Websocket return from function

Question

im trying to use websockets for my application

function Connector()
{
  this.protocol = "bla";
  this.socket   = new WebSocket("ws://echo.websocket.org", this.protocol);
}

Connector.prototype.emit = function()
{
  this.socket.send('abc');
}

For me it is possible to call:

var con = new Connector();
con.emit();

from my Browsers console but from source code i get the following error message

InvalidStateError: An attempt was made to use an object that is not, or is no longer, usable

what is the problem ?

fedeghe · Accepted Answer · 2016-01-29T16:15:15.853

Shouldn 't You wait for the right value of readyState ?

function Connector(wsurl) {
    this.protocol = "bla";
    this.socket = new WebSocket(wsurl, this.protocol);
}
Connector.prototype.emit = function(msg) {

    var self = this;

    (function _waitForSocketConnection(callback) {
        setTimeout(function() {
            if (self.socket.readyState === 1) {
                console.log("Connection is made")
                if (callback != null) {
                    callback();
                }
                return;

            } else {
                console.log("wait for connection...")
                _waitForSocketConnection(callback);
            }
        }, 5);
    })(function() {
        console.log("message sent!!!");
        self.socket.send(msg);
    });
}


var con = new Connector("ws://echo.websocket.org");
con.emit('abc');
//or even worst
new Connector("ws://echo.websocket.org").emit('def');

http://stackoverflow.com/questions/13546424/how-to-wait-for-a-websockets-readystate-to-change — fedeghe, Jan 29 '16 at 11:02
yeah.. `console.log("message sent!!!");` is not exactly in the right place anyway ... :) — fedeghe, Feb 01 '16 at 15:22

Oxi · Answer 2 · 2016-01-29T16:37:21.620

Are you waiting for the .onopen function to be called ? you are supposed to send message on a websocket only after the connection is established. you can try something like

    function Connector() {
        this.protocol = "bla";
        this.socket   = new WebSocket("ws://echo.websocket.org", this.protocol);
        this.connected = false;
    }
    Connector.prototype.emit = function() {

        if(this.connected) {
            try {
                this.socket.send('abc');
                return true;
            }
            catch(err) {
                console.log('Error' + err.message);
                return false;
            }       
        }
        else {
            console.log('CRITICAL Error No WS');
            return false;
        }
    }

    con.socket.onopen = function() {
        console.log("webSocket Connected");
        con.connected = true;
        //send message here
        con.emit();
    };
    con.socket.onclose = function(e) {
        //closed
        con.connected = false;
    };
    con.socket.onerror = function(e) {
        console.log("Error",e);
    };
    con.socket.onmessage = function(msg) {
        //msg
    }

UPDATED CODE

function Connector(protocol, cB){
    var self = this,
        this.protocol = protocol,
        this.socket   = new WebSocket("ws://echo.websocket.org", this.protocol),
        this.connected = false;    

    this.socket.onopen = function() {
        self.connected = true;
        cB();
    };

    this.socket.onclose = function(e) {
        self.connected = false;
        //closed, inform(event)
    };

    this.socket.onerror = function(e) {
        //error, inform(event)
    };

    this.socket.onmessage = function(msg) {
        //msg, inform(event)
    }
}

Connector.prototype.emit = function(msg) {
    if(this.connected) {
        try {
            this.socket.send(msg);
            return true;
        }
        catch(err) {
            console.log('Error' + err.message);
            return false;
        }       
    }
    else {
        console.log('CRITICAL Error No WS');
        return false;
    }
}

var con = new Connector('blah',function() {
    con.emit('abc');
});

and the simplest case with out a constructor or any other events; Just simple/basic ws client

var socket   = new WebSocket("ws://echo.websocket.org", 'bla');
socket.onopen = function() {
    socket.send('msg');
};

much better for the problems at the "beginning", but what if he calls emit() after the connection died? — Gavriel, Jan 29 '16 at 10:54
@Gavriel : i tried to in-corporate that quickly... thanks for the tip :) — Oxi, Jan 29 '16 at 11:02
@Oxi doesn't is seems a really bad idea to set onXXX methods from the instance???... you should write em for every instance...repeating even all the setting on _connected_ that should be definitely be private.... not only, you should write em AFTER creating a instance!!!... — fedeghe, Jan 29 '16 at 14:37
@Oxi ...ohhh dude.... thanks for the down vote... instead of having a constructive discussion... you just ran away with a click.I bet it`s not the first time You miss the chance to learn something... Good luck!!! — fedeghe, Jan 29 '16 at 16:02
@fedeghe : I have updated my answer. added two more code sample — Oxi, Jan 29 '16 at 16:39
@fedeghe : corrected the down vote mistake :) . Thanks, it was good one — Oxi, Jan 29 '16 at 16:40

Voreny · Answer 3 · 2016-01-29T10:57:41.090

1

You should wait for the socket to connect first. The Websocket constructor is non-blocking, which means that when you create a new Websocket, it connects in the background and your code continues. You need to set a onopen attribute on your Websocket to a callback that will get executed when the Websocket connects.

Here you can see how it's done what events you can listen for.

edited Jan 29 '16 at 10:57

answered Jan 29 '16 at 10:54

Voreny

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Websocket return from function

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