How to properly set backend addresses in React app for Heroku?

Question

JavaScript

I have a react app and a node.js server which is a rest server on port 5000 and a websocket server on port 7000.
Everything works locally, the application connects to the localhost.
There is a problem on heroku, the rest server works, but only if accessed without specifying a port. It is impossible to connect to the websocket server with or without a port.
How to properly set up such a link?