javascript - Troubles with offline messages using mqtt.js and Mosca -

i'm trying learn how send offline messages using mqtt.js , mosca based on author's demo , other instructions. below attempted, i'm not sure why listening client works online, not when subscription process includes offline configuration (qos, clientid, clean).

1.start standalone mosca broker using:

npm install mosca bunyan -g mosca -v | bunyan 

2.run following scripts (listed below) sequentially:

node subscribe.js   // user8 subscribes topic called channel-01 qos=1, closes connection node send.js        // txuser sends message on channel-01 node listen.js      // user8 reconnects , should see txuser's message 

3.attempt identify why listen.js not receive txuser's message.

here scripts:

subscribe.js user8 subscribes topic called channel-01 qos=1, closes connection.

var mqtt = require('mqtt');  var client = mqtt.connect({     servers: [{ host: 'localhost', port: 1883 }]     , clientid:"user8"     , clean:false });  client.subscribe('channel-01', {qos:1} , function(){   console.log("subscriber client: subscribed , closing connection.");   client.end(); }); 

send.js txuser sends message on channel-01

var mqtt = require('mqtt');  var client = mqtt.connect({   servers: [{ host: 'localhost', port: 1883 }]   , clientid:"txuser"   , clean:false });  client.on('connect', function(){   client.publish('channel-01', '* * * important msg ' + date() + ' * * *' , function() {     client.end( function (){       console.log('sender client: published message , closed connection');     });   }); }); 

listen.js user8 reconnects , should see txuser's message

var mqtt = require('mqtt');  var client = mqtt.connect({   servers: [{ host: 'localhost', port: 1883 }]   , clientid:"user8"   , clean:false });  client.subscribe('channel-01');  client.on('message', function(topic, message) {   // never fired when offline options (qos, clientid, clean)    // configured in subscribe.js    console.log('listener client: message received = ',message.tostring()); });  settimeout(function() {   console.log('listener client: exiting');   client.end(); },10*1000); 

package.js

{   "name": "mqtt-test-system",   "version": "0.0.1",   "dependencies": {     "mosca": "1.0.1",     "mqtt": "1.6.3"   } } 

ok figured out. apparently, needed add {qos:1} in publish statement within send.js script. should like:

client.publish('channel-01', '* * * important msg ' + date() + ' * * *' , {qos:1}, function() {...etc 

to clarify mqtt.js introduction/demo slides, submitted pr author , the updated slides here.