What does io.connect('http://localhost:4000) mean?

Question

I am building an application using react.js and socket.io, I have my backend code for the socket.io server in one folder and the client/ frontend react.js code in a separate folder. I have it set up to where the server is listening on local host:4000 and the client is listening on 3000, I have connected the front end and back end in my app.js using this line of code..

const socket = io.connect('http://localhost:4000');

I am curious as to what this means. does it mean that when I deploy my website that it will be hosting my server from my computer? Does it mean that it will be hosting the sockets from the client's computers? is the localhost:4000 used for testing purposes and will need to be changed later upon deployment of the website? If none of these are correct, any explanation would be greatly appreciated. If my code is fine the way it is and will not need to be changed upon deployment of my website, please let me know.

Thank you to anyone who can help!!!

Answer 1

does it mean that when I deploy my website that it will be hosting my server from my computer?

It means it will try to connect to a Socket.io server running on the same computer as the browser is running on.

This will usually fail. (Your development environment is an exception because you are running both browser and server on the same computer).

is the localhost:4000 used for testing purposes and will need to be changed later upon deployment of the website?

Yes.