Uncaught InvalidStateError: Failed to execute 'send' on 'WebSocket': Still in CONNECTING state

When my page loads, I try to send a message to the server to initiate a connection, but it's not working. This script block is near the top of my file:

var connection = new WrapperWS();
connection.ident();
// var autoIdent = window.addEventListener('load', connection.ident(), false);

Most of the time, I see the error in the title:

Uncaught InvalidStateError: Failed to execute 'send' on 'WebSocket': Still in CONNECTING state

So I tried to catch the exception, as you can see below, but now it seems InvalidStateError is not defined and that produces a ReferenceError.

Here's the wrapper object for my websocket connection:

// Define WrapperWS

function WrapperWS() {
    if ("WebSocket" in window) {
        var ws = new WebSocket("ws://server:8000/");
        var self = this;

        ws.onopen = function () {
            console.log("Opening a connection...");
            window.identified = false;
        };
        ws.onclose = function (evt) {
            console.log("I'm sorry. Bye!");
        };
        ws.onmessage = function (evt) {
            // handle messages here
        };
        ws.onerror = function (evt) {
            console.log("ERR: " + evt.data);
        };

        this.write = function () {
            if (!window.identified) {
                connection.ident();
                console.debug("Wasn't identified earlier. It is now.");
            }
            ws.send(theText.value);
        };

        this.ident = function () {
            var session = "Test";
            try {
                ws.send(session);
            } catch (error) {
                if (error instanceof InvalidStateError) {
                    // possibly still 'CONNECTING'
                    if (ws.readyState !== 1) {
                        var waitSend = setInterval(ws.send(session), 1000);
                    }
                }
            }
        window.identified = true;
            theText.value = "Hello!";
            say.click();
            theText.disabled = false;
        };

    };

}

I am testing using Chromium on Ubuntu.

Solution 1:

You could send messages via a proxy function that waits for the readyState to be 1.

this.send = function (message, callback) {
    this.waitForConnection(function () {
        ws.send(message);
        if (typeof callback !== 'undefined') {
          callback();
        }
    }, 1000);
};

this.waitForConnection = function (callback, interval) {
    if (ws.readyState === 1) {
        callback();
    } else {
        var that = this;
        // optional: implement backoff for interval here
        setTimeout(function () {
            that.waitForConnection(callback, interval);
        }, interval);
    }
};

Then use this.send in place of ws.send, and put the code that should be run afterwards in a callback:

this.ident = function () {
    var session = "Test";
    this.send(session, function () {
        window.identified = true;
        theText.value = "Hello!";
        say.click();
        theText.disabled = false;
    });
};

For something more streamlined you could look into promises.

Solution 2:

This error is raised because you are sending your message before the WebSocket connection is established.

You can solve it by doing this simply:

conn.onopen = () => conn.send("Message");

This onopen function waits for your WebSocket connection to establish before sending your message.