无法将Raspberry Pi Pico W连接到MQTT代理，未收到CONNACK响应

问题描述 #

我尝试将Raspberry Pi Pico W连接到运行MQTT代理和Node-RED服务器的虚拟机，该MQTT代理受密码保护。Node-RED的MQTT节点已配置代理IP且连接正常，但通过Thonny在Pico上运行MicroPython脚本时，设备无法连接到MQTT代理，收不到CONNACK信号，报错socket read timeout。

运行的MicroPython脚本 #

from mqtt_as import MQTTClient, config
import uasyncio as asyncio
import socket

# Local configuration
config['ssid'] = 'user'
config['wifi_pw'] = 'password'
config['server'] = '192.168.122.1'  # Change to suit e.g. 'iot.eclipse.org'

async def messages(client):  # Respond to incoming messages
    async for topic, msg, retained in client.queue:
        print((topic, msg, retained))

async def up(client):  # Respond to connectivity being (re)established
    while True:
        await client.up.wait()  # Wait on an Event
        client.up.clear()
        await client.subscribe('Nodered', 0)  # renew subscriptions

async def main(client):
    print("Hello")
    await client.connect()
    print("Hello")
    for coroutine in (up, messages):
        asyncio.create_task(coroutine(client))
    n = 0
    while True:
        await asyncio.sleep(5)
        print('publish', n)
        # If WiFi is down the following will pause for the duration.
        await client.publish('Nodered', 'hello there', qos = 0)
        n += 1

config["queue_len"] = 1  # Use event interface with default queue size
MQTTClient.DEBUG = True  # Optional: print diagnostic messages
client = MQTTClient(config)
try:
    asyncio.run(main(client))
finally:
    client.close()  # Prevent LmacRxBlk:1 errors

错误信息 #

MPY: soft reboot
Hello
Checking WiFi integrity.
Got reliable connection
Connecting to broker.
Traceback (most recent call last):
  File "<stdin>", line 38, in <module>
  File "uasyncio/core.py", line 1, in run
  File "uasyncio/core.py", line 1, in run_until_complete
  File "uasyncio/core.py", line 1, in run_until_complete
  File "<stdin>", line 22, in main
  File "/lib/mqtt_as.py", line 645, in connect
  File "/lib/mqtt_as.py", line 314, in _connect
  File "/lib/mqtt_as.py", line 213, in _as_read
OSError: (-1, 'Timeout on socket read')

解决方案 #

1. 添加MQTT认证信息 #

你的MQTT代理是密码保护的，但当前脚本未配置用户名和密码，这是最可能的原因。在config配置中添加以下两行：

config['user'] = '你的MQTT代理用户名'
config['password'] = '你的MQTT代理密码'

2. 验证网络连通性 #

• 测试端口可达性：在Pico上添加一段代码测试MQTT默认端口（1883）是否开放：

  s = socket.socket()
  try:
      s.connect(('192.168.122.1', 1883))
      print("端口1883可连接")
  except OSError as e:
      print(f"连接失败: {e}")
  s.close()
  

• 检查防火墙设置：确保虚拟机的防火墙允许1883端口的入站连接，可临时关闭防火墙测试。
• 确认代理绑定地址：检查MQTT代理的配置文件，确保bind_address设置为0.0.0.0（允许所有IP访问），而非127.0.0.1（仅本地访问）。

3. 调整连接超时时间 #

如果网络存在延迟，可增大mqtt_as的连接超时，在config中添加：

config['connect_timeout'] = 10  # 单位：秒，默认可能为5秒

4. 查看MQTT代理日志 #

检查虚拟机上MQTT代理的日志文件，查看是否有来自Pico的连接请求记录，比如认证失败、IP被拒绝等信息，这能快速定位问题。

内容的提问来源于stack exchange，提问作者Magnus Bane