socket io creating multiple connection on reload

I am trying to make a socket io push logs to client UI.
Here is the code in angular 2

ngAfterViewInit()
this.socket=io('http://localhost:9999')
this.socket.on('send-log-data-'+this.labName,function(data)
this.loaddata(data)
.bind(this))

@HostListener('window:beforeunload', ['$event'])
doSomething($event)
// if(this.hasChanges) $event.returnValue='Your data will be lost!';
this.socket.emit('disconnect',"")

}


After looking in to server side i can see on every reload of web page two new connection are getting created and one connection is getting closed.

On First Reload

new connection made
new connection made
Reloading
Reloading
disonnect request came.Disconnecting


On second reload

Reloading
new connection made
new connection made
new connection made
new connection made
Reloading
Reloading
disonnect request came.Disconnecting
disonnect request came.Disconnecting


Server side code as asked is

var Tail=require('tail').Tail
module.exports =

io_connect_disconnect : (labName,io) =>

io.on('connection',function(socket)
console.log("new connection made")
filename="output.log"
var options= fromBeginning: true
tail = new Tail(filename,options)

console.log("new connection made")
tail.on("line", function(data)
console.log("triggering")
console.log(data)
io.sockets.emit('send-log-data-'+labName,data)
)
socket.on('disconnect',function()
tail.unwatch()
console.log("disonnect request came.Disconnecting")
socket.disconnect();
)
)




Can anyone help me with this strange situation ?

1 Answer
1

The problem is that you are registering a new event handler every time the page is reloaded. This causes the data to be sent multiple times. I had the same issue and I solved by using io.once() instead of io.on() in the server.

io.once()

io.on()

io.once('connection',function(socket)
console.log("new connection made")
...



This causes the connection listener to be unregistered as soon as it is called, and the data is sent only once.

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