MQTT 消息在 React 中的 Websockets 上打开太多 TCP 连接

Question

我有一个 ESP32 设备使用 umqtt 模块以非常快的速度发送数据。此外，Mosquitto 代理在端口 1883 上侦听 mqtt，在端口 9001 上侦听 websockets。最后，一个实时显示消息的 React App。

问题是每次React App收到来自ESP设备的消息时，都会建立一个新的TCP连接，导致打开了很多连接，如下所示：

pi@rthree:/etc/mosquitto $ ss -s
Total: 449
TCP:   334 (estab 257, closed 70, orphaned 0, timewait 68)

Transport Total     IP        IPv6
RAW   1         0         1        
UDP   6         3         3        
TCP   264       261       3        
INET      271       264       7        
FRAG      0         0         0

如何解决连接过载问题？

有什么建议吗？

在前端，这是React App：

import {useEffect,useState} from 'react'
import './App.css';
import mqtt from "mqtt";

function App() {
const [mess, setMess] = useState("0")

const options = {"username":"user","password":"password"}
const client = mqtt.connect("ws://192.168.1.166:9001",options);
client.subscribe("temp_orientation");

const update_mqtt = () =>{
    client.on("message", function (topic, message) {
      const mssg = message.toString();
      setMess(mssg);
         
    } )
}
useEffect(()=>{
    update_mqtt();
},[])

  return (
    <div className="App">
      <header className="App-header">

      <h1>Data: {mess}</h1>
      </header>
    </div>
  );
}

export default App;

这是后端：

import mpu6050
from machine import SoftI2C, Pin, PWM, ADC, reset
from time import sleep
import network
import wifi
import math

from umqtt import robust as mqtt

try:
    wifi.wifi_connect()
except:
    wifi.hotspot_connect()

mqtt_server = "192.168.1.166"
client_id = "usero"
topic_sub = 'temp_orientation'

def sub_cb(topic, msg):
  print(topic, msg)


def connect_and_subscribe():
  global client_id, mqtt_server, topic_sub
  client = mqtt.MQTTClient(client_id, mqtt_server,user='user00001', password='password')
  client.set_callback(sub_cb)
  client.connect()
  client.subscribe(topic_sub)
  return client

def restart_and_reconnect():
  print('Failed to connect to MQTT broker. Reconnecting...')
  sleep(1)
  reset()

try:
  client = connect_and_subscribe()
except OSError as e:
  restart_and_reconnect()

# mpu sensor

i2c = SoftI2C(scl=Pin(22),sda=Pin(21))
a = mpu6050.accel(i2c)

tprev = 0
mprev = False
m = 0

while True:
    
    values = a.get_values()
    z = values["AcZ"]
    t = math.floor(int(values["Tmp"]) * 10) / 10
    
    if int(z) < 0:
        m = "DOWN"
        
    if int(z) > 0:
        m = "UP"
     
    if t != tprev or m != mprev:
        mprev = m
        tprev = t
        try:
            client.check_msg()
            client.publish("temp_orientation", "{} {}".format(str(t),m))
        
        except OSError as e:
            restart_and_reconnect()
                      
    sleep(0.2)

谢谢。

Answer 1

将所有mqtt逻辑常量移入useEffect后解决。现在它会在收到每条消息后更新状态，并且不会保持连接打开。

import {useEffect,useState} from 'react'
import './App.css';
import mqtt from "mqtt";

function App() {
const [mess, setMess] = useState("0")

useEffect(()=>{
    const options = {"username":"user","password":"password"}
    const client = mqtt.connect("ws://192.168.1.166:9001",options);
    client.subscribe("temp_orientation");
    const update_mqtt = () =>{
        client.on("message", function (topic, message) {
            const mssg = message.toString();
            setMess(mssg);
         } )
}
    update_mqtt();
},[])

  return (
    <div className="App">
      <header className="App-header">

      <h1>Data: {mess}</h1>
      </header>
    </div>
  );
}

export default App;

MQTT 消息在 React 中的 Websockets 上打开太多 TCP 连接

MQTT messages opening too many TCP connections on Websockets in React

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