使用套接字。io和节点。js、表达和玉石

I have some trouble to use Socket.io even just to test if a client is connected. I've tried many things and I think that my mistake is, maybe, when I do the app.get function. I have also tried to do this in an route js file but it wasn't conclusive neither. So here are my different codes : I have some trouble to use Socket.io even just