如何使用node.js和socket.io检查Azure IOT Hub发送方是否已停止

Question

I have two programs, a sender and a receiver. The sender sends some message to device on IOT Hub and receiver in turn receives those messages as long as sender sends them. I am using socket.io to broadcast those messages to connected clients. However when the sender is stopped, the receiver also stops but the last message sent by sender is going to broadcasted infinitely until i close the receiver or the sender starts again and sends new messages. The last message will get duplicated and broadcasted infinitely. How to check if the sender program has stopped?

this is the sender prrogram:

var clientFromConnectionString = require('azure-iot-device-mqtt').clientFromConnectionString;
var Message = require('azure-iot-device').Message;
var connectionString = 'conn_string'
var client = clientFromConnectionString(connectionString);

var avgTemperature = 20;

var printResult = function (err, res) {
    if (err) {
        console.log('send error: ' + err.toString());
        return;
    }
    console.log('send status: ' + res.constructor.name);
};

setInterval(function () {
    var currentTemperature = avgTemperature + (Math.random() * 10) - 2;
    var data = JSON.stringify({
        deviceId: 'test',
        temperature: currentTemperature,
        latitude: 50.286264,
        longitude: 19.104079,
        time: Date.now()
    });
    var message = new Message(data);
    console.log("Sending message: " + message.getData());
    client.sendEvent(message, printResult);
}, 5000);

this is the receiver and the socket.io which broadcasts to the client:

var app = require('express')();
var http = require('http').Server(app);
var io = require('socket.io')(http);
var EventHubClient = require('azure-event-hubs').Client;
var connectionString = 'conn_string'

var printError = function (err) {
    console.log(err.message);
};

var result;

var printMessage = function (message) {
    console.log('Message received: ');
    result = JSON.stringify(message.body);
    console.log('message: ' + result);
    /* io.on('connection', function(socket){


     socket.on('chat message', function(msg){

     io.emit('chat message', result);
  }); 
}); */

        console.log('');
};

count =0;

app.get('/', function(req, res){
  res.sendFile(__dirname + '/index.html');
});

io.on('connection', function(socket){
  console.log('user connected');
  socket.on('chat message', function(msg){

     io.emit('chat message', result);

  }); 
  socket.on('disconnect', function(){
    console.log('user disconnected');
      socket.removeAllListeners('disconnect');
      io.removeAllListeners('connection');
  });
});

var client = EventHubClient.fromConnectionString(connectionString);
client.open()
    .then(client.getPartitionIds.bind(client))
    .then(function (partitionIds) {
        return partitionIds.map(function (partitionId) {
            return client.createReceiver('$Default', partitionId, { 'startAfterTime' : Date.now()}).then(function(receiver) {
                console.log('Created partition receiver: ' + partitionId)
                receiver.on('errorReceived', printError);
                receiver.on('message', printMessage);
            });
        });
    })
    .catch(printError);


http.listen(3000, function(){
  console.log('listening on *:3000');
});

Answer 1

According to your code. Whenever the sender stops sending, the receiver will not receive the messages and will wait for the sender to send new messages. However, if you still want to check, you can use sequence numbers with sender messages or associate Id with them to check duplicates.