Hi,
Just to be clear, you are hosting a node server with socket.io and you’re trying to make a connection to it for real-time communication, primarily through websockets. I don’t see any proxy redirects setup on your current deploy so I assume you are trying to connect directly to it from your client app. This request doesn’t pass through netlify, the connection goes straight from the client browser to the backend, which means you should probably check your server logs to see what’s happening.
Can you provide more details on what’s wrong as well as a link to a page where you are seeing the error so others can check it out? Thanks.