Ubuntu Mosquitto broker websocket is not working - websocket

Question

I'm new at IoT & MQTT communication protocol. I'm trying to connect my broker which runs at Amazon Ec2 from my Vue web app via Websockets. I have started mosquitto with:
root#ip-xxx-xx-xx-xx:~# mosquitto -c /etc/mosquitto/conf.d/default.conf
1618518468: mosquitto version 1.6.7 starting
1618518468: Config loaded from /etc/mosquitto/conf.d/default.conf.
1618518468: Opening ipv4 listen socket on port 1883.
1618518468: Opening ipv6 listen socket on port 1883.
1618518468: Opening websockets listen socket on port 9001.
/etc/mosquitto/conf.d/default.conf file contains:
listener 1883
protocol mqtt
allow_anonymous true
listener 9001
protocol websockets
allow_anonymous true
My test js file is:
var mqtt = require('mqtt');
var count =0;
var client = mqtt.connect("mqtt://xx.xxx.xxx.xxx",{clientId:"mqttjs01"});
console.log("connected flag " + client.connected);
//handle incoming messages
client.on('message',function(topic, message, packet){
console.log("message is "+ message);
console.log("topic is "+ topic);
});
client.on("connect",function(){
console.log("connected "+ client.connected);
})
//handle errors
client.on("error",function(error){
console.log("Can't connect" + error);
process.exit(1)});
//publish
function publish(topic,msg,options){
console.log("publishing",msg);
if (client.connected == true){
client.publish(topic,msg,options);
}
count+=1;
if (count==2) //ens script
clearTimeout(timer_id); //stop timer
client.end();
}
//////////////
var options={
retain:true,
qos:1};
var topic="acs";
var message="test message";
var topic_list=["topic2","topic3","topic4"];
var topic_o={"topic22":0,"topic33":1,"topic44":1};
console.log("subscribing to topics");
client.subscribe(topic,{qos:0}); //single topic
client.subscribe(topic_list,{qos:1}); //topic list
client.subscribe(topic_o); //object
var timer_id=setInterval(function(){publish(topic,message,options);},5000);
//notice this is printed even before we connect
console.log("end of script");
But I'm getting this error:
New client connected from 176.xxx.xxx.xx as mqttjs01 (p2, c1, k60).
1618518546: Socket error on client mqttjs01, disconnecting.
I have installed libwebsockets, I have tried with various mosquitto versions. Current version is: 1.6.7.
Is there any problem with my client or broker? How can I fix this?

Answer 1

At the end of the publish() function the if statement is missing enclosing braces so it doesn't do what you think it does.
function publish(topic,msg,options){
console.log("publishing",msg);
if (client.connected == true){
client.publish(topic,msg,options);
}
count+=1;
if (count==2) //ens script
clearTimeout(timer_id); //stop timer
client.end();
}
Lets fix the indentation so we can see more clearly.
function publish(topic,msg,options){
console.log("publishing",msg);
if (client.connected == true){
client.publish(topic,msg,options);
}
count+=1;
if (count==2) //ens script
clearTimeout(timer_id); //stop timer
client.end();
}
As you can see client.end() will ALWAYS be called when ever publish() is called. If you only want to publish twice you need to wrap the 2 statements in the braces (this is not python where whitespace has meaning)
if (count==2) { //ens script
clearTimeout(timer_id); //stop timer
client.end();
}
You really should indent all your code properly it will make it much easier to read and to spot errors like this.
Also as #JDAllen mentioned you are not making use of the WebSocket connection, unless this code is running in the browser, where the sandbox will force it to be a WebSocket connection even if you specify mqtt:// as the schema in the URL, and you will have to include the port number to make it actually connect. e.g.
ws://xxx.xxx.xxx.xxx:9001