Your connection callback (`function(socket) { … }`) needs a reference to the external `this` (the View instance) to access `sender`.
Instead of declaring `self` to forward its reference inside the callback, I'd advise keeping `this.sender` inside, and binding the callback to the external `this`:

    this.wss.on('connection', function(socket) {
        this.sender.on('send', function(data) {
            socket.send(JSON.stringify(data));
        });
    }.bind(this));

That pattern allows for keeping `this` references consistent across callbacks.