdata, flags, reason_code, properties=None):
+        self._connected = False
+        self._notify_status(False, "已断开连接")
+
+    def _on_message(self, client, userdata, msg: mqtt.MQTTMessage):
+        try:
+            payload = json.loads(msg.payload.decode("utf-8"))
+        except (json.JSONDecodeError, UnicodeDecodeError):
+            payload = {"_raw": msg.payload.hex()}
+        self._notify_message(msg.topic, payload)
+
+    # ---- Public API ----
+
+    def connect(self, config: Optional[BrokerConfig] = None):
+        if config:
+            self._config = config
+
+        if self._client:
+            self.disconnect()
+
+        client_id = self._config.client_id or f"dbn_mqtt_tool_{int(time.time())}"
+
+        # MQTT 5.0 用 CallbackAPIVersion.VERSION2
+        self._client = mqtt.Client(
+            client_id=client_id,
+            protocol=mqtt.MQTTv311,
+        )
+        if self._config.username:
+            self._client.username_pw_set(self._config.username, self._config.password)
+
+        self._client.on_connect = self._on_connect
+        self._client.on_disconnect = self._on_disconnect
+        self._client.on_message = self._on_message
+
+        self._client.connect_async(self._config.host, self._config.port, self._config.keepalive)
+        self._client.loop_start()
+
+    def disconnect(self):
+        if self._client:
+            self._client.loop_stop()
+            self._client.disconnect()
+            self._client = None
+        self._connected = False
+
+    def publish(self, topic: str, payload: dict, qos: int = 1):
+        """发送 JSON 消息到指定 topic"""
+        if not self._client or not self._connected:
+            raise ConnectionError("MQTT 未连接")
+        data = json.dumps(payload, ensure_ascii=False)
+        self._client.publish(topic, data, qos=qos)
+
+    def send_command(self, dev_serial: str, cmd: str, data: Optional[dict] = None, qos: int = 1) -> int:
+        """向设备发送命令，返回 msg_id"""
+        from .protocol import build_request, get_topic_for_cmd
+        msg = build_request(cmd, data)
+        topic = get_topic_for_cmd(cmd, dev_serial)
+        self.publish(topic, msg, qos=qos)
+        return msg["msg_id"]