如何向特定通道发送消息

const WebSocket = require('ws');
const wss = new WebSocket.Server({ port: 8080 });

wss.on('connection', function connection(ws) {
  ws.on('message', function incoming(message) {
    console.log('received: %s', message);
  });

  ws.send('Hello! Message From Server!!');
});

import paho.mqtt.client as mqtt

def on_connect(client, userdata, flags, rc):
    print("Connected with result code "+str(rc))
    client.subscribe("test/topic")

client = mqtt.Client()
client.on_connect = on_connect

client.connect("mqtt.eclipse.org", 1883, 60)
client.loop_start()

client.publish("test/topic", "Hello MQTT")

const http = require('http');

const server = http.createServer((req, res) => {
  if (req.url === '/message' && req.method === 'POST') {
    let body = '';
    req.on('data', chunk => {
      body += chunk.toString();
    });
    req.on('end', () => {
      res.end(`Received message: ${body}`);
    });
  } else {
    res.statusCode = 404;
    res.end();
  }
});

server.listen(3000, () => {
  console.log('Server running at http://localhost:3000/');
});